Sekretarz Redakcji – Secretary – Kazimierz Kęsik
Rada Konsultacyjna – Advisory Board Pavel Cermak, Havlickuv Brod, Czech Republic Tadeusz Filipek, Lublin, Poland
Gyorgy Fuleky, Godollo, Hungary Witold Grzebisz, Poznan, Poland Janusz Igras, Puławy, Poland
Stanisław Kalembasa, Siedlce, Poland Jakab Loch, Debrecen, Hangary Jan Łabętowicz, Warszawa, Poland, Ewald Schnug, Braunschweig, Germany
Monograph
Effect of fertilizing systems supporting nitrogen use efficiency on maize yield development
Jarosław Potarzycki
Reviewer Jerzy Księżak, Puławy, Poland
Copyright by Polish Fertilizer Society – CIEC ISSN 1509-8095
Adres Redakcji
Zakład Żywienia Roslin I Nawozenia IUNG-PIB Czartoryskich 8, 24-100 Pulawy, Poland
e-mail <nawfert@iung.pulawy.pl>
www: nawfert.pl Printed: IUNG-PIB Pulawy, 200 copies, B-5
Nr 39/2010
Contents
1. Potarzycki, J. Improving nitrogen use efficiency of maize by better fertilizing practices. Review paper ...5 2. Potarzycki, J. Yield forming effect of zinc and magnesium applied as supplements
of the NPK fertilizer to maize cultivated in monoculture ...25 3. Potarzycki, J. Yield forming effect of combined application of magnesium,
sulphur and zinc in maize fertilization ...44 4. Potarzycki, J. Effect of increased input of fertilizers balancing nitrogen on
nutrients accumulation by maize at maturity ...60 5. Potarzycki, J. The impact of fertilization systems on zinc management by
maize ...78 6. Potarzycki, J. Influence of balanced fertilization on nutritional status of maize at
anthesis ...90 7. Potarzycki, J. Yield forming functions of zinc in maize crop Review paper ...109
Maize is a crop characterized by a very high yield potential, which is expressed both by biomass production as well as grain yield. Modern varieties of maize are characterized by considerably high resistance to abiotic environmental factors. Therefore, it is widely cultivated in temperate climate zones. This is why the crop is very useful in food and feedstuff production. At present, maize is also considered to be one of the important renewable energy carriers.
Formation of maize yield due to the fixed number of plants per unit field area, already at planting is simplified in comparison to other cereals. This crop development can be split in two periods. The first one extending from tasselling to water stage of kernel’s growth is called the critical window of yield formation. This period which defines the potential grain yield, is significantly affected by external factors, i.e, water and nutrients supply. The second main period of yield development, ripening is to a great extent dependent on the type of variety, classical or stay-green. Accumulation of dry matter by growing cob of a classical variety depends on both, current photosynthesis of leaves as well as on assimilates remobilized from pre-anthesis resources accumulated in stem and leaves. Yield development by a stay-green variety is meanwhile more affected by the photosynthetic activity of current leaves. Therefore, fertilizing strategy of modern maize varieties aimed at the higher greenness of leaves, considered as a plant organ supplying assimilates both to developing kernels and roots, is much more sophisticated.
The most efficient fertilization practices are aimed at balancing nitrogen by other mineral nutrients, especially magnesium, sulfurs and zinc. The date in the literature usually focuses on the specific yield-forming functions of these nutrients. However, they rarely explain how particular nutrients interact in the process of determining the nitrogen supply to maize canopy during critical stages of yield formation and in increasing nitrogen use efficiency.
In the last decade, the author of this monograph has participated in a series of research studies carried on at the Department of Agricultural Chemistry and Environmental Biogeochemistry, University of Life Sciences in Poznań. The aim of these researches was to explain the role of secondary nutrients and zinc in fertilization of maize, supplied with different rates of nitrogen. The scope and subject of the research are innovative not only in Poland but also in the Central-Eastern Europe with similar climate conditions.
In the presented monograph author evaluates nutrient balance status of maize at anthesis and, on this base, tries to predict the final grain yield. Following the assumption that the concentration and distribution of mineral nutrients between plant organs reflect ex post conditions during vegetation, maize nutrient status was also subjected to a post- harvest evaluation (at the stage of full maturity of kernels). This served as the basis for developing the hierarchy of yield forming roles of each micronutrient in different maize fertilization systems.
Zinc fertilization of maize has been a subject of research studies for a long time.
However, in this monograph the role of this particular micronutrient in relation to specific critical stages of yield formation of maize is discussed. It has been recognized that the role of zinc is very complex as it depends on both zinc source and accompanying ions as well as on the level of nitrogen nutrition in plants. Thus the study presented in the including papers may become a basis for developing precise recommendations as regards zinc fertilization.
Jarosław Potarzycki
FERTILIZING PRACTICES Review
Jarosław Potarzycki
University of Life Sciences, Poznań, Poland
Abstract
Nitrogen use efficiency (NUE) in maize production in Poland is unsatisfactory, achieving for the period 1992-2008 level of 75 kg grain∙ kg N-1, whereas its maximum is much higher, amounting to 105 kg grain∙ kg N-1. Nitrogen use efficiency, NUE, is an index relating the harvested yield (biomass, grain) to a unit of nitrogen supply and/or assimilated in the harvested yield. Taking into consideration the whole course of plant growth this index can be split into three sub-units: nitrogen uptake efficiency, NUPE, nitrogen utilization efficiency, NUTE, nitrogen remobilization efficiency, NREE. There are two main ways for NUE improvement, breeding new, more efficient varieties and introducing better fertilizing practices. The first strategy requires full understanding the genetic backgrounds of nitrogen uptake by roots and nitrogen functions in increasing radiation use efficiency. The second strategy of NUE improvement relies on maize crop growth environment modification (soil pH, overall fertility level improvement) and on optimizing N rates and on balancing N with other nutrients supply. Band phosphorus application and soil or foliar application of magnesium, sulfur and zinc create fertilizing bases for substantially increase of nitrogen use efficiency.
K e y w o r d s: maize, nitrogen use efficiency (NUE), stripe phosphorous application, foliar/soil magnesium application, foliar zinc application
Potential, maximum and actual yields
Potential yield of maize crop based on the amount of radiation is evaluated at the level of 32 t ha-1. Yielding potential of current varieties grown inthe U.S. is at the level of 20 t∙ ha-1 [Tollenaar and Lee 2002], but actual yields in the years 2008-2009, were at the level of ca 10,0 t∙ha-1 [FAOSTAT]. The record yield of maize in the U.S., grown in rain-fed conditions, amounted to 23,5 t ha-1. This yield was accomplished by using stay-green maize variety cultivated in monoculture with huge amounts of N, P, K and S fertilizers on fertile soil and by full recycling of post-harvest residues [Reetz 2000].
In Poland yield potential of grain maize, due to climatic conditions is much lower than in the U.S., reaching 20 t∙ ha-1 [Grzebisz 2008]. Attainable productivity of varieties, grown in assessment trials in the years 2008-2009 was at the level of 10,8 t∙
ha-1 [COBORU 2010]. The actual grain yields, harvested by farmers are much lower, reached in these years on average 6,0 t ha-1 [FAOSTAT, GUS 2010]. According to Księżak [2008] the main factors affecting mostly maize production in Poland are as follows: index of agricultural production area valorization, poultry and pig stocks.
Trend of actual maize yields in the period 1992-2008 showed, however an annual rate increase of 99 kg grain∙ ha-1. This positive trend situates Poland in the progressive group of maize producers, indirectly indicating favorable growth conditions for this crop [Hafner, 2003].
In spite of positive trend of yield increment, there is still a wide gap between potential, i.e. attainable yields of maize as recorded by COBORU [2010] for currently grown varieties and actual maize yields in Poland. However, the attainable yield level is corrected by site specifi c conditions explicitly defi ned by supply of water (year effect - considered as a precipitation course) and supply of nitrogen.
Both factors defi ne maximum yield of each crop, which are year-to-year variable.
In order to calculate maximum yields of maize and yields a gap the concept of the partial factor productivity (PFP) has been applied [Cassman, et al., 2002]. This index expresses the amount of crop productivity (unit/ha) per unit of nutrient applied in fertilizer (Grzebisz et al., 2009). The partial factor of fertilizer nitrogen productivity index (PFPN) in Poland, as averaged over 1986-2008 period was at the level of 75,5 kg grain per 1 kg of applied N fertilizer [FAOSTAT, GUS 2010]. However, its top productivity as evaluated for the fourth quarter (top quartile) was by 36% higher,
Fig. 1. Trends of actual and maximum yields of maize in Poland, years 1992-2008 [FAOSTAT, GUS 2009]; Legend: Y-R – actual yields Y-M – maximum yields
amounting to ca 105 kg grain per kg N. This second index value reflects during the period 1992-2005 growth conditions favorable to maize production. Therefore, it has been used to calculate maximum yields for the 1992-2008 period (Fig. 1). The annual grain yield increase in this period amounted to 99 kg ha-1 but theoretically it could increase at the level of 270 t ha-1. Based on the top unit nitrogen productivity the maximum yield of maize grain in Poland can be set at the level of ca 8,5 t ha-1. At the beginning of the period 1992-2008, the yield gap amounted to 1,35 t ha-1, but it raised up at the end of the period to 3,7 t ha. These two numbers, in spite of increasing yield trend, indicate the occurrence of some factors significantly limiting nitrogen fertilizer productivity. There are some sets of well known factors causing N imbalance, in turn inhibiting growth and maize crop yields in Poland.
Maize is a crop highly tolerable to slightly acid growth conditions, but it is highly sensitive to phosphorus supply, particularly at the beginning of vegetation. The same refers to other nutrients, especially to potassium, but also to magnesium, sulfur, zinc and boron. Soils in Poland are generally poor in available forms of these nutrients.
Amounts of main nutrients applied as fertilizers based on yearly country data are highly imbalanced [FAOSTAT]. During the last decade, the N: P2O5: K2O ratio is almost constant at the level of ca 1:0,3:0.40, whereas physiologically established ratio of these nutrients in biomass of high yielding maize crop at harvest amounts to 1:0,45:1,0(1,2) [GUS, 2001; Grzebisz 2009, Grzebisz et al. 2010]. All these growth factors due to imbalanced supply of fertilizer nitrogen are responsible for lowering nitrogen unit productivity (PFPN). The result of this situation is the low yield of grain maize, in additionally showing high-year-to-year variability.
Nitrogen use efficiency, NUE – definition and indices
The nitrogen use efficiency is the main index for evaluation the crop production system related both to production quantity and environment safety [Cassman et al.
2002]. Moll et al., [1982] defined NUE as the yield of grain per unit of available N in the soil (including the residual N present in the soil and the fertilizer). The term available nitrogen encompasses at least, two nitrogen pools, soil nitrogen pool, and fertilizer pool. The first one is difficult for quantitative determination and its measure is usually the amount of nitrogen accumulated by plants grown on plots without N application (control plots or parcels). A good approximation of this pool offers the content of mineral nitrogen Nmin in the soil profile [Pecio et al., 2009]. The second component, fertilizer pool is directly related to the amount of fertilizer nitrogen applied to the currently grown crop during its vegetative season.
According to Moll et al., [1982] the NUE can be divided into two indices:
uptake efficiency NupE as the ability of the plant to remove N from the soil in forms of nitrate and ammonium ions and the utilization efficiency NutE as the crop ability to use taken up N to produce grain yield. Author of this review distinguish third
index, nitrogen remobilization efficiency NreE as the contribution of pre-anthesis accumulated N to final grain N yield.
The operational procedures to evaluate indices of nitrogen use efficiency require well defined components such as: plant biomass (B), grain yield (GY), total N uptake (Ntup), total N supply (Ntsp), soil N supply (Nsp), fertilizer N applied (Nf). General algorithms describing basic indices are as follows:
1) NupE = Ntup/Ntsp 2) NutE = GY/Ntup
Using experimental data the basic indices can be revaluated into practical algorithms assessing efficiency of N fertilizer nitrogen as presented by the following formulas:
3) Agronomic N efficiency, ANE = (GYNf - GYN0)/Nf (kg grain ∙ kg Nf);
Physiological N efficiency, PNE = GYNf - GYN0)/(NtupNf - NtupNN0); (kg grain ∙ kg Nf) 4) Nitrogen apparent recovery, NAR = [(NtupNf - NtupNN0)/Nf] ∙ 100%, or
NAR=PNE/ANE
where: GY- grain yield, kg ha-1;N0- the N non-fertilized (control) plot, Nf- the N fertilized plot.
The third index, nitrogen remobilization efficiency (NreE), includes a set of measures to describe nitrogen economy of maize crop during grain filling period, nitrogen remobilization NR, (kg ∙ ha-1), nitrogen remobilization efficiency NRE, (%), post-anthesis nitrogen gains or losses PANU, (kg ∙ ha-1), efficiency of post-anthesis nitrogen uptake PANUE(%), nitrogen harvest index NHI,(%). The algorithms describing these indices are as follows:
5) NR= Nat - Nhvv 6) NRE = NR/Nat ∙ 100 7) PANU = Nhvtot - Nat
8) PANUE = PANU/Nat ∙ 100 9) NHI = Nhvg/ Nhvtot ∙ 100, where:
Nat – nitrogen content in plants at anthesis (kg ∙ ha-1), Nhvv – nitrogen content in vegetative plant organs at maturity (kg ∙ ha-1), Nhvtot – total nitrogen content in plant at maturity, Nhvg – nitrogen content in grain (kg ∙ ha-1).
Critical stages of maize response to nitrogen supply
Plant growth analysis, based on dynamics of dry matter accumulation, is a very useful method for discriminating the most sensitive stages of maize response to external factors, including supply of nitrogen and other nutrients. The rate of dry matter accumulation by maize plant in the growing season depends on nitrogen supply. As shown in Fig. 2, curves describing the nitrogen uptake rate (NUR) and the crop growth rate (CGR) elevate in two distinct, time-separated stages of maize growth.
The first peak, smaller one, which could be termed as the primary indicator of maize response to nitrogen supply, reveals itself at early stages of this crop growth, i.e., from BBCH17 to 19. Dry matter accumulation rate follows, as presented by the CGR curve, the course of nitrogen accumulation. The second peak of nitrogen uptake, which could be termed as secondary or the major one, occurs at the onset of flowering. Within a period lasting ca 10 days, i.e., from late tasselling (BBCH55-59) till full flowering (BBCH65), the rate of nitrogen accumulation by maize crop doubles itself. However, this elevated maize crop N status is short and temporary, dropping down at the milky stage to former, i.e. pre-anthesis rate of nitrogen accumulation.
The CGR course follows the pattern of nitrogen accumulation, reaching a peak at the same stage of maize growth. However, the post flowering rate decline is much
Fig. 2. Dynamics of nitrogen and dry matter accumulation by maize canopy during the course of the growing season [based on Grzebisz at al., 2008a]
Legend: NUR – nitrogen uptake rate, CGR – crop growth rate
gentle, ending at the early dough stage of maize growth, i.e. when kernels contain ca 45% dry matter.
Another analytical procedure for discriminating the most sensitive stages of maize response to external factors, including supply of nitrogen and other nutrients is an analysis of the yield components. Maize grain yield is a function of three basic yield components such as the number of cobs per hectare (NC), number of kernels per cob (NKC) and thousand kernels weight (TKW). The main components of NKC are number of rows per cob (NRC) and number of kernels per row (NKR). The component, NC is in a fact established at sowing, assuming one cob per plant, and it can be passed over. The development of other components, results from nitrogen supply in the course of the vegetation season, which in turn depends on other external growth factors (Table 1).
Table 1. Critical stages of structural components of maize yield formation in the course of the growing season (based on Grzebisz, 2008)
Yield structural
component Growth stage BBCH
Factors limiting development of yield components
Nutrient Others
Ears initiation 13-15 N, P, Mg, Zn low temperatures
NRC 16-50 N, K, Mg drought
NKR 50-69 N, K, B, Zn drought
NKC 16-71 N, K, Mg, B, Zn, drought, heat stress
TKW 72-89 N, P, Mg, Zn extremely high temperatures
The maize grain yield development begins since the three leaves stage (BBCH13), initiated by leaves and ears (i.e. cobs) primordia formation. This primary for final yield process is completed at the stage of BBCH15. At this early period of maize plant growth, potential number of leaves and ears with spikelet primordia are established [Viet et al., 1993]. That is probably the main reason of sudden increase of maize plant requirement for nitrogen supply, which takes place in the period extended from BBCH7 to BBCH9 (Fig. 2). As reported by Subedi and Ma (2005) insufficient supply of nitrogen up to the stage of BBCH18 negatively affects diameter of an ear, its length and potential number of kernels per an ear. Potential number of flowers developed by maize ear can be as high as 1000 but number of kernels at full maturity (black stage) is much lower, seldom exceeding 500 per cob. The reduction process begins at early stages of plant growth, during spikelet initiation. The primary yield forming components, number rows per cob, NRC, depends on the efficiency of primordium initial transformation into paired spikelets [Veit et al., 1993]. Therefore, NRC is considered as a highly conservative, inherent genetic characteristic of the
developing maize ear during the season. However, under conditions of severe stress, mainly abiotic (water shortage, low nutrients supply) number of rows is limited, negatively affecting final grain yield [Ritche and Alagarswamy 2003]. The second characteristic of a maize cob, number of kernels per row, NKR, shows, however, a very high response to external factors, such as water and nutrient availability [Potarzycki and Grzebisz 2009].
Kernel number per cob, NKC is a basic component of maize crop yield structure. The decisive period for this element formation begins one week before silking, BBCH51 and finishes four weeks later, i.e. at the blister stage (BBCH71) (Jones et al., 1996). The main, responsible factors in this period are the total sum of physiologically active temperatures, rate of dry matter accumulation, rate of nitrogen supply, rate of water supply. The required sum of temperatures, within this particular period of maize crop development, termed as “critical window”, amounts to 327 oC days (based on t > 8 oC), divided into 227 and 100 oC, before and after silking, respectively [Ritche and Alagarswamy, 2003]. This sum of temperatures allows, with sufficient supply of water and nitrogen, to reach by a maize plant canopy high growth rate [Paponov et al. 2005, Uhart and Andrade 1995, see also Fig. 2). Therefore, any external factor decreasing supply of nitrogen during silking and blister stage in turn decreases the number of kernels per cob.
The last component of the yield structure, thousand kernel weight, TKW, should be considered in the light of the sink/source concept. Sink size defines the ability of developing maize ear, i.e. cob to accumulate nitrogen and assimilates and source the ability of maize vegetative parts to supply of nitrogen and assimilates to the growing cob [Uhart and Andrade, 1995, Cazetta et al. 1999]. The first sub-unit of sink size refers to final number of kernels, established until the end of the blister stage, which depends mostly on water, potassium and boron supply in the “critical window” of maize growth. The second sub-unit of sink size is determined by an individual kernel capacity for dry matter accumulation, which reveals at blister stage. Amount of nitrogen supplied at this stage affects the rate and extent of endosperm cell division and starch granules initiation [Jones at al. 1996]. The source size is responsible both for carbohydrates production during reproductive stages of maize growth, termed as grain filling period and depends on factors responsible for leaf duration and also by rate of nitrogen and assimilates remobilization from vegetative maize parts [Rajcan i Tollenaar 1999, Pommel et al. 2006]. Maize plant well supplied with zinc is able to extend leaves duration, i.e. extending length of leaves assimilation period, which are also capable to increase their own rate of photosynthesis [Guliev et al., 1992].
NUE improvement by breeding new maize varieties
There are two main strategies for improvement nitrogen use efficiency by crop plant. The first one relies on main routs of nitrogen uptake and transformation within the plant. The second one requires an improvement of plant crop growth environment
through optimizing conditions of nutrients uptake, including nitrogen. Therefore, the crop and environment oriented strategy of improvement nitrogen use efficiency is supported by implementation of new maize cultivars, and more efficient management of fertilizer nitrogen applied for maize [Cassman et al. 2002, Hirel et al. 2007].
Breeding studies on maize, conducted both in the tropics and in temperate areas of the World revealed a diversity in N-use efficiency among local, old and new maize varieties, when cultivated on soils poor in nitrogen, or under conditions of low input of external nitrogen [Baenziger et al. 1997, Bertin and Gallais 2000, Ma et al. 1999]. As reported by Paponov et al., [2005] the genotypes selected for high N- use efficiency could sustain the sufficiently high number of kernels per plant under stress conditions. However, field studies, conducted with new, N efficient cultivars, showed a pronounced grain yield reduction, when compared to classical varieties, or when cultivated on soils with high N input. Therefore, taking these negative yield results into account, breeders have established a tolerable yield reduction limit at the level of 35-40% for the N efficient cultivars [Gallais and Coque, 2005].
Maize breeding programs conducted under conditions of low N availability have to take into account three, already mentioned main components of NUE, related to main genetic traits, nitrogen uptake NupE, N assimilation NutE and biomass production and N reallocation into kernels during the filling period, NreE.
The first component NupE depends mainly on the maize plant ability to take up soil nitrogen. In this process root system plays a crucial role, especially on soils poor in available nutrients, including nitrogen [Peng et al. 2010]. Hence, efforts of breeders are orienting mainly on modification the maize plant root morphology towards increasing density of plant roots also in deeper soil layers and increasing specific root length (root DM per unit of root length) (King et al., 2003). Other sets of plant modifications refers to increasing biomass production during the vegetative period of maize growth and to N reallocation efficiency during grain filling from vegetative tissues (stem, leaves, roots) to growing kernels [Ta and Weiland 1992]. The first group of traits linked to NutE requires insight into the assimilation mechanizm of N coupled to photosynthesis. However, it is an extremely conservative element of maize plant metabolism, and many breeding programs consider two potentially suitable plant features such as specific leaf area and some enzyme activities. Among many tested enzymes, glutamine synthetase (GS), as deeply involved in many steps of plant nitrogen economy, is nowadays considered as the important genetic trait for explaining variability of N-use efficiency of cultivars grown under different N input (Gallais and Hirel, 2004). Another possibility of NutE improvement relates to modification of N leaf economy, oriented on increasing capture of solar radiation by plant grown under low N input [Hirel at al. 2007].
NUE improvement through nitrogen-balanced management
In the growing season nitrogen requirements are modified by both primary (light intensity, temperature, water and nitrogen supply) and secondary (availability of other nutrients, diseases) factors. An extended study on maize grain production in Canada showed following order of yield limiting factors, weed infestation (27-38%)
> lack of pre-plant N application (1-22%) > low plant population density (8-13%) and lack of K (up to 13%), manganese (up to 12%) and zinc (up to 10%) application [Subedi and Ma, 2009].
For maize growers the most important production target is to keep the optimum rates of biomass accumulation by a maize canopy during the growing season, as a prerequisite of full development of yield structure components. Therefore, an agronomical efficient and environmentally friendly maize crop fertilizing system requires the new sets of measures, leading to improvement in N-use efficiency.
The holistic strategy of N canopy management should comprise three compatible steps, primary (all measures related to factors controlling maize root growth as a prerequisite of nutrient uptake), basic (all measures related to backgrounds of nitrogen application) and secondary (all measures for effective balancing fertilizer N, addressed mainly to other nutrients supply). In the last few decades, the second and the third set of measures had been deeply worked out by scientists and successfully introduced into farming practice, at least partly.
Nitrogen
The above mentioned three sets of measures should be focused on delivery to maize plant an appropriate amount of nitrogen during each critical stage of yield formation, i.e. keeping nitrogen critical concentration over the course of vegetation.
As presented in Fig. 2 the rate of maize canopy growth CGR, depends on the rate of nitrogen accumulation NUR, which in turn is decisive for nitrogen concentration in vegetative tissues. The concept of critical N concentration assumes that at any time of plant vegetative growth a defined N concentration is required, in turn allowing the crop to reach maximum biomass production. The critical N concentration algorithm for maize as developed by Plenet i Lemaire [1999] is presented below:
Nc = 3.4 ∙ W-0.39 where:
Nc - critical plant N concentration, % DM;
3,4 - nitrogen concentration in plant biomass, when W = 1.0 t ha-1; W - dry matter yield of maize canopy, t ha-1;
-0.39 - slope of regression curve
This equation describing so called critical dilution curve informs that throughout maize vegetation and dry matter accumulation the minimum N concentration
decreases in accordance to the power function [Davienne-Barret et al. 2000].
However, the most important part of this function with respect to efficient fertilizing practice in maize crop relates to its development period of biomass below 1,0 t DM ha-1. Therefore, the above equation is, in fact, unsuitable for making any nutritional correction in nitrogen status in maize crop at early stages if its development. It has been calculated that the well-fed maize canopy reaches biomass of about 1 t DM at the stage of BBCH17/19. As described above, at this particular stage, the primary components of maize yield structure are under strong dependence on plant nitrogen nutritional status [Subedi and Ma, 2005; Grzebisz et al., 2008]. Therefore, for full exploitation of maize production potential, any fertilizing efforts oriented on plant N corrections should precede this stage. Hence, the most important nitrogen management target is to detect a critical N concentration at young stages of maize growth up to the BBCH15. This concept as presented in Fig. 3 shows that at early stages of maize growth the measured N concentrations for high-yielding plantations fits fairly well power function. The constant of the developed algorithm is also close to 3.4, i.e. presenting the same level as found by Plenet i Lemaire [1999]. Hence, the critical N concentration in the maize canopy at the stage from the tree to five leaves at very early stages is a new fertilizing target. It must be established at much higher level, for example, from 4.0 to 4.4% as shown in Fig. 3.
Fig. 3. Critical nitrogen dilution curve for maize canopy et early stages of growth [based on Kruczek, 2005a]
The maize fertilizer strategy oriented on NUE improvement should be therefore, supported by an establishment of optimum N rate, type and timing of N fertilizer application and methods of N fertilizer application. The efforts to determine an optimum N rate for maize are complicated, as results from the following theoretically developed algorithm:
FRN = [(Y ∙ Nu) – (Nmin + Nc + Ns)]/NfE where:
FRN - N fertilizer rate, kg N ha-1; Y - yield of grain, t ha-1; Nu - N specific uptake, kg N t-1;
Nmin - mineral N content in 0-90 cm soil layer, kg N ha-1; Nc - N soil credit, kg N ha-1;
Ns - soil mineralizable N, kg N ha-1 y-1;
NfE - efficiency of fertilizer N, coefficient < 1,0.
Because of uncertainties of most of the presented algorithm parameters recommended rates of N fertilizers are based mainly on experimental data and so far one of the most important sources of data are production functions [Fotyma E.
1994, Kruczek 2005b]. In spite of limitation of experimental data, they allow making a crude estimation of the optimum N rate ranges for defined growth conditions.
However, the experimentally established optimum N rates for high yielding fields are as a rule much lower than frequently applied in farming practice. According to Fotyma (1994) and Kruczek (1997) the optimum N rate, considering soil quality and amount of precipitation during the growing season, should be in the range 90 to 130 kg N ha-1.
The second prerequisite of effective nitrogen application is a proper selection of N fertilizer and its timing. In optimal soil conditions (as indicated by sufficiently high K and P soil fertility level) the best source of nitrogen proved to be ammonium nitrate (Fig. 4). The advantages of this fertilizer are related to nitrate form of nitrogen, easily taken up by maize [Davienne-Barret et al. 2000, Imsande and Touraine 1994].
Nitrogen fertilizers did differ not only in the optimum N rate and final grain yield but also in unit N productivity PFPN. The greatest differences in this index were found at the lowest N rate of 25 kg N ha-1 in the orderUR>AN >NPK, while at the optimum N rate PFPN was much lower and ranked in order AN>UR>NPK [Fig. 4]. It must be hence stressed upon conflicting character of PFPN and optimal N rate securing optimal maize yield. As presented in the Fig. 5 the highest values of PFPN were attributed to N lowest rate resulting, however in the lowest yields. As described in the first chapter of this article in the top quartile (for the years1992-2008) the average
PFPN in Poland was at the level of 105 kg grain ∙ 1 kg-1 N. For this particular value the required N rate amounts to ca 85 kg N ha-1 in order to achieve yield of grain at the level of 85-90% of the yield in maize varieties testing trials [COBORU 2010].
Fig. 5. Partial factor productivity of fertilizer nitrogen (PFPN) as a function of N rates [based on Fig. 4]
Fig. 4. Effect of fertilizer nitrogen type on its optimum rate [based on Kruczek, 2005b]
Legend: UR – urea, AN – ammonium nitrate, NPK – complex NPK fertilizer
Phosphorus
Phosphorus is a crucial nutrient for maize plants, particularly in two growth stages. The first reveals before stage BBCH18 (see Fig. 2) and is mostly induced by low soil temperature, that limit P uptake by maize roots. The second, major one reveals during the grain filling period. At that particular stage high demand of maize plant for phosphorus is a result of very high rate of dry matter accumulation by the growing cob [Grzebisz et al., 2008a]. These two critical stages of maize crop response to supply of phosphorus must be taken in consideration in fertilizing system. Young maize plants before the stage of eight leaves(BBCH18), even grown on soil rich in phosphorus, show a high response to fresh applied P fertilizers (Fig. 6).
This response was a reason for developing a sophisticated fertilizing technique, generally known as starter fertilization. It is defined as applications of low P rates in stripes close to seed placement, which in turn brings about higher nutrient concentration in a soil zone penetrated by roots of maize plant (Lu and Miller, 1993).
This technique of phosphorus fertilizer application can be successfully used both in poor and P-fertile soils and a part of phosphorus promotes also other nutrients uptake by plants [Kruczek 2005a]. The most important advantage of this technique is better crop performance in the early stage of growth, particularly in unfavorable weather conditions. However, final grain yield response to localized application of P fertilizer depends on many other growth factors, which reveal their activity in the course of
Fig. 6. Effect of phosphorus fertilizer rates on maize seedling biomass at BBCH17 [source of primary data: Lu and Miller 1993 and Kruczek, 2005a]
maize vegetation [Dubas and .Duhr 1983]. Even at the low yield increase, the most important advantage of starter fertilization is lower consumption of P fertilizers and slightly higher content of dry matter in kernels (Tab. 2).
Table 2. Economic evaluation of the strip system of phosphorus fertilizer application to maize crop [Michalski, Kowalik 2007]
Evaluated parameter Size of change Unit cost Financial result PLN∙ha-1
Yield increase, t ∙ ha-1 + 0,2 50 PLN + 100
Grain moisture - 1,0% 10 PLN ∙ t-1 ∙ 10 t + 100
Total P and K fertilizer
application before sowing Lack of Autumn
P and K fertilizing 30-50 PLN + 30-50
Decreased P rate - 30 kg ∙ ha-1 2 PLN kg-1 + 60
- 60 kg ∙ ha-1 + 120
Summary - - + 290-370
The better choice for this method of phosphorus application is ammonium phosphate than calcium phosphate [Dachler and Koechl 1995, Kruczek 2005b, Michalski and Kowalik 2007]. For basic (before sowing) fertilization of maize single superphosphate SSP gives better results than triple superphosphate TSP and partially acidulated phosphoric rock PAPR [ Potarzycki 2009] (Tab 3).
Table 3. Effect of phosphorus fertilizer type on nitrogen use efficiency parameters [Potarzycki 2009]
Nitrogen rate
kg N ∙ ha-1 Type of P fertilizer 1 Average for
N rate Control - NK NPK- PAPR NPK-SSP NPK-TSP
Agronomical efficiency2kg grain ∙ kg N-1
80 16.7 25.4 29.2 25.9 24.3
140 13.6 20.6 21.1 21.1 19.2
Average for P
fertilizer 15.2 23.0 25.4 23.5 -
Nitrogen recovery %
80 54 74 74 72 68
140 62 58 56 46 55
Average for P
fertilizer 68 66 64 50 -
1 Legend: PAPR – partially acidulated phosphoric rock, SSP – single superphosphate, TSP triple superphosphate
Sulfur and magnesium
Maize crop fertilization with magnesium and sulfur is not yet well scientifically worked out. The main reason is a generally low maize crop requirement for both nutrients [Grzebisz 2009]. However, on soils poor in available magnesium, insufficient supply of these nutrients can exert a significant negative effect on nitrogen use efficiency. It is well recognized that increasing rates of fertilizer nitrogen results in NUE declining [Fotyma 2003, Szulc 2010]. Including magnesium and/or sulfur into the maize fertilization program, even on magnesium rich soils may substantially increase nitrogen unit productivity (PFPN) and in turn grain yield (Fig. 7).
Fig. 7. Effect of balanced maize fertilization with nitrogen on grain yield [based on Baráóg and Frąckowiak-Pawlak, 2008]);
7,6 7,8 8 8,2 8,4 8,6 8,8 9 9,2 9,4 9,6
210 240 260
mazie varieties, FAO number
yield of grain, t ha-1
NPK NPK+MgS
Zinc
Maize is considered as crop sensitive to deficiency of boron and zinc [Alloway 2008, Facenko and Lożek 1998, Potarzycki and Grzebisz 2009, Wrońska et al. 2007, 2007a]. The highest relative zinc uptake rate throughout maize growth takes place at the stage of BBCH15-16 [Grzebisz et al., 2008b] preceding the first culmination peak of nitrogen uptake (see Fig. 2). The foliar applied fertilizer zinc causes an increase of the nitrogen uptake rate, and in turn affects dry matter accumulation rate (Fig. 8). The most striking effect of foliar added zinc is, however, the extended period of nitrogen accumulation in the post-anthesis period of maize growth. Yield forming effect of zinc can be therefore, related both to increasing sink and source capacity of maize during reproductive growth. The first one, sink relates to significant increase of the number of kernel per cob (NKC) (Table 4).
Fig. 1. Trends of actual and maximum yields of maize in Poland, years 1992-2008 [FAOSTAT, GUS 2009]; Legend: Y-R – actual
yields Y-M – maximum yields
Fig. 7. Effect of balanced maize fertilization with nitrogen on grain yield [based on Barłóg and Frąckowiak-Pawlak, 2008]);
Fig. 8. Effect of zinc foliar application on dynamics of crop nitrogen uptake rate (CNUR) by maize canopy in the course of the growing season [based on Grzebisz et al., 2008a]
0 100 200 300 400 500 600 700 800
14 17 19 39 59 67 75 83 87 89
growth stages, BBCH scale CNUR, mg m-2 d-1
0 1 Zn rate kg ha-1
Table 4. Effect of zinc foliar application on maize yield structure components [Potarzycki, Grzebisz 2009]
Zinc rates kg Zn ha-1
Cob length (CL)
Number of rows on the cob (NRC)
Number of kernels in the
row (NKR)
Number of kernels in the
cob (NKC)
Thousand kernel weight
(TKW)
cm Number g
0 13.88 14.66 27.76 407.0 253.4
0.5 15.37 15.00 29.20 438.0 266.1
1.0 15.72 15.13 31.69 479.5 264.3
1.5 15.19 15.04 29.37 441.7 275.0
LSD 0.05 0.424 n.s. 2.319 34.30 9.74
Its primary reason is probably an extra supply of nitrogen to developing cob, which takes place at young stages, before the BBCH18 [Subedi and Ma 2005]. It finally results in a higher number of kernels per a cob at the blister stage, in turn increasing its demand for carbohydrates supply. The second maize capacity component fulfilling at reproductive growth, source, refers to leaves potential for supplying carbohydrates.
The activity of carbonate anhydrase depends on zinc supply [Guliev 1992]. The yield forming effect of zinc on maize source capacity reveals therefore through increasing weight of individual kernels, i.e. higher weight of thousand kernels (Table 4).
Fig. 8. Effect of zinc foliar application on dynamics of crop nitrogen uptake rate (CNUR) by maize canopy in the course of the growing season [based on Grzebisz et al., 2008a]
As reported by Wrońska at al., [2007a] grain yield of maize crop can be substantially increased by foliar application of zinc in the rate ranging from 0,5 to 1,5 kg ha-1t The optimum time of this nutrient application extends from sowing up to the stage of BBCH 15(16). Zinc supply to maize crop gives the best results at low N rates, i.e.
below 100 kg N ha-1 [Wrońska at al.,2007a, Potarzycki and Grzebisz 2009].
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Corresponding author:
Dr. Jarosław Potarzycki, University of Life Sciences, Department of Agricultural Chemistry,
Wojska Polskiego 71F, 60-625 Poznań, Poland e-mail: jarekpo@up.poznan.pl
Fig. 1. Trends of actual and maximum yields of maize in Poland, years 1992-2008 [FAOSTAT, GUS 2009]; Legend: Y-R – actual yields Y-M – maximum yields
Fig. 2. Dynamics of nitrogen and dry matter accumulation by maize canopy during the course of the growing season [based on Grzebisz at al., 2008a] Legend:NUR – nitrogen uptake rate ,CGR – crop growth rate
Fig. 3. Critical nitrogen dilution curve for maize canopy et early stages of growth [based on Kruczek, 2005a]
Fig. 4. Effect of fertilizer nitrogen type on its optimum rate [based on Kruczek, 2005b]Legend: UR – urea , AN – ammonium nitrate, NPK – complex NPK fertilizer
Fig. 5. Partial factor productivity of fertilizer nitrogen (PFPN) as a function of N rates [based on Fig. 4]
Fig. 6. Effect of phosphorus fertilizer rates on maize seedling biomass at BBCH17 [source of primary data: Lu and Miller 1993 and Kruczek, 2005a]
Fig. 7. Effect of balanced maize fertilization with nitrogen on grain yield [based on Barłóg and Frąckowiak-Pawlak, 2008]);
Fig. 8. Effect of zinc foliar application on dynamics of crop nitrogen uptake rate (CNUR) by maize canopy in the course of the growing season [based on Grzebisz et al., 2008a]
AS SUPPLEMENTS OF THE NPK FERTILIZER TO MAIZE CULTIVATED IN MONOCULTURE
Jarosław Potarzycki
Poznan University of Life Sciences, Poznań, Poland
Abstract
Field trials with maize (var. FAO 240) cultivated in monoculture were carried out in five consecutive growth seasons from 2003 to 2007. The aim of the work was to evaluate the yielding response of maize fertilized with zinc (NPKZn) or magnesium (NPKMg) at the background of two nitrogen rates: 80 and 140 kg N·ha-1. The average maize grain yield (GY) over years amounted to 9.82 and 10.49 t·ha-1, for nitrogen rates 80 and 140 kg N·ha-1 respectively. Zinc or magnesium supply significantly influenced GY, however in treatments with 80 kg N·ha-1 [NPKZn (10.20 t·ha-1) ≥ NPKMg (9.89) > NPK (9.49)] only. In the treatment with 140 kg N·ha-1, yield increment due to zinc supply amounted to 0.36 t·ha-1. The multiple regression analysis with the choice of the best subset of independent variables (yield components) versus dependent variable (yield) revealed, that GY depended mainly on the thousand kernels weight (TKW), but in the NPK treatment, GY was a resultant of the interaction of all main yield components. TKW generally responded to N rate and Zn supply, but magnesium external supply is important to increase the seasonal yield stability. The results outline a possibility of significant nitrogen rate reduction provided external zinc and/or magnesium supply.
Key words: maize, fertilization, nitrogen efficiency, magnesium, zinc
Introduction
Maize is a crop of great economic values, both worldwide and in Poland, due to its versatile use [FAOSTAT 2005, Księżak 2008]. It is characterized by a high yielding potential, defined as a yield of plant variety grown under optimal conditions of water and nutrients supply under conditions of effective weed, pathogens and pests control [Evans and Fisher 1999]. Yielding potential of maize in Poland is in the range from 11 to 13 t·ha-1. However, grain yields actually harvested by farmers are much lower than the yield potential of current varieties, pursuant to unbalanced nutrition, among others [Grzebisz 2008].
The effect of externally supplied nutrients on yield formation is frequently referred to the application of nitrogen fertilizers and the evaluation of nutrient efficiency, beyond nitrogen, based mostly on phosphorus and potassium [Roberts 2008]. Long-term yield stability is a separate matter in the process of potential yield formation. The year-to-year yield variability results not only in the insufficient supply of nitrogen, but also due to the deficiency of secondary nutrients and micronutrients, especially on the light soils. In this context, care must be given by maize growers to magnesium and zinc in order to keep a proper nutritional balance in plant during the growth season [Grzebisz 2008, Lipiński 2005]. Data reported by [Atiken et al. 1999]
decidedly show, that magnesium fertilizer application significantly increased grain yield in magnesium-deficient Australian acid soils.
The improvement of mineral nitrogen efficiency after supplementing NPK fertilizers with magnesium has been reported by Rasheed et al. [2004]. These authors applying to the soil 15 kg Mg·ha-1 obtained maize grain yield increment by 1.1 t·ha-1 i.e. by 13%. Under tropical conditions, in a three year field trial with maize, zinc or magnesium applied as sulphate [Abunyewa and Mercer-Quarshie 2004] gained yield increments of 16.5% and 108%, respectively. The effect of zinc on maize grain yield was confirmed in many papers, where zinc has been applied as a foliar top-dressing [Leach and Hameleers 2001, Wrońska et al. 2007, Barłóg and Frąckowiak-Pawlak 2008, Potarzycki and Grzebisz 2009]. The predominance of NPK solid fertilizers in crop production induce to look for possibilities of enriching these fertilizers with magnesium and/or zinc in order to stimulate the yield forming effect of primary nutrients (N, P, K). In practice, NPK fertilizers considered as a carrier to zinc or magnesium can substantially decrease the cost of these nutrients applications.
Monoculture is frequently practiced in maize cropping. However, maize cropped in monoculture is sensitive to many biotic stresses, in turn leading to yield depression due to lower TGW [Kiężak 2010]. In addition, maize cropping system significantly affects N fertilizer efficiency, i.e. nitrogen recovery [Machul and Księżak 2007].
According to Nevens and Raheul (2001), fertilization is one of the factors limiting the negative impact of monoculture on maize yield, and this is related to some particular conditions, nitrogen application among others. Therefore, the hypothesis of zinc and magnesium stimulation in the control of nitrogen efficiency in the yield forming process may be formulated.
The aim of the paper was to assess effects of magnesium and zinc external supply using a solid NPK (as Mg and Zn carrier) on yield forming parameters of maize cultivated in monoculture against a background of two nitrogen rates.
Materials and methods
Field’s trials were carried out during five growth seasons from 2003 to 2007 at the agricultural farm located in Nowa Wieś Królewska (52.26o N; 17.57o E, Poland).
The long-term static trial was established on a loam soil formed from boulder clay.
All chemical analyses were performed according to methods reported by Lityński et al. [1976]. The soil, at the beginning of the experiment was characterized by a slightly acid pH, medium content of available potassium and magnesium and with organic carbon content amounting to 19.0 g·kg-1 (Table 1). Phosphorus content determined by the Egner-Riehm method varied from a medium to high. Among basic agrochemical characteristics the highest year-to-year fluctuation was found for available potassium. The yearly increment of potassium content, finally increasing by ca 10% over the period of five years has been recorded. Mineral nitrogen (N-NH4 + N-NO3) content in the soil layer (0-60 cm) was extracted by using the 0.01M CaCl2 test and further assayed by the FOSS autoanalyzer. Soil bulk density was involved in the calculation of mineral nitrogen content. Each year, the contents of soil mineral nitrogen, as assessed inspring, i.e., just before applying fertilizers, fluctuated within a narrow range, from 53 to 69 kg N·ha-1.
Table 1. Agrochemical properties of arable soil layer at spring before the application of fertilizer and maize sowing (layer 0.00 – 0.30 m)
Years Soil pH n 1mol·dm3
KCl
Organic carbon a
g·kg-1
Available phosphorus b
mg P·kg-1
Available potassium b
mg K·kg-1
Available magnesium c
mg Mg·kg-1
Available zinc d mg Zn·kg-1
Mineral nitrogen kg N ha-1 e
(layer 0-60 cm)
2003 5.8 19.0 57.2 116.2 50.0 6.0 59
2004 5.9 18.9 55.2 120.4 55.0 5.8 69
2005 5.7 19.2 61.0 120.4 52.5 6.1 63
2006 5.8 19.4 55.2 124.5 50.0 5.9 53
2007 5.6 19.2 61.0 128.7 47.5 6.1 68
a Tiurin method; b Egner-Riehm method; c Schachtschabel method; d 1M HCl; e 0.01M CaCl2
The rainfall distribution for the period of field trials as compared with the long- term (1960-2002) data are listed in Table 2. The highest year-to-year fluctuations in two critical months, i.e., in June and July from the long-term averages were in the years 2004 and 2006. The surplus of precipitation was only in 2007.
Table 2. Rainfalls for the years 2003-2007
Years
Total rainfall in the growth
season, mm
Deviation the long-from
term mean, %
Months - Deviation from the long-term mean, %
May June July August Septem-ber October
20032004 20052006 2007
181256 267357 427
- 46 - 23 - 20 + 7 + 28
- 44 - 58 +121+ 51 + 85
- 58- 24 - 55- 43 + 45
+ 8 - 53- 1 + 96- 90
+ 15- 75 - 2 + 227
+ 21
- 74- 51 - 50- 24 - 28
+ 63- 13 - 82+ 9 - 34 1the long-term mean = 305 mm
Maize, variety Eurostar (FAO 240), was cropped in monoculture in five consecutive years. A two-factorial field trial, replicated four times was established in a block system design with the following factors:
1. Nitrogen rate:
a. 80 kg N·ha-1 b. 140 kg N·ha-1
2. Chemical composition of the NPK fertilizer, based on super phosphate:
a. NPK with zinc, (NPKZn) + ammonium saltpeter;
b. NPK with magnesium, (NPKMg) + ammonium saltpeter;
c. NPK fertilizer (NPK) + ammonium saltpeter.
An experimental treatment without nitrogen (absolute control) was also included in four replications, irrespective of the basic experimental design. All treatments were provided annually with phosphorus and potassium, at 26.4 kg P·ha-1 and 99.6 kg K/ha, respectively. Treatments NPKZn and NPKMg received as soil inputs, 1.5 kg Zn·ha-1 (in the form of zinc sulphate) and 15 kg Mg/ha (in the form of magnesium carbonate). All nutrients were incorporated in one fertilizer granule.
This is a reason for not including the costs of separate broadcasting of zinc and magnesium to the total costs of fertilizer application. All fertilizers were applied just two weeks before maize sowing, in the third decade of April. The yield of grain was determined from an area of 24 m2 (two central rows of 16 m length) at technological maturity of grains (ca 70% dry weight basis). Total grain yields were adjusted to 14%
moisture content. At harvest each plant sample was partitioned into sub-samples of grain and straw (including leaves, stems, cob covering leaves and cob cores) and then dried (65oC). The following components of yield structure were estimated: thousand kernels weight (TKW), number of rows on the cob (NRC), number of kernels in the row (NKR), and number of kernels in the cob (NKC). A sample of 20 cobs for each treatment was used for determination the components of yield structure.
