Vlastimil Mikšík, Jan Vašák
Czech University of Agriculture, Praha Suchdol
Influence of pre-seeding treatment with nitrogen
and N
minsoil content on accumulation
of biomass in rapeseed plants in autumn
Wpływ przedsiewnego traktowania azotem i zawartości N
minw glebie na gromadzenie biomasy w roślinach rzepaku na jesieni
Key words: rapeseed, pre-seeding, nitrogen fertilization, autumn, nitrogen uptake, dry matter, biomass accumulation
Słowa kluczowe: rzepak, nawożenie przedsiewne, azot jesienią, pobieranie azotu, akumulacja suchej biomasy
Przedsiewne nawożenie 20 kg N/ha powodowało zwiększenie przyrostów biomasy nadziemnej. Jeżeli sezon jesienny był wystarczająco długi następowała również akomodacja składników mineralnych i biomasy korzeni. Nawożenie przedsiewne azotem zwiększa istotnie zawartość N min w glebie i przyspiesza rozkład związków organicznych. Korzenie przyrastają głównie od listopada, gdy niskie temperatury powodują zahamowanie przyrostów biomasy nadziemnej. Przed nadejściem zimy materia organiczna przemieszcza się z masy nadziemnej do korzeni, co powoduje wzrost suchej masy w korzeniach. Ma to pozytywny wpływ na przezimowanie.
Pre-seeding treatment 20 kg per ha of nitrogen increases the growth of above-ground biomass of winter rapeseed. It supports nutrient accumulation and root biomass, if autumn season is long enough. Otherwise it supports the growth of above-ground biomass mainly. Pre-seeding treatment with nitrogen increases statistically significantly the content of Nmin in
soil and increases the decomposition of organic matter. Roots grow mainly since November when the effect of temperatures aborts the growth of above-ground biomass. Before the entrance of winter organic matter in plant accumulates from the above-ground to roots and content of dry matter increases in roots. Thus it positively influences over-wintering.
Introduction
In the last years there exists a European shift in the views on the need and effectiveness of the autumn or pre-sowing N fertilization of winter rape. The nitrate washing up in a higher quantity is one of the main reasons for this statement. Other reasons are in uncertain over-wintering and a high price of nitrogen fertilizers (Mikšík 1996).The winter rape-seed autumn fertilization depends on the availability of soil nitrogen (Holmes i Ainsley 1978, La Taille 1980) and also on the soil fertility, level of N nitrification, previous crop (Lesage 1976).
The results from Great Britain show the suitability of pre-sowing N fertilization (MAFF 1988; in Chalmers i Darby 1992). According to Holmes i Ainsley (1978) economically most efficient for high yields is the pre-sowing rate 60 kg N/ha. But these results were not significant in other parts of Europe (Gisiger 1956, Pieczka 1969, Goralski 1970, Debowski 1971, in: Holmes i Ainsley 1978, Sieling 1992, Mikšík 1996).
The higher plant growth in the autumn season fertilized by N need not to increase the yield (Ogilvy 1985, Chalmers 1989, Chalmers i Darby 1992, Chalmers i Froment 1992), but the standard pre-sowing doses 50 kg N/ha have been recommended in England and Scotland for many years.
The newer papers in Great Britain indirectly show a little or none influence of the autumn N fertilization (post-sowing or pre-sowing) on the winter rape yield (Ogilvy 1985, Chalmers 1989, Chalmers i Darby 1992, Chalmers i Froment 1992).
Material and methods
Small plots fertilizing experiments were founded at the Research Station of the Faculty of Agronomy in Červený Újezd in 1994/95. This Station is situated approximately 22 km from Prague at the border of the districts Kladno and Prague-West.The locality lies in a mild temperature area, mild dry climatic region mostly with mild winter seasons.
The mean annual temperature is 7.7oC; mean annual precipitation sum
– 493 mm. The length of vegetation period is 150–160 days. The first frosts come about 11. October.
The area of interest was created by clay states of chalk age formation, over-covered by eolian soils. The eolian soils are the main soil substrates creating grey-brown podzolic soil, less luvic grey-brown soil, chernozem-grey grey-brown. The soils were medium heavy textured with the topsoil which is from 25 to 30 cm deep. The volume mass was 1.4 t/m2 (according to Matula 1994), 7% of skeleton.
The soil has medium — high sorption capacity and neutral reaction. The humus content — medium. P and K contents medium — good. Mean N content after sowing was 28 ppm (previous crop — spring wheat), before the winter season 20 ppm and before spring season 25 ppm.
The experiments were established on the field with 5 year crop rotation. One – year fertilizing experiments in the rotation winter rape — pea — winter wheat — sugar beet (with manure) — spring or winter wheat — were established.
The experiment had 8–12 replicates. The peas area was 10 m2. The experimental variants are given in the Table.
Variant — Wariant No. replicates — Liczba powtórzeń
Without N fertilization — Bez nawożenia azotem 12 Fertilized — Nawożenie 20 kg N/ha (29.8.1994) 8
Plant sampling for N
totaldetermination
• After sampling of whole plants from 0.5 m row (by a spade) were:
— determination of plant numbers — the roots washed by lukewarm water — the plants splitted at the line of root neck
— weight from 0.125 m2 in each replicate determined: fresh above-ground biomass
fresh root mass
— the plant material was dried immediately in a drying box at 95oC with pre-drying treatment at 105oC
— after drying the weight of individual sample parts were determined: above-ground biomass (dry matter)
root mass (dry matter)
• The samples were crushed and preserved in paper bags.
The determination of total N was made the Kjeldalization at 420oC, on
KJELTEC apparatus AUTO 1030 ANALYZER at the Department of Agrochemistry and Plant Nutrition, FA CUA.
Soil sampling for N
mindetermination
The soil sample was taken by the probing rod (min. 16 stabs for 4 replicates) from the plant sampling place, before sampling. The sum sample from all the replicates in each variant was analysed. The Nmin content was determined from the fresh soil in Č. Újezd by means of modified distillation method according to Bremner & Keeney.
Results and discussion
Biomass accumulation and the source of Nmin content depending on N fertilization is given in Table 3 and Graf 1.0 5 10 15 20 25 30 35 40 45 50
Accum. roots biom. (g/m2), Nmin (ppm) 0
20 40 60 80 100 120 140
Accum. of DM in above-gr. biom. (g/m2)
21 23 26
phase (DC)
0 N - Nmin content (ppm) 20 N - Nmin content (ppm) 0 N - accum. biomas in roots 20 N - accum. biom. in roots 0 N - accum. above-ground biomass 20 N - accum. above-ground. biom.
Date of sampling (phase DC) 21 DC = 21.9. 23 DC = 19.10. 26 DC = 6.12. N fertilize: 29.8.1994 49 days 97 days Days count from sowing = 21
Graf 1. Accumulation of root and above-ground biomass dry matter and the development of Nmin
content, Červený Újezd, autumn 1994 — Akumulacja suchej biomasy w korzeniach i w masie
nadziemnej i tworzenie się azotu mineralnego Červený Újezd, autumn 1994
The above-ground biomass grew mainly from the period of emergence till the first half of October. Roots strengthened mainly from November, needed higher temperatures for the above-ground biomass growth.
The more intensive growth of roots depends also on plant hardening. At low night temperatures more intensive transportation of nutrients from the above-ground biomass into roots takes place. The plants start to prepare for over-wintering. It is therefore very important to foresee the longest autumn period and the slow beginning of cold night temperatures at the end of November or in December.
The root dry matter accumulation and above-ground biomass was higher on fertile soils in Č. Újezd in the fertilized variants. The accumulation was much higher especially in the root system in comparison with the variants without fertilization. At the end of autumn the biomass accumulation can be 50% higher in the fertilized variant.
The course of Nmin content is typical, and is corresponding to each year development. During the soil preparation for rape-seed sowing a top-soil aeration is present. The mineralisation of organic matter is then more intensive and it is forced by getting the harvest rests of the previous crops into the soil. The decrease of Nmin contents is caused by its uptake by plants or gradual washing off. The difference of Nmin between the fertilized and non-fertilized variant is usually relatively high, and for the N fertilization can cause a higher intensity of organic matter mineralization (so called priming effect).
The dry matter and N content in root biomass and above-ground matter depending on N fertilization is given in Table 2 and following Diagrams.
10 12 14 16 18 20 22 D ry m a tte r co n te n t in ro o ts (%) 3 3,2 3,4 3,6 3,8 4 4,2 4,4 4,6 4,8 5 Nt ot al c ont ent i n r oot s ( % ) 21 23 26 phase (DC)
0 N - dry matter content 20 N - dry matter content 0 N - Ntotal content 20 N - Ntotal content
Date of sampling (phase DC) 21 DC = 21.9. 23 DC = 19.10. 26 DC = 6.12. N fertilize: 29.8.1994
Diagram 2. Dry matter content in roots (%) and Ntotal content in roots (%). Červený Újezd, autumn
1994 — Zawartość suchej masy i azotu Ntotal w korzeniu
10 11 12 13 14 15 16 17 18 19 20 21 22 Dry mat te r c ont ent in abov e-ground (% ) 3 3,2 3,4 3,6 3,8 4 4,2 4,4 4,6 4,8 5 Nt ot al c ont ent in abov e-ground (% ) 21 23 26 phase (DC)
0 N - dry matter content 20 N - dry matter content 0 N - Ntotal content 20 N - Ntotal content
Date of sampling (phase DC) 21 DC = 21.9. 23 DC = 19.10. 26 DC = 6.12. N fertilize: 29.8.1994
Diagram 3. Dry matter content in above-ground biomass (%) and Ntotal content in above-ground
Ntotal in roots and above-ground biomass are different in their development as well as in the dry matter content.
The N concentration in above-ground biomass is very high from the winter rape plants emergence (Ntotal = till 5%). Gradually – with the rape-seed growth the N content is growing lower in connection with the nutrient dilution.
The N root content stagnates from the plant emergence and is increasing during the plant hardening. The reutilization of nutrients from the above-ground matter is evident during the hardening process, because the accumulated high – energetic compounds, the soluble sugar included, are transferred to the root neck and growing point (the first phase of hardening according to Golcov at all, 1983). At the same time the superfluous water flows away from the cells (the second phase of hardening according to Golcov at all, 1983) and N content and plant winter resistance increases with the higher cell sap concentration.
The N content is higher at the beginning in the fertilized variants, but at the end of autumn vegetation the interdependence between 2 variants changes due to strong biomass growth – mainly at the fertilized roots (diluting nutrient effect).
The root dry matter increased gradually since the time of emergence. It stagnates before the beginning of winter season and it shows the readiness of the stand for the winter time. The roots over-winter better if the dry matter and the cell sap concentration is higher. The difference between the fertilized and non-fertilized variant was in minimum to a N fertilized variant disadvantage.
The dry matter content at the above-ground matter development is different. The highest dry matter content comes in the middle of autumn vegetation, when the rape-seed nutrient uptake is very intensive. Before the start of winter season the above-ground matter water content is relatively high, probably due to a nutrient transfer to the roots. Therefore the plants lose at first the older leaves, keeping much water and their nutrients are transferred to the younger leaves or roots.
Statistical evaluation
The pre-sowing N fertilization shows up significantly (α = 0,01) in the winter rape roots, which are growing slower at the beginning, in the third sampling, i.e. at the end of vegetation. It means that the fertilization is positive in the root biomass accumulation only, when the autumn growth period is long enough, i.e. the coming of low temperatures is at the end of November or the beginning of December.
The same situation occurs at the above-ground biomass (α = 0,01). The above-ground biomass dry matter is faster from the start in comparison with roots.
N uptake in roots and above-ground matter in individual terms is similar to dry matter accumulation (α = 0,01). Almost one month after an application (the first soil sampling — 21.9.1994, pre-sowing N application — 29.8.) the Nmin was significantly higher (α = 0,01) in the fertilized variant.
w korzeniach i masie nadziemnej Sampling
[kg N (date)]
n
o
p
q
r
s
t
u
v
unfertilized check variant (n = 12) — wariant kontrolny, bez nawożenia
0 — 21.9.94 0,199 A 0,017 A 4,2 A 0,58 A 26,97 C 4,75 C 3,02 A 12,04 A 13,64 A
0 — 19.10.94 1,453 BC 0,187 A 37,67 BC 6,06 A 16,03 AB 3,88 B 3,1 AB 17,60 C 20,80 B
0 — 06.12.94 3,724 D 1,104 B 94,52 D 31,33 B 12,1 A 3,93 B 3,53 D 14,28 B 21,54 B
fertilized 20 kg N/ha (n = 8) — nawożenie 20 kg N/ha
20 — 21.9.94 0,261 AB 0,0215 A 5,27 AB 0,65 A 48,25 D 4,96 D 3,3 C 12,04 A 12,98 A 20 — 19.10.94 2,381 CD 0,283 A 59,7 CD 8,75 A 20,2 B 3,98 B 3,24 BC 17,70 C 20,33 B 20 — 06.12.94 5,209 E 1,676 C 141,44 E 49,55 C 13,4 A 3,69 A 3,4 CD 14,85 B 21,32 B F-test P value (α) 53,31 0,000 67,99 0,000 56,52 0,000 62,17 0,000 146,58 0,000 231,79 0,000 37,72 0,000 222,56 0,000 199,87 0,000
Note: Mean value are described as (A, B, C, D), where the means are identified by different letters giving significant difference at α=0,01
according to the Bonferroni’s method (P= 99%, n= 8 a 12) — A, B, C, D oznaczają istotne różnice przy α=0,01 wg metody Bonferroni
n = uptake N in above-ground parts — pobieranie azotu [g/m2
]
o = uptake N in roots — pobieranie azotu w korzeniach [g/m2
]
p = accumulation of dry matter in above-ground parts — akumulacja suchej masy w części nadziemnej [g/m2
]
q = accumulation of dry matter in roots — akumulacja suchej masy w korzeniach [g/m2
] r = Nmin content in soil — zawartość azotu w glebie [ppm]
s = Ntotal content in above-ground parts — zawartość azotu w części nadziemnej [%]
t = Ntotal content in roots — zawartość azotu w korzeniach [%]
u = dry matter content in above-ground parts — zawartość suchej masy w części nadziemnej [%] v = dry matter content in roots — zawartość suchej masy w korzeniach [%]
Table 2 Accumulation of dry matter in roots and in above-ground parts depending on N fertilization (autumn 1994, Č. Újezd)
Accum. biomass in roots (g/plant.) Accum. biomass in roots (g/m2) Accum. above-ground mass (g/rostl.) Accum. above-ground mass (g/m2) Ntotal content (%) Dry matter content (%) Nmin content in soil (ppm) Variants Phase No. of plants per m2 fresh mass dry matter fresh mass dry matter fresh mass dry matter fresh mass dry matter roots above-ground roots above-ground NNH4 + NNO 3– sum First 21.9.94 1. kontrola 21 DC 56 0,05 0,01 2,6 0,4 0,39 0,05 22 2,8 3,23 4,82 15,29 12,76 9,7 16,1 25,8 2. kontrola 21 DC 94 0,06 0,01 6 0,8 0,49 0,06 45,8 5,3 2,91 4,72 13,71 11,46 11,8 16,4 28,2 3. kontrola 21 DC 74 0,06 0,01 4,5 0,5 0,52 0,06 38,2 4,5 2,93 4,7 11,92 11,9 10,6 16,3 26,9
AVG of unfertilised variants 74,67 0,06 0,01 4,37 0,57 0,47 0,06 35,33 4,20 3,02 4,75 13,64 12,04 10,70 16,27 26,97
30 kg N 21 DC 84 0,06 0,01 4,7 0,6 0,5 0,06 41,9 5,3 3,3 4,9 13,7 12,68 19 35,5 54,5 20 kg N 21 DC 76 0,07 0,01 5,4 0,7 0,6 0,07 45,8 5,2 3,3 5,01 12,24 11,4 13,6 28,4 42
AVG of fertilised variants 80,00 0,07 0,01 5,05 0,65 0,55 0,07 43,85 5,25 3,30 4,96 12,97 12,04 16,30 31,95 48,25
Secont 19.10.94
1. kontrola 23 DC 40 0,56 0,12 22,4 4,9 4,68 0,83 187,1 33 3,26 4,06 21,82 17,66 8,6 8,3 16,9 2. kontrola 23 DC 82 0,54 0,11 44,5 8,7 3,61 0,63 296 51,5 3,03 3,72 19,58 17,41 6,2 8,1 14,3 3. kontrola 23 DC 60 0,36 0,08 21,8 4,6 2,67 0,47 160,4 28,4 3,01 3,87 21,01 17,71 6,6 10,3 16,9
AVG of unfertilised variants 60,67 0,49 0,10 29,57 6,07 3,65 0,64 214,50 37,63 3,10 3,88 20,80 17,59 7,13 8,90 16,03
30 kg N 23 DC 62 0,55 0,11 33,9 6,8 4,42 0,8 274 49,7 3,26 3,9 20,12 18,15 7,7 17,7 25,4 20 kg N 23 DC 64 0,81 0,17 52 10,7 6,31 1,09 404 69,7 3,21 4,05 20,55 17,25 7,9 7,1 15
AVG of fertilised variants 63,00 0,68 0,14 42,95 8,75 5,37 0,95 339,00 59,70 3,24 3,98 20,34 17,70 7,80 12,40 20,20
Third 6.12.94
1. kontrola 26 DC 54 2,06 0,43 111,5 23,4 10,38 1,53 560,5 82,4 3,59 4,04 21,03 14,7 3,5 9,6 13,1 2. kontrola 26 DC 70 2,55 0,55 178,3 38,6 11,37 1,69 796,2 118,6 3,53 4,01 21,65 14,9 2,2 8,2 10,4 3. kontrola 26 DC 70 2,08 0,46 145,5 32 8,91 1,18 623,7 82,5 3,47 3,74 21,96 13,23 2,4 10,4 12,8
AVG of unfertilised variants 64,67 2,23 0,48 145,10 31,33 10,22 1,47 660,13 94,50 3,53 3,93 21,55 14,28 2,70 9,40 12,10
30 kg N 26 DC 76 2,73 0,57 207,7 43 11,21 1,68 851,7 127,6 3,53 3,76 20,68 14,98 3,6 11,2 14,8 20 kg N 26 DC 78 3,28 0,72 255,6 56,1 13,52 1,99 1054,4 155,3 3,27 3,62 21,96 14,73 3,4 8,6 12
AVG of fertilised variants 77,00 3,01 0,65 231,65 49,55 12,37 1,84 953,05 141,45 3,40 3,69 21,32 14,86 3,50 9,90 13,40
Higher content of Nmin in soil has a positive influence on N uptake and finally on the dry matter accumulation in the root and above-ground matter. This relationship is statistically evident (α = 0.01) at the end of autumn growth vegetation (see the third sampling).
The relationship between Nmin mainly at the start of vegetation period and the N uptake (or the biomass accumulation — dry matter or fresh biomass of the plant) in the later period is directly proportional. But the significance of N fertilization
in autumn and spring period is not much evident in natural fertile soils in Č. Újezd due to the high Nmin content in the soil in the autumn season (mean
28 ppm) and in the spring (mean 23 ppm). The limit for the pre-sowing N dose
is 10 ppm and less Nmin (Neuberg at al, 1990).
The Ntotal content in roots and above-ground parts is in the fertilized variants significantly higher at the beginning of the vegetation (α = 0.01), due to the increased N uptake by roots in case of a higher Nmin content in the soil.
In non-fertilized variant the total N content in roots reaches its highest point at the end of autumn vegetation, but in comparison with the fertilized variant, to the detriment of significantly lower dry matter accumulation and significantly lower N uptake by roots (α = 0.01).
The total and content in above-ground biomass at the end of autumn vegetation is strongly decreasing, probably due to its root system utilization.
No statistically significant difference appeared in the root dry matter and above-ground biomass between the fertilized and non-fertilized variants. The root dry matter content is strongly increasing at the end of vegetation and so becomes one of the mean presumption of successful over-wintering. In the above-ground mass the dry matter content decreases due to the gradual extinction of other leaves and the nutrient transfer to the younger leaves and roots.
Recommendation
• N fertilization in the autumn season is suitable at the Nmin content before
sowing, lower than 10 ppm.
• The influence of N fertilization in the autumn period, or before sowing on the
dry matter increase is positive only if the autumn growth period is long enough. However, it has a negative effect – it supports the above-ground biomass growth to the detriment of winter rape roots.
• The effect of N pre-sowing fertilization did not show any positive effects on
References
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