Krzysztof Jankowski, Wojciech Budzyński, Andrzej Szymanowski University of Warmia and Mazury in Olsztyn
Department of Agrotechnology and Crop Management, Olsztyn, Poland
Influence of the rate and timing
of sulphur fertilisation on winter oilseed rape yield
Poziom i termin nawożenia siarką a plonowanie rzepaku ozimego
Key words: winter oilseed rape, sulphur fertilisation, wintering, seed yield, agronomic effectiveness This study presents the results of a three year (2000–2003) study investigating the influence of the timing (autumn + spring or only spring) and the rate of sulphur fertilisation (0, 30, 45, 60, 75, 90, 105, 120 kg·ha-1) on winter survival and yield of winter oilseed rape.
By exerting a beneficial effect on the weight and number of leaves and their survival in the rosette, a pre-sowing sulphur rate (ammonium sulphate) of 15 kg S·ha-1 supported the wintering of oilseed rape plants.
Sulphur fertilisation of 30 kg·ha-1, applied at a single rate in spring or at two rates – in the
pre-sowing period (15 kg S·ha-1) and in spring (15 kg S·ha-1), had a favourable influence on rape yield. The mean increase in seed yield reached around 300 kg·ha-1.
The net and marginal productivity of 1 kg S was the highest (11.3 kg seeds) at a rate of 30 kg S·ha-1. The applied measures of fertilisation effectiveness did not justify sulphur application at rates higher than 30 kg·ha-1.
Słowa kluczowe: rzepak ozimy, nawożenie siarką, przezimowanie, plon nasion, efektywność agronomiczna
W pracy przedstawiono trzyletnie (2000–2003) wyniki badań nad wpływem terminu aplikacji siarki (jesień + wiosna lub tylko wiosna) i poziomu dawki (0, 30, 45, 60, 75, 90, 105, 120 kg·ha-1) na zimowanie i plonowanie rzepaku ozimego.
Siarka (w siarczanie amonowym) aplikowana przedsiewnie w dawce 15 kg S·ha-1 wpływając korzystnie na masę i liczbę liści oraz ich utrzymanie się w rozecie powodowała pełniejsze zimowanie roślin rzepaku.
Korzystnie na plon wpływało nawożenie siarką w dawce 30 kg·ha-1, aplikowanej jednorazowo wiosną lub w podziale na dwie części — przedsiewną (15 kg S·ha-1) i wiosenną (15 kg S·ha-1). Średni przyrost plonu nasion wynosił ok. 300 kg·ha-1.
Produktywność netto oraz krańcowa 1 kg S była najkorzystniejsza (11,3 kg nasion) przy dawce 30 kg S·ha-1. Mierniki efektywności nawożenia nie uzasadniały aplikacji siarki w dawkach wyższych niż 30 kg·ha-1.
Introduction
The continued drop in sulphur deposition intensified the deficiency in the sulphur content of many crops, in particular plants of the family Brassicaceae, reducing their yield across many areas of Great Britain (McGrathand Zhao1995), northern Germany (Schnug et al. 1995a, Heneklauset al. 1995), France (Merrien and Maisonneuve1987), Denmark and southern Sweden (Schnug 1991). Sulphur emissions to ambient air have been falling steadily in Poland since the 1990s, from 51 (1990) to 21 kg S·ha-1 (2006) (Central Statistical Office 2008). Sulphur emissions are not evenly distributed throughout the country – in many less industrialised regions (including the Province of Warmia and Mazury), emission values do not exceed 10 kg S·ha-1 (Environmental Protection 2006).Exact experiments point to high sulphur productivity only in soils marked by a low sulphur content (Withers et al. 1995, Bilsborrow et al. 1995, Budzyński and Ojczyk 1995, Wielebski and Muśnicki 1998, Haneklaus et al. 1999 and Podleśna 2003). When fertilising rape with a sulphur rate of 40 or 50 kg S·ha-1, Withers et al. (1995) reported an increase in seed yield from 15 to 74%. In a study conducted by Bilsborrow et al. (1995), the highest (65% higher than control) yield results were noted in respect of rape grown in fields with a low sulphur content and fertilisation rate of 40 kg S·ha-1. A weak response to sulphur fertilisation was noted by Evans et al. (1991), Heneklaus et al. (1999), Wielebski and Muśnicki (1998), Budzyński and Ojczyk (1995) in plants with a high available content of sulphur.
The objective of this study was to determine the influence of the rate (0, 30, 45, 60, 75, 90, 105, 120 kg·ha-1) and timing of fertiliser application (autumn and/or spring) on the agronomic effectiveness of sulphur fertilisation of oilseed rape.
Materials and methods
This study was based on the results of an exact field experiment carried out in the experimental fields of the Research Station of the University of Warmia and Mazury in Bałcyny (N = 53º35`, E = 19º51`). The experiment was established in a randomized split-plot design, in 4 replications:factor I ⎯ sulphur rate (kg·ha-1
): (Ia) control; (Ib) 30; (Ic) 45; (Id) 60; (Ie) 75; (If) 90; (Ig) 105; (Ih) 120
factor II ⎯ time of sulphur application: (IIa) autumn (BBCH – 00) and spring (BBCH – 30), (IIb) spring (BBCH – 30)
BBCH – 00 0 15 30 30 30 30 30 30
IIa
BBCH – 30 0 15 15 30 45 60 75 90
The experiment was set on typical lessive silty soil developed from light loam, of quality class IIIa, a very good rye complex (2000 and 2001) or a good wheat complex (2002) (Table 1). Soil abundance in available phosphorus was evaluated as average to very high, in potassium – as average, in magnesium and sulphate sulphur — as low. Topsoil was acidic or slightly acidic (pH 5.3–5.9 in 1 M KCl). The rape forecrop were grain crops — spring barley (2000 and 2002) and winter wheat (2001). Experimental plot area was 18 m2.
A pre-sowing rate of 35 kg P·ha-1 in the form of triple superphosphate and 100 kg K·ha-1 in the form of highly concentrated potash salt were applied. The autumn pre-sowing nitrogen rate was 20 kg·ha-1. The spring nitrogen rate (160 kg·ha-1) was applied in two parts — 100 kg·ha-1 at stage BBCH 30 and 60 kg·ha-1 at stage BBCH 51. Nitrogen was applied in the form of ammonium nitrate (-S) or ammonium sulphate and ammonium nitrate (+S).
Table 1 Description of soil conditions ⎯ Charakterystyka warunków glebowych
Growing season ⎯ Sezon wegetacyjny Specification ⎯ Wyszczególnienie
2000/2001 2001/2002 2002/2003 Soil type ⎯ Typ gleby typical lessive soil ⎯ gleba płowa typowa Soil species ⎯ Gatunek gleby light loam ⎯ glina lekka
Soil pH ⎯ Odczyn gleby [1 M KCl] 5.3 5.9 5.9
Soil valuation class ⎯ Klasa bonitacyjna IIIa Soil suitability complex
Kompleks przydatności rolniczej
very good rye complex
żytni bardzo dobry
good wheat complex
pszenny dobry
Content of available nutrients [mg·kg-1 soil]
Zwartość przyswajalnych składników [mg·kg-1 gleby]
⎯ P 62.0 114.8 89.9
⎯ K 107.9 103.8 207.5
⎯ Mg 41.0 83.0 57.0
⎯ S-SO4 18.1 15.2 6.7
Dressed winter rape seeds cv. Lisek were sown between the 10th and 20th of August (2001, 2002) and in the last week of August (2000), at a density of 120 germinating seeds per m2 of plot area and spacing of 20 cm.
Dicotyledonous weeds were controlled with a post-sowing application of 999 g·ha-1 metazachlorine and 249 g·ha-1 of chinomerak, and monocotyledonous weeds — with 52 g·ha-1 of haloxyphop-R. Insecticides were applied after the level of insect infestation had exceeded the threshold determined by the Institute of Plant Protection in Poznań. During the spring growing season in the first and second year
of the experiment, a single treatment for the control of the rape blossom beetle was applied (300 g·ha-1 chloropiryphos + 30 g·ha-1 cypermetrine). During the third experimental cycle in the spring growing season, three treatments for the control of rape pests were applied (1 × cabbage curculio, 2 × rape blossom beetle) with the use of 7.5 g·ha-1 deltametrine, 7.5 g·ha-1 cypermetrine and 10 g·ha-1 alpha-cyper-metrine. Fungicides were not applied due to low infection intensity. Rape was harvested in a two-phase system at the beginning or end of the second week of July.
Growth stages were determined with the use of the BBCH scale – Biologische Bundesanstalt, Bundessortenamt und Chemical Industry (Muśnicki and Mrów-czyński 2006). Thousand seed weight was determined based on a seed sample from the entire plot (13% moisture content). Seed yield was calculated for the area of 1 ha and stated in terms of 7% moisture content (production raw material)
The results of plant biometric measurements and yield were verified by an analysis of variance in accordance with the experimental design. The mean values of the investigated traits in all treatments were compared with the use of Duncan's test. LSD values were stated for 5% error. Analyses of variance were performed with the use of STATISTICA® applications, and the remaining calculations were carried out in EXCEL® spreadsheet.
Results
Agrometeorological conditions
The autumn of 2000–2002 was a wet period. Total atmospheric precipitation from August to October exceeded the multi-annual precipitation average by 2 to 54%. The distribution of precipitation varied during the autumn growing season in particular years of the experiment.
In the first cycle of the study, intense rainfall was reported only in the pre-sowing period and at the beginning of germination (in August). In 2001, precipitation in excess of the average monthly levels was noted in August and September, and in 2002 — in all months of the autumn growing season (Fig. 1).
The winter dormancy period lasted from 153 to 172 days. Although according to multi-year statistics, January is the coldest month in the Ostróda Lakeland, the coldest month during the study was December (2001/2002, 2002/2003) and January in one of the experimental years (2000/2001). The lowest mean daily air temperature (up to minus 22ºC) was observed in December 2002. The mean daily air temperature for the entire winter dormancy period, including the period of the study, was the lowest in all investigated years (minus 2.2ºC). In the remaining years, the mean daily air temperature over the winter dormancy period ranged from minus 1.0ºC (2000/2001) to plus 1.4ºC (2001/2002) (Fig. 2).
0 20 40 60 80 100 120 140 160 2000 2001 2002 VIII IX X
Fig. 1. Moisture conditions during the autumn growing season — Układ warunków
wilgot-nościowych w okresie jesiennej wegetacji
The analysis of data presented in Figure 2 indicates that the drop in mean daily air temperature (below 5ºC) in the winter was always accompanied by snow cover which minimised the effect of low temperatures on plant wintering. During the cold winter of 2002/2003, plants were protected by snow cover with a depth of 5–10 cm.
The spring and summer growing seasons in 2001-2003 were marked by moderate precipitation which covered the water demand of winter oilseed rape. The highest precipitation was reported in the spring and summer season of 2000/2001 and 2002/2003. The monthly distribution of precipitation was highly diversified in the studied years. Insufficient precipitation to cover the water demand of plants was reported annually only in April (Fig. 3).
Atmospheric pre cipit ation [m m] O p ad y atmos fer yczne
-15.0 -10.0 -5.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 [ oC] , [ c m ]
Ten days - Dekady
November December January February March listopad grudzień styczeń luty marzec
0 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 2000/2001 -30,0 -20,0 -10,0 0,0 10,0 20,0 30,0 40,0 [ oC] , [ c m ]
Ten days - Dekady
0 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3
November December January February March listopad grudzień styczeń luty marzec
2001/2002 -25.0 -20.0 -15.0 -10.0 -5.0 0.0 5.0 10.0 15.0 20.0 25.0 [ oC] , [ c m ]
Ten days - Dekady
November December January February March listopad grudzień styczeń luty marzec
0 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3
2002/2003 snow depth — grubość pokrywy śnieżnej
mean daily air temperature — średniodobowa temperatura powietrza
Fig. 2. Mean daily air temperature [°C] and snow depth [mm] during the winter dormancy of plants — Średniodobowa temperatura powietrza [°C] oraz grubość pokrywy śnieżnej
0 20 40 60 80 100 120 2001 2002 2003
IV V VI VII (first 20 days - 1-2 dek.)
Fig. 3. Moisture conditions during the spring growing season — Układ warunków
wilgotnoś-ciowych w okresie wiosennej wegetacji
Growth and development of rape before winter dormancy.
Winter survival of rape plants.
On average, the habit of rape plants cv. Lisek before growth inhibition was evaluated as satisfactory over the three-year period (Table 2), with nearly nine leaves per rosette, adequate root neck diameter and satisfactory leaf weight.
The influence of pre-sowing sulphur on plant habit was clearly manifested, but it had a statistically significant impact only on selected attributes. A sulphur rate of 15 kg·ha-1 had a beneficial (significant) effect on the number of leaves and their survival in the rosette, and it decreased the rate of leaf shedding. Pre-sowing application of sulphur also had a noticeable (although statistically non-significant) influence on the fresh weight of the rosette and its dry matter accumulation (Table 2).
Table 2 Selected habit characteristics of rape plants in the pre-dormancy period, 2000–2003
Wybrane cechy przedspoczynkowego pokroju roślin rzepaku, 2000–2003
Pre-sowing S rate [kg·ha-1]
Przedsiewna dawka S
Plant habit characteristics
Cechy pokroju roślin
0 15 30
LSD
NIR
Number of leaves per rosette
Liczba liści w rozecie [szt.] 8.4 8.7 8.9 0.3
Root neck diameter [mm]
Średnica szyjki korzeniowej 6.2 6.0 6.3 n.s. ⎯ r.n.
Fresh weight of a rosette [g]
Świeża masa 1 rozety 17.0 18.0 18.7 n.s. ⎯ r.n.
Dry weight of a rosette [g]
Sucha masa 1 rozety 2.6 2.9 3.0 n.s. ⎯ r.n.
Atmospheric pre cipit ation [m m] Opady atmosfer yczne
During cold winters (first and third experimental cycle), sulphur had a beneficial effect on the winter survival of rape. In treatments fertilised with sulphur, the number of rape plants which survived the winter period increased by 5 and 10% in the first experimental cycle, and by 3 and 8% in the third experimental cycle, respectively, in comparison with the control treatment (no sulphur fertilisation). On average, the beneficial impact of sulphur fertilisation on the winter survival of rape plants in a three-year experimental period was evaluated as low (±2–5%), nevertheless a clear improvement trend was noted (Table 3).
Table 3 Winter survival of rape plants (%) ⎯ Przezimowanie rzepaku
Pre-sowing S rate [kg·ha-1]
Przedsiewna dawka S Growing season Sezon wegetacyjny 0 15 30 2000/2001 76.5 81.2 86.4 2001/2002 88.7 87.8 87.4 2002/2003 82.3 86.4 90.3 Mean ⎯ Średnio 82.5 85.1 88.0 LSD ⎯ NIR: n.s. ⎯ r.n.
Yield components
Stand density before harvest was adequate. In the first year, the mean number of rape plants reached 87 per m2, in the second and third year of the experiment – 55 and 51, respectively. The sulphur rate applied in the autumn did not exert a regular and beneficial impact on stand density. The observed number of yielding rape plants also indicates that the spring rate of sulphur fertilisation did not result in plant loss (due to phytotoxic activity or increased intrastand competition) (Table 4). The number of siliques per plant should be regarded as average (Table 4). It guaranteed more than 4000 siliques per m2 of stand area in the second and third year, and more than 5000 in the first experimental cycle. Except for the year factor, none of the experimental variables had a significant impact on this trait. A growing trend resulting from sulphur fertilisation was not reflected by the mean values for the investigated three-year period. Contrary to expectations, sulphur fertilisation in the spring did not improve fruit setting (Table 4). The product of the above two yield components, i.e. the number of siliques per m2 of stand area, was more favourable in treatments fertilised with sulphur than in plots where no sulphur fertilisation was applied. The observed trend was clearly manifested (Fig. 4).
The number of seeds per silique proved to be a varietal property which was not affected by sulphur fertilisation (Table 4).
Table 4 Yield components of winter oilseed rape (2000–2003) ⎯ Elementy struktury plonu
S rate [kg·ha-1] ⎯ Dawka S
Date of S application
Termin aplikacji siarki 0 30 45 60 75 90 105 120
Mean
Średnio
Number of yielding rape plants [m2] ⎯ Obsada roślin na 1 m2
BBCH 00 + BBCH 30 61 64 62 62 64 68 66 68 64
BBCH 30 61 65 70 62 65 65 65 62 64
Mean ⎯ Średnio 61 64 66 62 65 66 66 65
LSD ⎯ NIR: n.s. ⎯ r.n.
Number of siliques per plant ⎯ Liczba łuszczyn na roślinie [szt.]
BBCH 00 + BBCH 30 75 77 78 77 76 73 70 70 75
BBCH 30 75 72 64 74 70 73 74 74 72
Mean ⎯ Średnio 72 75 71 75 73 73 72 72
LSD ⎯ NIR: n.s. ⎯ r.n.
Number of seeds per silique ⎯ Liczba nasion w łuszczynie [szt.]
BBCH 00 + BBCH 30 24.6 24.8 25.6 25.1 24.4 24.7 25.2 25.0 24.9 BBCH 30 24.6 24.7 25.3 25.0 25.3 24.7 24.4 24.8 24.9 Mean ⎯ Średnio 24.6 24.7 25.4 25.1 24.8 24.7 24.8 24.9
LSD ⎯ NIR: n.s. ⎯ r.n.
Thousand seed weight [g] ⎯ Masa 1000 nasion
BBCH 00 + BBCH 30 5.20 5.20 5.23 5.25 5.08 5.20 5.17 5.16 5.19 BBCH 30 5.20 5.23 5.19 5.24 5.24 5.13 5.29 5.29 5.23 Mean ⎯ Średnio 5.20 5.21 5.21 5.25 5.16 5.17 5.23 5.22 LSD ⎯ NIR: n.s. ⎯ r.n. y = -14.47x2 + 157.2x + 4351 R² = 0.522 4100 4200 4300 4400 4500 4600 4700 4800 4900 0 30 45 60 75 90 105 120
Fig. 4. Correlation between S rate and the number of siliques per m2 — Związek pomiędzy
dawką siarki a liczbą łuszczyn na 1 m2 (2000–2003)
Number of siliq ues per 1 m 2 Liczba łuszczyn na 1 m 2
The collected rape seeds were characterised by high unit weight. Thousand seed weight increased as a result of sulphur application both in the autumn and spring as well as exclusively in the spring only in the first year of the experiment, when rape yield was high (Fig. 5). The above trend was not reported in the remaining growing seasons, which is why the mean results for 3 years are not diversified (Table 4). LSD ⎯ NIR: n.s. ⎯ r.n. 5,32 5,13 5,22 5,32 5,12 5,12 5,25 5,13 5,24 5,00 5,10 5,20 5,30 5,40 2000/2001 2001/2002 2002/2003 -S +S (A/S) +S (S)
Growing season — Sezon wegetacyjny -S — no sulphur fertilisation ⎯ bez nawożenia siarką
+S (A/S) — sulphur fertilisation in the autumn and spring ⎯ jesienne i wiosenne nawożenie siarką +S (S) — sulphur fertilisation in the spring ⎯ wiosenne nawożenie siarką
Fig. 5. Effect of sulphur application time on thousand seed weight — Wpływ terminu
nawożenia siarką na masę 1000 nasion
Seed yield
In the first experimental year, the seed yield of rape cv. Lisek was high at 5.82 Mg per ha. In the following years, rape seed yield per area unit decreased by 18% (2001/2002) and 13% (2002/2003). In every year, sulphur fertilisation had a continuously beneficial effect on seed yield weight per ha (Fig. 6).
Nevertheless, the differences between S rates were statistically non-significant or were not reported at all. The average increase in seed yield over the three-year experimental period reached approximately 300 kg·ha-1, and it was similar for all applied sulphur rates. Even though the productivity function takes on the form of a quadratic curve, it is largely flattened (Fig. 7). Yield increase did not vary subject to the time of fertiliser application into the soil. Therefore, the pre-sowing (autumn) and top-dressing (spring) rates as well as the rate applied entirely in the spring proved to be equally efficient (Fig. 6).
Thousand seed
weight
[g]
M
LSD ⎯ NIR: n.s. ⎯ r.n. 5,89 4,75 5,08 5,89 4,83 5,11 5,31 4,61 4,81 4,0 4,4 4,8 5,2 5,6 6,0 2000/2001 2001/2002 2002/2003 -S +S (A/S) +S (S)
Growing season — Sezon wegetacyjny -S — no sulphur fertilisation ⎯ bez nawożenia siarką
+S (A/S) — sulphur fertilisation in the autumn and spring ⎯ jesienne i wiosenne nawożenie siarką +S (S) — sulphur fertilisation in the spring ⎯ wiosenne nawożenie siarką
Fig. 6. Winter oilseed rape yield depending on sulphur fertilisation — Plonowanie rzepaku
ozimego w zależności od sposobu nawożenia siarką
y = -9E-05x2 + 0,0143x + 5,3777 R2 = 0,7214 y = -4E-05x2 + 0,0059x + 4,7436 R2 = 0,6035 4,5 4,7 4,9 5,1 5,3 5,5 5,7 5,9 6,1 6,3 0 15 30 45 60 75 90 105 120
S rate — Dawka S [kg·ha-1]
Fig. 7. Diagram of a function of sulphur fertilisation productivity — Wykres funkcji
pro-dukcji nawożenia siarką
S eed yi eld of wi nter o ils eed rap e [M g·ha -1 ] P lon nasion rz epaku o zimego S eed yi eld of wi nter o ils eed rap e [M g·ha -1 ] Plon nasion rzepaku ozimego 1st cycle 1. cykl 2nd and 3rd cycle 2. i 3. cykl
The net productivity of 1 kg S varied significantly over the experimental years. The best results were reported in the high yielding year (first experimental cycle), while the remaining two years were marked by significantly lower productivity (Fig. 8). y = -0,1382x + 19,816 R2 = 0,7085 y = -0,0606x + 8,4127 R2 = 0,7492 0,0 5,0 10,0 15,0 20,0 25,0 30 45 60 75 90 105 120
S rate — Dawka S [kg·ha-1]
Fig. 8. Net efficiency of 1 kg S [kg seeds] — Efektywność netto 1 kg S [kg nasion]
The net efficiency of 1 kg S was the highest at the S rate of 30 kg·ha-1, and according to the law of diminishing efficiency, it regularly decreased as fertiliser rates increased (Fig. 8). At the lowest S rate level, every kilogram of sulphur increased rape seed yield by more than 11 kg on average. At higher rate levels, the relevant increase was several-fold lower, and it did not justify the use of sulphur fertilisation (Table 5).
Table 5 Marginal productivity of 1 kg S [kg seeds] (2001–2003)
Produktywność krańcowa 1 kg S [kg nasion]
S rate [kg·ha-1] ⎯ Dawka S
30 45 60 75 90 105 120 11.3 0.7 0.3 ⎯ 1.7 1.0 ⎯ Net eff iciency of 1 kg S [kg seeds] Efe ktywno ść netto 1 kg S [kg nasion] 1st cycle 1. cykl 2nd and 3rd cycle 2. i 3. cykl
Discussion
The winter survival of winter rape plants is correlated with the habit of rosettes before growth inhibition. The contribution of various biometric properties to the phenological frost resistance of rape plants, interpreted by path analyses, indicates that the winter hardiness of rape plants is lowered mainly by the increased elevation of the growing point. A two-dimensional partitioning (TDP) analysis investigating the synthesis of the degree of rape plant wintering also shows that an increase in growing point elevation plays a key role in determining the winter hardiness of rape plants. Other habit characteristics of rape rosettes which play a less important, nonetheless statistically significant, role in winter survival are: the number of leaves formed in rosettes in the autumn, tap root length and dry matter yield per rosette (Jankowski 2007).In this study, sulphur fertilisation had a favourable effect on the weight and number of leaves per rosette, fresh weight of rosette and dry matter accumulation, thus increasing the winter survival rate of rape plants (by 3–10%). The beneficial impact of pre-sowing sulphur application on the wintering of rape plants was particularly visible during frosty winters.
The yield-forming effect of sulphur fertilisation is determined mostly by soil abundance in sulphur. Rape plants grown in soils rich in sulphur have a weak response to fertilisers based on this macronutrient, as demonstrated by the results of studies carried out by Budzyński and Ojczyk (1995), Wielebski and Muśnicki (1998), Evans et al. (1991), Bilsborrow et al. (1995), and Heneklaus et al. (1999). In soils marked by sulphur deficiency, sulphur fertilisation could increase the winter rape seed yield. In a study conducted by Podleśna (2004), the spring sulphur rate of 80–100 kg·ha-1 increased seed yield by 0.10–0.34 Mg·ha-1. Zukalová et al. (2001) reported a significant increase in seed yield (by 0.25 Mg·ha–1 in comparison with the control treatment) of up to 160 kg S·ha-1. In a study performed by McGrath and Zhao (1996), the spring sulphur rate increased seed yield by 0.12 Mg·ha-1, while Heneklaus et al. (1990) reported an almost 90% increase in basic yield. Krauze and Bowszys (2000) demonstrated that regardless of the manner of application (soil, foliar), spring sulphur fertilisation increased seed yield from 0.03 to 0.64 Mg·ha-1. The effectiveness of spring sulphur fertilisation was also high under production conditions — a higher sulphur supply resulted in a linear increase in seed yield (Jankowski et al. 2005).
According to Jankowski (2007), the yield-forming effect of sulphur fertilisation is linked to climatic and habitat conditions. The effectiveness of sulphur application was low in soils with a relatively high sulphur content (in sulphate form) and in years with average total precipitation during the autumn growing season. The yield-forming effect (an increase in seed yield by 0.27 Mg·ha-1) of
large sulphur rates (90 kg·ha-1) was clearly manifested in soils with a low SO4
content and in a year marked by intense precipitation in late autumn.
In this study, the autumn and spring application of sulphur (stage BBCH 00 and stage BBCH 30) produced the same yield-forming effect as the sulphur rates applied solely in the spring (stage BBCH 30). It should be noted that regardless of the rate and time of application, only sulphur rates not exceeding 30 kg·ha-1 had a beneficial impact on yield.
Large-area field experiments conducted by Jankowski et al. (2005) validated the high agronomic effectiveness of sulphur fertilisation. The gross productivity of 1 kg S reached around 12 kg of seeds for low rates (up to 30 kg·ha-1) and 4 kg of seeds for the highest rates (61–90 kg·ha-1).
In this study, the net productivity of 1 kg S was vastly differentiated throughout the experimental years — it was the highest in the year marked by the highest yield and significantly lower in the two remaining years. At the lowest sulphur rate (30 kg·ha-1), every kilogram of sulphur increased rape seed yield by more than 11 kg on average. A considerably lower increase was observed at higher rates, and it did not justify the application of sulphur fertilisation.
Conclusions
1. The pre-sowing application of sulphur (ammonium sulphate) at a rate of15-30 kg S·ha-1 had a beneficial effect on the weight and number of leaves and their survival in the rosette, thus supporting the winter survival of rape. 2. Sulphur fertilisation increased seed yield weight per ha. The average increase
in seed yield was approximately 300 kg·ha-1. Sulphur rates of 30 kg·ha-1, applied once in the spring or in two parts — in the pre-sowing period (15 kg S·ha-1) and in the spring (15 kg S·ha-1) — had the most beneficial effect on rape yield.
3. The net and marginal productivity of 1 kg S was the highest (11.3 kg seeds) at a fertilisation rate of 30 kg S·ha-1. The applied measures of fertilisation effectiveness did not justify sulphur application at rates higher than 30 kg·ha-1.
References
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