Leach, D.

Malhi, S.S.

English

University of Saskatchewan Research Archive

 Do we need to add more S fertilizer at high N rates for optimum canola yield, seed quality, and uptake of S and N?  S. S. Malhi1 and D. Leach1 1Agriculture and Agri-food Canada, Research Farm, Highway 6 South, P.O. Box 1240, Melfort, Saskatchewan, Canada S0E 1A0  BACKGROUND  • Crop requirements for S and N are closely linked because both are used for protein and chlorophyll synthesis in higher plant species.  • Canola has a high S requirement, which is greater than that of cereals, as canola has higher protein content and a higher proportion of the amino acids cysteine and methionine compared to cereals.  • On marginally S-deficient soils in the Parkland region, application of high rates of N and other fertilizers in combination with more frequent production of high yielding canola (Brassica napus L. or B. rapa L.) cultivars causes rapid depletion of S and nutrient imbalance in soil, and S deficiency and yield reduction in crops.  • Deficiency of S at any growth stage can cause considerable reduction in seed yield because S is immobile in plants. Therefore, a constant supply of available S to canola plants is thus needed throughout the growing season to prevent any seed yield loss due to S deficiency.  • Information on the optimum combination of fertilizer N and S rates on frequency and severity of S deficiency, and yield and quality of canola under field conditions in the Canadian prairies is needed.  OBJECTIVE • To determine the influence of fertilizer N and S rate combinations on yield, seed quality, and uptake of S and N for canola.   MATERIALS AND METHODS • Field experiments were conducted on four S-deficient Gray Luvisl (Boralfs) soils in northeastern Saskatchewan (Table 1).  • Precipitation during the experimental growing seasons was near normal.  • There were 16 fertilization treatments based on factorial combination of four rates of N (0, 50, 100 and 150 kg N ha-1) and four levels of S (0, 10, 20 and  30 kg S ha-1).  • The source of S was potassium sulphate (K2SO4) and of N was ammonium nitrate (NH4NO3).  • Each treatment was replicated four times in a randomized complete block design (RCBD).  • All fertilizers were broadcast on surface and incorporated into soil.  • Data were recorded on yield, total S concentration, S uptake, and N uptake of seed and straw, and protein and oil concentration of seed.   RESULTS • All four site-years showed similar trends for almost all parameters measured. The S x N interactions were significant for most parameters. So, the results on S x N interaction effects are presented as means of four site-years.      • In the absence of S application, increase in N rate made the S deficiency symptoms more severe, reduced yield, S concentration, oil concentration, S uptake and N uptake in seed, and generally tended to have no effect or some increase in yield, S uptake, and N uptake in straw up to 50 or 100 kg N ha-1 and reduced these at higher N rates.  • When S was applied, yield, S concentration, S uptake and N uptake in seed as well as the yield and S uptake in straw increased with increasing N rate; but maximum benefits were attained when S was applied at 20 kg S ha-1 and sometimes at 30 kg S ha-1.  • Irrespective of S rate, fertilizer N had no consistent effect on total S concentration, but reduced oil concentration and increased protein concentration in canola seed.  • With S fertilization, yield, S uptake and N uptake in seed and straw, and total S concentration and oil concentration in seed were substantially increased, whereas there was no consistent variation in protein concentration in seed.  • Response of these parameters to S application was generally greater at higher N rates. Sulphur and N uptake measured in both seed and straw indicated that significant N x S interaction effects were more frequent and pronounced for seed yield than for straw yield, indicating that response to N rate was relatively more dependent on the S level for seed than for straw.   CONCLUSIONS  • The use of S fertilizer was critical to avoid negative effects from N fertilization on canola, and to obtain a positive response of canola from N fertilization in S-deficient soil conditions, especially on yield, S concentration, oil concentration and S uptake of seed. • In the absence of S fertilizer, application of N alone reduced canola yield, S concentration, oil concentration, and S and N uptake in seed drastically.  • As S application alone increased yield, S concentration, oil concentration, protein concentration, S and N uptake of seed, and yield and N uptake of straw, it was clearly the nutrient more limiting than N at these sites.  • The relative response of canola to S application was generally greater at high N rates.  • When yield, and S and N uptake were measured in both seed and straw, the response of canola to increasing N rate was more dependent on the S level for seed than for straw.  • Overall, the results indicate an increased requirement for S application when a high rate of N is applied to attain optimum canola yield and seed quality.  ACKNOWLEDGEMENTS • The authors thank D. Leach, K. Fidyk and K. Hemstad-Falk for technical help.    Table 1. Some characteristics of soils for the different site-years in northeastern Saskatchewan  Site-year Great GroupZ Depth  (cm)  Texture Organic matter (%) pH (1:2 water) SO4-S (mg kg-1) NO3-N (mg kg-1) Tisdale 1999 Gray Luvisol 0-15 Sandy loam 4.6 6.5 10.0 5.6   15-30   7.2 10.0 4.8   30-60   7.2 8.0 3.6 Porcupine Plain 1999 Gray Luvisol 0-15 Loam 3.2 7.1 7.4 6.6   15-30   7.8 7.4 3.2   30-60   8.4 6.8 2.8 Tisdale 2000 Gray Luvisol 0-15 Sandy loam 4.6 6.7 7.4 6.2   15-30   7.0 6.2 2.6   30-60   7.3 4.8 2.0 Archerwill 2000 Gray Luvisol 0-15 Sandy loam 5.4 7.7 7.8 8.0   15-30   7.8 6.0 5.8 Z Based on Canadian Soil Classification System.      Figure 1. Seed and straw yield of canola at different N rates as influenced by S rate, averaged for the four site-years in northeastern Saskatchewan  0200400600800100012001400160018000 50 100 150Seed yield (kg ha-1)  0 kg S ha -1   y =  0.015x 2  - 5.01x + 464      R 2 = 0.999 **10 kg S ha -1   y = -0.044x 2  + 7.36x + 615      R 2 = 0.995 **20 kg S ha -1   y = -0.023x 2  + 7.65x + 654      R 2 = 0.999 **30 kg S ha -1   y = -0.033x 2  + 9.35x + 661      R 2 = 0.996 **_                   0 kg S ha -1           _                        10 kg S ha -1 _                  2 0 kg S ha -1           O                     30 kg S ha -1 1aRate N (kg N ha -1 )Seed yield (kg ha-1)0500100015002000250030003500400045005000550060000 50 100 150Straw yield (kg ha-1)  0  kg S ha -1    y  = -0 .085x 2  + 17.7x + 1888      R 2  = 0.999 **10 kg S ha -1    y  = -0 .178x 2 + 47.0x + 2284      R 2  = 0.968 *20 kg S ha -1   y  = -0 .183x 2 + 50.1x + 2049      R 2 = 0.989 **30 kg S ha -1    y  = -0 .083x 2 + 34.0x + 2217      R 2  = 0.992 *Rate N (kg N ha -1 )1bStraw yield (kg ha-1)  Figure 2. Oil content, protein content and concentration of S in seed of canola at different N rates as influenced by S rate, averaged for the four site-years in northeastern Saskatchewan.    Figure 3. Uptake of S in seed, straw and seed+straw of canola at different N rates as influenced by S rate, averaged for the four site-years in northeastern Saskatchewan.     3003203403603804004204404604805000 50 100 150Oil concentration in seed (g kg-1)  0 kg S ha -1   y =   0.0045x 2  - 1.139x + 433     R 2  = 0.999**10 kg S ha -1  y = - 0.0020x 2  - 0.030x + 444     R 2  = 0.995**20 kg S ha -1   y = - 0.0008x 2 - 0.105x + 446     R 2 = 0.876 ns30 kg S ha -1   y = - 0.0006x 2 - 0.073x + 446     R 2 = 0.946*_                     0 kg S ha-1           _                        10 kg S ha-1 _                    2 0 kg S ha-1           O                      30 kg S ha-1 1601701801902002102202302400 50 100 150Protein concentration in seed (g kg-1)   0 kg S ha -1  y = -0.0018x 2 + 0.461x + 189    R 2 = 0.994**10 kg S ha -1  y =  0.0012x 2 + 0.034x + 193    R 2 = 0.997**20 kg S ha -1  y =  0.0010x 2 + 0.022x + 197    R 2 = 0.962*30 kg S ha -1  y =  0.0012x 2 + 0.026x + 193    R 2 = 0.996**500100015002000250030003500400045000 50 100 150Concentration of S in seed (mg kg-1)  0 kg S ha -1  y =   0.027x 2  -  5.494x + 2465     R 2  = 0.965*10 kg S ha -1  y =                  -  3.875x + 3125    R 2  = 0.996**20 kg S ha -1  y =                  + 0.050x + 3290    R 2 = 0.015 ns30 kg S ha -1  y =   0.009x 2  + 1.406x + 3292      R 2  = 0.988**2a2b 2cRate of N (kg N ha - 1) Rate of N (kg N ha - 1)Rate of N (kg N ha - 1 )Oil concentration in seed (g kg-1)Protein concentration in seed (g kg-1)Concentration of S in seed (mg kg-1)012345670 50 100 150Uptake of S in seed (kg ha-1)  0 k g  S  h a -1   y =   0.00003x 2  -  0.011x + 1.07      R 2  = 0.999**10 k g  S  h a -1   y = -   0.0001x 2  + 0.018x + 1.76      R 2  = 0.960*20 k g  S  h a -1   y = - 0.00007x 2  + 0.023x + 1.96      R 2 = 0.995**30 k g  S  h a -1   y = -   0.0001x 2  + 0.031x + 1.98      R 2 = 0.991**_                   0 kg S ha -1            _                        10 kg S ha -1 _                  2 0 kg S ha -1            O                      30 kg S ha -1 024681012140 50 100 150Uptake of S in straw (kg ha-1)  0 k g  S  h a -1   y = -0.00008x 2  + 0.012x + 2.50      R 2  = 0.936*10 k g  S  h a -1   y = -  0.0002x 2  + 0.043x + 4.66      R 2  = 0.369 ns20 k g  S  h a -1   y = -  0.0004x 2  + 0.079x + 5.57      R 2  = 0.990**30 k g  S  h a -1   y = -  0.0006x 2  + 0.122x + 6.01      R 2  = 0.995**Rate of N (kg N ha -1 ) Rate of N (kg N ha -1 )3a 3b   Figure 4. Uptake of N in seed, straw and seed+straw of canola at different N rates as influenced by S rate, average for the four site-years in northeastern Saskatchewan.    051 01 52 02 53 03 54 04 55 05 56 00 5 0 1 0 0 1 5 0Uptake of N in seed (kg ha-1)  0  k g  S  h a -1   y  =    0 .0 0 0 3 x 2  - 0 .1 2 x  +  1 3 .6     R 2  =  0 .9 9 7 **1 0  k g  S  h a -1   y  =  -0 .0 0 1 2 x 2  +  0 .2 2 x  +  1 8 .3     R 2  =  0 .9 9 8 **2 0  k g  S  h a -1   y  =  -0 .0 0 0 4 x 2  +  0 .2 3 x  +  1 9 .8     R 2  =  0 .9 9 6 **3 0  k g  S  h a -1   y  =  -0 .0 0 0 8 x 2  +  0 .2 8 x  +  1 9 .6     R 2  =  0 .9 9 5 **_                   0 kg S ha -1           _                         10 kg S ha -1 _                  2 0 kg S ha -1           O                       30 kg S ha -1 051 01 52 02 53 03 54 04 55 05 56 00 5 0 1 0 0 1 5 0Uptake of N in straw (kg ha-1)  0  k g  S  h a -1   y  =  -  0 .0 0 0 6 x 2  +  0 .2 2 x  +  1 3 .3       R 2  =  0 .9 9 9 **1 0  k g  S  h a -1   y  =  -  0 .0 0 1 0 x 2  +  0 .3 9 x  +  1 5 .3       R 2  =  0 .9 9 8 **2 0  k g  S  h a -1   y  =  -  0 .0 0 0 8 x 2  +  0 .3 6 x  +  1 6 .9       R 2  =  0 .9 9 3 **3 0  k g  S  h a -1   y  =   0 .0 0 0 0 3 x 2  +  0 .2 3 x  +  1 6 .4       R 2  =  0 .9 9 8 **Rate of N (kg N ha -1 ) Rate of N (kg N ha - 1)4a 4b

Do we need to add more S fertilizer at high N rates for optimum canola yield, seed quality, and uptake of S and N?

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Do we need to add more S fertilizer at high N rates for optimum canola yield, seed quality, and uptake of S and N?

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