Beaton, J.D.

Campbell, C.A.

Nicholaichuk, W.

Parker, G.E.

Zentner, R.P.

English

eCommons@USASK

Interaction of snow management × N & P fertilizer and their effect on spring wheat yields

University of Saskatchewan Research Archive

. - 63 -INTERACTION OF SNOW MANAGEMENT X N & P FERTILIZER AND THEIR EFFECT ON SPRING WHEAT YIELDS C.A. Campbell, W. Nicholaichuk, R.P. Zentner, G.E. Parker and J.D. Beaton Research Station, Research Branch, Agriculture Canada, Swift Current, Saskatchewan. S9H 3X2 INTRODUCTION The Canadian Wheat Board suggests that there will be a need to increase grain production by 50% between 1980-1990. At the Prairie Production Symposium held in Saskatoon on October 29-31, 1980, it was concluded that to achieve this goal farmers in the Prairie Provinces would need to do the following: · (1) Reduce fallow significantly (2) Practice better snow conservation {3) Use more fertilizer (4) Make more efficient use of fert.ilizers {5) Use more extended rotations (6) Move to more minimum tillage At Swift Current we have, for several years, been studying ways to increase the conservation of overwinter prec1p1tation. But, none of these studies involve fertilizer treatments. Similarly, we have embarked on zero till studies, but again these studies do not include fertilizer treatments. Furthermore, questions are being asked as to the e-fficacy of deep banding fertilizers and of applying fertilizer 1n the fall rather than in the spring. It was with these questions in mind that we embarked on this study with the financial assistance of the Potash and Phosphate Institute MATERIALS AND METHODS Two separate experiments, one with spring wheat and the other with winter wheat, were implemented in 1982 after establishing the stubble treatments in 1981 (Fig. 1). Only the results of the spring wheat experiment are reported here. For each crop there were 4 replicates (blocks 2.5 ha each). Each replicate consisted of a short (standard) and a tall (alternate height) stubble sub-block. Each stubble sub-block was partitioned into three year-blocks so that the experiment could be moved to previously unfertilized land each year. The Year 1 sub-blocks were 0 0 ... - 64 -divided into various fertilizer treatments to compare (a) time of application viz., fall vs spring; (b) method of N placement (broadcast vs banded); (c) rate of N; and (d) rate of P (Fig. 2). Urea was applied in case of spring wheat. In the case of Year 1 plots, P (treble super) and K (KCl) were banded at 12.5 to 15 em depth ·on a 30-cm spacing in the fall. Sulfur was broadcast in the fall. A zero-till procedure was followed. Some preliminary economic analyses were made. Yl 61 = Rep.! Y2 61 Rep.2 111 ! 1 j Short Toll -Fertilize -y 2 y I y3 y 3 y 2 yl Yl 62 • Rep.3 Y2 63 . Rep.4 Short Tall Tall Short y2 yl y3 yl y2 y3 y3 y2 yl y2 y I y3 Fig. 1. Field layout RESULTS AND DISCUSSION Growing Season Conditions The tall stubble trapped about 37 em of snow while short stubble trapped 17.5 em; however, in the spring, tall stubble only conserved about 0.9 em more soil water than did short stubble (Table 1). The 1982 growing season generally had good moisture. Precipita-tion between April and the end of August was 295 mm; the long-term average for this period is 232 mm. Rainfall distribution could have been better towards the end of the growing season. For example, rain-fall in April, May, June, July and August was 10, 82, 42, 120 and 41 mm, respectively. 22\· ..L 270' - 65 -Spring Wheat (46-0-0) ~45'--i Fall i Fall 1 Bond Brood I 1 25N r31 f-'-----)20 P20 5 1 Sprrng Spring I 2 Bond Brood I 141 I I ~lOON 151 60 P20 5 : 4 I 16 1 I I I I ~SON 11 1 120 P20 5 I 6 I raJ I I I ]__ lOON 191 120 P205 I I I 8 201 I I I .!.__100 N 211 30 P'205 I 10 [ 22 1 I I .!.L-ISQN 23 1 I 12 12~ P20 5 1 24 1 Year I (1982) Rep.l Toll N 270' I I Year 3 ( 1984) I I I I I I I I I I I I I I I I I I I I I I I I Year 2 ( 1983) I Fig. 2. Details of a Year 1 sub-block showing fertilizer treatments Grain Yields Yields as high as 3351 kg/ha (49 bu/acre) were obtained. Yields were 7% greater when fertilizer N was deep banded than when broadcast; yields were also greater when fertilizer was applied in spring compar-ed to fall (Fig. 3). Average yield for spring banded treatments was 2509 kg/ha ( 37.3 bu/ acre), for spring broadcast 2402 kg/ha ( 35. 7 bu/acre), for fall banded 2381 kg/ha (35.4 bu/acre) and for fall 0 .s::. ..... "' - 66 -broadcast 2186 kg/ha (32.5 bu/acre). The economics of these compari-sons are discussed later. Yields were increased slightly by phospho-rus (Fig. 3). But, phosphorus was more important in hastening maturity, particularly when N fertility was high (data not shown). 3000 <I' 2750 ui ,.., -i ,.., Table 1. Overwinter conservation of snow and water in tall and short stubble - 1981-82 Snow depth Water conser. in soi 1 Advantage tall over short 0 z .:- "'0 rt) .! - a. z : :! .[ 3000 2750 0 Harvest Yields Based on Avg of 2, Twa- raw Samples Per Plat Spring wheat Tall Short em 37.0 17.5 4. 7 3.8 (+ 0.9) 3000 Short 2750 • e Short ::! 2500 a. Q. : "' ~ 2500 /=;;::~·· ----~~--------6 (Avg) 4 ____ .,. • Toll 0 ...! w ;: 2250 z ~ ~ 2000 1-II) w > 1750 a:: <t :c 1500 "' ... Q d 2250 >-z ~ 2000 a:: (!) 1750 1500 /~: 2250 2000 1750 1500 25 50 100 150 N!kg/hol < 120 P2 0 5 ) T X --· I I 30 60 P2 0 5 ( kg/hal (lOON) Fig. 3. Effect of rate of N & P, method and time of N application, and height of trap strips on harvest yields. I 120 - 67 -Yields increased with N fertilizer up to 100 kg N/ha, but the 150 kg N/ha rate did not increase yield further (Fig. 3). At 50 kg N/ha or less, tall stubble treatments produced greater yields than short stubble and at rates above 50 kg N/ha the converse was true (Fig. 3). Furthermore, the average yield on year 2 and 3 "filler" plots receiving 13 kg/ha of N alone was 1418 kg/ha (21.2 bu/acre) on tall stubble and 1131 kg/ha (16.9 bu/acre) on short stubble plots. The interact ion between rate of N and stubble height on harvest yield (Fig. 3) can be explained in terms of soil water use (Fig. 4). For example, by the soft dough stage there was little available water left in the top 90 em of the soil profile at high rates of N. (The water held by this soil at wilting is 12.1 em per 90 em depth of soil). Furthermore, the moisture situation was worse in tall stubble plots than in short stubble plots, reflecting the generally greater dry matter production in tall stubble plots at each N level (Fig. 4). From August 1 to September 15 little rainfall was obtained (43 mm) to support the lush growth that had been produced at high levels of fertility. The plants grown at high N rates produced larger amounts of dry matter early in their growth thus using up available water in the profile more rapidly. Those plants grown in tall stubble grew faster due to the better initial soil water (though it was not statistically significant) and perhaps lower evapotranspiration during early growth, caused by the protection from drying winds offered by tall stubble. Furthermore, the tall stubble treatments had a greater amount of initial N03-N (data not shown). Consequently, at the 25 and 50 kg N rates soil moisture was not limiting even during the dry spell at head filling time and the advantage of tall stubble and higher N rates were apparent. However, at 100 and 150 kg N/ha rates the plants were restricted by the limited soil water that their rapid early growth had induced. Thus the extra dry matter got "trapped" in leaves and stalks instead of being translocated effectively to grain. This is evidenced in the straw/grain ratios (Fig. 5) which shows that the ratio increases with N rate and is greater for tall stubble than for short stubble, especially at the 150 kg N rate. Note also that factors that resulted in more efficient N uptake (e.g., tall stubble, banding, spring application) and which delayed maturity (data not shown) increased the straw/grain ratio. Economic Analysis The following initial economic analysis was carried out. Readers are forwarned not to overemphasize these findings since they are based on only one year's results. 13.0 12.5 ...J 0 Ill 1.1. 12.0 0 E u 011.5 (11 a.. 0 1- 11.0 z a:: LIJ !;{ 10.5 3= E u 10.0 9.5 7.5 7.0 c .:! 6.5 Cl. ..... Cl' ,_.: 6.0 3= 1-z 5.5 <( ...J a.. 5.0 T s 25 - 68 -AT SOFT DOUGH s ~ Short Stubble (S) 0 Toll Stubble ( T) s s 50 100 150 N APPLIED (kg/ ho l T S T 25 50 100 150 N APPLIED ( kg I hal Fig. 4. Effect of N fertilizer and height of trap strips on plant weight and soil water reserves at soft dough stage. (At wilting, 90 em of soil holds 12.1 em of water) 2.0 01.95 ~ Q: z 1.90 <( Q: (!) ..... 1.85 3: <( Q: 1-(f) 1.80 1.75 s - 69 -T T Br T 1. 7 o -L-L.:::....L--L--_b..~51.::-o----l-....to....-':':l o:-:o:--"----.Eo...""'7"::::--'--N APPLIED (kg/ho) FALL SPRING N FERTILIZER APPLIED Fig. 5. Effect of rate of N and P fertilizer, method and time of N application, and height of trap strips on straw/grain ratio (based on 10 plants per treatment) The assumptions and method of calculation used are outlined below: Assumptions (Base Situation) Price of wheat $184/tonne ($5/bu) Price of N fertilizer (spring and fall) $0.73/kg ($0.33/lb) Price of P205 fertilizer (spring and fall) $0.66/kg ($0.30/lb) Opportunity cost of labor (spring and fall) $12/hr Cost of broadcasting (includes complete machine rental plus all operating costs except labor) $4.32/ha ($1.75/acre) Cost of banding (includes complete machine rental plus all operating costs except labor) $14.83/ha ($6/acre) Labor requirement for broadcasting 0.124 hr/ha (0.05 hr/acre) Labor requirement for banding 0.201 hr/ha (0.08 hr/acre) - 70 -Assumptions (Seasonal Adjustment Situation) Two changes were made in our assumptions: (1) that the cost of N fertilizer would be 20% cheaper if bought in the previous fall (i.e., $0.58/kg), and (2) that the opportunity cost of labor in the fall was 50% of what it is in the spring (i.e., $6/hr). Returns above fertilizer, for each method and timing of application, was defined as: Rit =A . Yit - Ct.N- Bt.P- Li.Wt - Mi where, Rit = return above fertilizer for method i and time t ($/ha), A =price of wheat ($/kg), yit = Ct = N = Bt = p = Li = Wit = Mi = grain yield for method i and timet (kg/ha), price of nitrogen in time t ($/ha), rate of nitrogen fertilizer (kg/ha), price of phosphorus in timet ($/ha), rate of phosphorus fertilizer (kg/ha), labor requirement of method i (hr/ha), opportunity cost of labor in timet ($/hr), and cost of applying fertilizer using method i ($/ha). You will recall that when averaged over rates of fertilizer the order of yield performance was spring banded > spring broadcast = fall banded > fall broadcast. Economic analysis showed returns above fertilizer costs of > $200/ha (Fig. 6). When the base situation was used economic trends generally tracked the yield trends. Fall broad-cast N was by far the least economical, but the other treatments tended to be no different. Like yields, economic returns increased to the lOp kg N rate and then decreased at the higher N rate. When seasonal adjustments for fertilizer costs and labor were included in the analysis (Fig. 6) the fall banded N tended to out-perform the other treatments except at the 25 kg N/ha rate. Fall broadcast N was still the least economical treatment. The difference was not great for spring placement of N. CONCLUSIONS Since this study is based on only one year's data in the field we will not draw any firm cone lusions. However, there are a couple of points that should be noted: (1) trap strips may be beneficial to water use efficiency not only from a standpoint of conserving snow, but also by reducing evapotranspiration. This point requires researching; (2) trap strips may encourage lush growth in early spring and if extended periods of drought follow, plants may do less well than if they had been initially subjected to greater water stress. 28 26 - 24 ' " .<:: .;. "" 22 ~ 0 -' 20 ..... ;: IB BASE SITUATION o---o Sprin9 Broadcast N $prima Band N o-o Fall Broadcast N x-x Fall Sand N - 71 ADJUSTED SITUATION 21 26 24 22 20 IB 16·-'---.--...,.---,---r---r-----. 16~--r---r--,---r---T---~ -r;; .<:: ~ 400 0: ..... N :::i j:: 360 0: "' ... ~ 320 0 "' <l "' z 280 0: ::> .... "' 0: 240 25 50 75 100 125 150 25 400 360 320 280 240 200 -'---.---r--~--r-~--~ zoo 25 50 75 100 125 ISO 25 N FERTILIZER ( kq·ha-1) ( P205• 120 kg·ha-1) 50 75 100 125 150 50 75 100 125 150 Fig. 6. Effect of rate, method and time of application of N fertilizer on net returns (based on only one year's results) This project is Institute of Canada. ACKNOWLEDGEMENT partly funded by the Potash and Phosphate 

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Interaction of snow management × N & P fertilizer and their effect on spring wheat yields

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