Objective:                   

To evaluate water use response of spring wheat varieties on yield and quality

Methods:                    

Eight spring wheat cultivars were grown under six irrigation levels as a split plot, randomized complete block design with four replications, where irrigation levels represent the whole plot and the eight spring wheat varieties were the sub plot factor.  The irrigation levels were full irrigation (100ET, FullIrr), deficit irrigation (66ET, 2/3FullIrr), various levels of early irrigation termination events (FullIrr-1, FullIrr-2 FullIrr-3) and a rainfed check. The daily potential evapotranspiration was monitored (Creston Weather Station) and daily crop water use was determined using a crop coefficient approach. To trigger irrigation, daily soil water balance was calculated and plant water availability was maintained above 50% in treatment 100ET and irrigated 1.25 inches each irrigation event. The deficit irrigation followed the same schedule with 100ET, except 0.85 inch was applied for each irrigation event. The FullIrr-3, FullIrr-2, and FullIrr-1 were terminated on June 23, July 6, and July 13, respectively. Details of agronomic management is shown in Table 1. The cumulative amount of water in the dryland and irrigated treatments is shown in Figure 1.

 

Table 1: Material and Methods   

Seeding Date: 4/22/2015 Herbicide:  5/20/2015
Julian Date: 112 13.7 fl oz/A Huskie complete + 0.5 lb/A AMS
Seeding Rate: 20 plnts/sqft Pesticide:    6/19/2015
Previous Crop: Canola 12 fl oz/A Quadris + 1.92 fl oz/A Warrior II  
Tillage: Conventional
Irrigation: Yes
Soil Type: Fine sandy loam Harvest Date: 8/13/2015
Soil Test: 19-6-111 Julian Date:  225 
Fertilizer: 281-48-115

 

 

Line graph showing the cumulative rain and irrigation treatments relative to crop water use

Figure 1. Cumulative rain and irrigation treatments relative to crop water use (Crop ET)

Summary:

            The irrigation main effect was significant among all agronomic traits except protein, still the expected relationship between yield and protein was observed. Volt had the highest yield response while Brennan yielded the least consistently across all water regimes (Figure 2). The maximum yield response was when total plant available water was at 11 inches (Figure 3).

Among varieties, Volt had the highest yield but with the lowest protein due to dilution effect of these two factors. Test weight increased with irrigation, but late season irrigation events that occurred during milk and early dough (FullIrr-1 and FullIrr, respectively) on average decreased test weights, Expresso was the exception.

  Heights ranged from 19.8 inches for Cabernet under dryland treatment to 29.4 inches for McNeal under FullIrrig-2 treatment. An interaction between irrigation and varieties was observed for falling number. All varieties had falling number greater than 250 seconds. McNeal had highest falling number for all treatments. Late season rainfall that would have triggered preharvest sprout was lacking. No visible plant lodging was observed.

            A significant interaction between irrigation and variety for protein was observed. Late season irrigation appears to increase protein selectively with varieties.  An expected relationship between seed size and yield was observed (compare TKW or SS with yield in Table 2). As yield increased with irrigation, seed size decreased due to increased number of seeds per unit area, whereas seed size increased when number of seeds per unit area decreased for low yield.

 

Table 2. Spring wheat water use effects on agronomic performance         

  HT PM* SS MC YLD PRO TWT TKW FN
Cultivar in days seeds/lb % bu/A % lb/bu g sec
Full Irrigation (Fullirrig)
Brennan 21.3 84 12517 11.1 58.5 15.8 62.5 36.3 411
Buck Pronto 26.2 84 11295 10.6 68.5 14.4 62.0 40.8 366
Cabernet 20.7 84 12446 11.4 64.6 13.8 62.7 36.6 311
Expresso 26.5 86 11354 11.1 85.0 14.9 62.8 40.0 305
McNeal 28.2 87 11003 11.3 81.4 14.3 61.7 41.6 470
Solano 22.1 86 10975 11.9 77.2 14.3 62.4 41.4 334
Volt 26.8 86 12503 13.0 87.8 13.5 62.4 36.3 349
WB Rockland 23.1 88 10735 13.6 71.5 15.7 60.3 42.3 300
Deficit Irrigation (2/3 Fullirrig)
Brennan 21.2 83 12755 10.6 52.4 16.1 62.7 35.6 402
Buck Pronto 25.8 83 10778 10.5 73.4 14.8 61.8 42.1 382
Cabernet 20.2 82 12951 10.4 61.0 13.6 63.0 35.1 316
Expresso 24.7 83 12027 11.2 78.1 14.2 62.6 37.8 301
McNeal 28.4 85 11286 10.6 79.1 14.1 61.9 40.4 504
Solano 22.8 85 11316 10.6 77.3 14.2 62.8 40.2 356
Volt 25.9 85 12622 11.4 80.7 13.0 63.5 36.0 385
WB Rockland 23.0 85 10882 12.4 66.5 15.8 60.9 41.8 292
One Irrigation Event Terminated Early (Fullirrig-1)
Brennan 21.3 84 12322 10.6 58.8 15.9 62.9 36.9 421
Buck Pronto 25.6 84 10959 10.6 70.5 14.6 62.1 41.5 367
Cabernet 21.3 83 12539 10.6 70.2 13.7 63.3 36.4 320
Expresso 25.0 85 11854 11.5 78.6 14.6 62.3 38.4 277
McNeal 28.4 87 11390 11.2 84.0 13.9 61.7 40.1 517
Solano 23.0 85 11356 12.7 76.1 14.6 61.3 40.1 323
Volt 27.2 86 12550 12.2 90.4 13.4 62.9 36.2 371
WB Rockland 22.8 87 10977 11.0 67.9 15.2 61.5 41.4 290
Two Irrigation Events Terminated Early (Fullirrig-2)
Brennan 21.1 83 12553 10.5 57.4 15.7 62.7 36.2 425
Buck Pronto 25.6 83 11519 10.3 68.4 14.0 62.1 39.6 376
Cabernet 21.3 82 12337 10.5 70.5 13.7 62.8 36.9 321
Expresso 25.4 86 12049 11.5 76.5 14.6 61.9 37.7 349
McNeal 29.4 87 11271 11.0 86.7 13.7 61.8 40.3 521
Solano 23.3 86 11556 10.6 79.8 14.2 62.9 39.3 355
Volt 26.9 87 13754 11.2 80.9 13.0 63.5 33.1 393
WB Rockland 22.9 87 11966 12.3 70.8 16.0 61.0 38.2 313
Three Irrigation Events Terminated Early (Fullirrig-3)
Brennan 21.2 79 12597 10.7 49.7 15.3 62.6 36.2 413
Buck Pronto 25.3 81 11510 10.3 63.4 14.9 61.3 39.5 384
Cabernet 20.6 81 12609 10.6 63.4 13.5 62.6 36.1 359
Expresso 23.8 83 12428 10.7 69.6 14.6 62.0 36.7 310
McNeal 26.2 81 12270 11.5 70.0 13.9 60.7 37.4 471
Solano 23.3 83 12419 10.7 68.3 14.2 62.3 36.7 354
Volt 25.2 82 13204 10.8 78.8 13.1 63.4 34.6 400
WB Rockland 21.1 83 11556 11.7 65.7 15.3 61.4 39.4 324
Dryland
Brennan 20.5 76 14993 10.3 25.5 15.4 61.8 30.3 449
Buck Pronto 22.7 78 12645 10.0 36.2 14.8 61.2 36.0 399
Cabernet 16.7 76 14765 10.3 25.6 14.3 61.2 30.7 361
Expresso 20.8 79 12451 10.1 33.0 15.5 61.3 36.6 298
McNeal 25.1 80 13343 10.2 34.4 14.5 60.7 34.2 535
Solano 20.1 77 12455 10.0 34.6 15.4 61.6 36.5 381
Volt 22.0 79 14479 10.1 40.7 13.3 63.1 31.4 416
WB Rockland 19.8 79 11860 9.8 29.2 16.1 61.3 38.3 323
CV 13.4 4.3 10.0 11.1 28.3 6.7 1.8 9.7 18.9
LSD 1.4 2.8 715.8 0.8 6.3 ns 0.6 2.4 27.0
Pr>F(0.05)-Irr <.0001 <.0001 <.0001 0.0002 <.0001 0.3347 0.0056 <.0001 0.0026
Pr>F(0.05)-Var <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001
Pr>F(0.05)-IrrxVar 0.8163 0.7680 0.0115 0.2475 0.3060 0.0035 0.2655 0.0972 0.6269
HT; height, PM: physiological maturity *(duration from emergence), SS: seed size, MC: moisture content, YLD: yield, PRO: protein, TWT: test weight, TKW: thousand kernal weight, FN: falling number, ns: nonsignificant         

 

Bar graph showing the yield response to water use efficiency of spring wheat on fine sandy loam soil

Figure 2. Yield response to water use efficiency of spring wheat on fine sandy loam soil

 

Graph showing the yield response of spring wheat to water regimes on fine sandy loam soil

Figure 3. Yield response of spring wheat to water regimes on fine sandy loam soil