View Full Table | Close Full ViewTable 1.

Hypothetical grain yield, evapotranspiration (ET), transpiration/evapotranspiration ratio (T/ET), transpiration efficiency, and harvest index (HI) values for grain sorghum and corn grown in U.S. southern Great Plains.

 
Crop and location Grain yield† ET T/ET TR HI
kg ha–1 dry wt. mm ha–1 kg H2O kg biomass–1 kg grain kg biomass–1
Grain sorghum
 Bushland, TX 1,680 250 0.55 258 0.35
3,010 350 0.57 239 0.40
4,350 450 0.59 248 0.45
5,680 550 0.60 251 0.48
 Tribune, KS 1,650 250 0.54 281 0.38
  (Conventional 2,750 350 0.56 274 0.42
 Tillage) 3,860 450 0.58 274 0.45
4,970 550 0.62 296 0.48
 Tribune, KS 1,480 250 0.50 290 0.38
 (No-Till) 3,060 350 0.63 275 0.42
4,640 450 0.69 271 0.45
6,230 550 0.72 275 0.48
Corn 380 300 0.55 273 0.07
 Bushland, TX
2,460 400 0.59 256 0.30
4,540 500 0.62 242 0.40
6,620 600 0.64 232 0.45
8,710 700 0.66 235 0.50
10,790 800 0.67 234 0.53
12,020 900 0.68 230 0.55
 Nebraska 3,170 300 0.60 225 0.44
4,730 400 0.62 208 0.46
6,290 500 0.64 220 0.48
7,840 600 0.66 228 0.50
9,400 700 0.67 234 0.52
10,960 800 0.69 245 0.54
12,520 900 0.70 249 0.55
Grain yield (GY) and ET amounts were calculated from relationships based on field studies for grain sorghum grown at Bushland, TX (Stewart and Steiner, 1990), and Tribune, KS (Stone and Schlegel, 2006); and corn at Bushland, TX (Howell and Tolk, 1998), and various locations in Nebraska (Grassini et al., 2011); HI values T/ET ratios estimated based on review of literature, and transpiration ratio (TR) values were calculated as an unknown using GY = ET × T/ET × 1/transpiration ratio (TR) × HI.



View Full Table | Close Full ViewTable 2.

Hypothetical values of components in equation GY = ET × T/ET × 1/TR × HI for corn production in areas of increasing annual precipitation.†

 
Components Precipitation, mm
500 600 700 800 900 1,000
ET, mm 320 375 435 500 570 650
T/ET 0.55 0.58 0.61 0.64 0.67 0.70
TR, kg water/kg biomass 270 258 246 234 222 210
HI 0.44 0.46 0.48 0.5 0.53 0.55
GY, kg ha–1 dry wt. 2,860 3,860 5,160 6,820 9,090 10,580
GY = grain yield; ET = evapotranspiration; T = transpiration; TR = transpiration ratio; HI = harvest index.