To help make decisions on shifting of crop species in water management strategies, information is needed on comparative water use characteristics of the principal row crops. The objective of this study was to compare the water use characteristics of six row crops grown in a replicated and randomized field experiment. Crops were corn (Zea mays L.), grain sorghum (Sorghum bicolor (L.) Moench), pearl millet (Pennisetum americanum (L.) Leeke), pinto bean (Phaseolus vulgaris L.), soybean (Glycine max (L.) Merr.), and sunflower (Helianthus annuus L.). Crops were grown near Manhattan, KS, on Muir silt loam (Cumulic Haplustoll) in 1981 and on Eudora silt loam (JFiuventic Hapludoll) in 1982, and near Tribune, KS, on Ulysses silt loam (Aridic Haplustoll) in both 1981 and 1982.Soil water content was determined to the 3.1-m soil profile depth by the neutron attenuation method. Measured evapotranspiration (ET) was calculated as the sum of soil water depletion, rainfall, and irrigation. Reference ET was calculated by using the original Jensen-Haise equation. The maximum value of measured ET /reference ET was greater for sunflower (1.35) than for the other five crops (ranged from 1.05 to 1.15). The mean daily water use rate of sunflower (6.1 mm d-1 ) was 22% greater than the mean of the other five crops (5.0 mm d-1 ). The mean dry matter water use efficiency was 17.5 Mg ba-• m-• for the group of C 3 crops (pinto bean, soybean, and sunflower) and 33.3 Mg ba-• m-• for the group of C 4 crops (corn, grain sorghum, and pearl millet). Sunflower depleted significantly more water from deeper soil depths (0.99-1.60 m) than the other five crops at Manhattan in 1981 and 1982. Our findings consistently showed that sunflower bad a greater daily water use rate than the other five crops.

Remote sensing technology has potential for nondestructive estimation of green leaf area index (LAI). We applied the greenness transformation to ground-based reflectance data taken over seven crops (sweet and field corn, Zea mays L.; grain sorghum, Sorghum bicolor (L.) Moench; pearl millet, Pennisetum americanum (L.) Leeke; pinto bean, Phaseolus vulgaris L.; soybean, Glycine max (L.) Merr.; and sunflower, Helianthus annuus L.] grown on Eudora silt loam soil (coarse-silty, mixed, mesic Fluventic Haplodoll) to determine reflectance-LA! relationships, and to see if those relationships were crop specific or could be applied more generally to several crops. Spectral reflectance data were collected with a radiometer equipped with four wavelength bands that simulated the Landsat multispectral scanner bands. The coefficients for brightness and greenness were calculated by using reflectance data and published calculation procedures. Greenness coefficients for the reflectance data for all crops were very similar. Models were developed that related greenness (calculated by using the individual crop greenness coefficients or the coefficients developed from combined data of all crops) and field estimates of green LAI. All models were significant (PO.OS). The combined greenness coefficients were not significantly different than individual crop coefficients in relating greenness to field-estimated LAI. The crops were grouped into grass or broadleaf to determine general crop factors. It made no significant difference whether the individual crop factor or the combined crop factor (for grass, 0.197; for broadleaf, 0.117) was used in developing the greenness-estimated LAI that was related to field-estimated LAI. This study illustrated that the greenness coefficients developed for each of seven row crops were very similar and the regression coefficients from the linear relationship between LAI and reflectance greenness were very similar within the grass crops and within the broadleaf crops.

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