7The effect of reduced corn evapotranspiration (ET) during solid-set sprinkler 8 irrigation on application efficiency was analysed on two subplots. During each 9 irrigation event, one subplot was irrigated (moist treatment) while the other was not 10 (dry treatment). ET (weighing lysimeter) and transpiration (heat balance method) 11 rates were determined at each subplot before, during and after the irrigations. Zaragoza, Spain. E-mail: miriampuig81@hotmail.com 2 evaporation losses (SEL n ) were 14.4 to 17.5 % of the applied water. During night 1 time irrigations, changes in ET and transpiration were almost negligible, and SEL n 2 were slightly greater than WDEL g (9.5 % and 8.1 %, respectively, of applied water). 3 SEL n was mainly function of wind speed. Reduced ET and transpiration during 4 daytime irrigations moderately increased solid-set sprinkler application efficiency. 5

During a sprinkler irrigation event some water is lost due to wind drift and evaporation (WDEL). Aft er the irrigation event, plant-intercepted water is lost due to evaporation. Th e water lost causes microclimatic changes which could result in positive or negative plant physiological changes. We studied the microclimatic and physiological changes on two fi elds grown with maize (Zea mays L.) irrigated with a solid-set sprinkler system. Th e temperature and vapor pressure defi cit (VPD) of the air were measured at the crop canopy level and above and below the canopy. Changes in maize canopy temperature, transpiration, and leaf water potential (LWP) were determined. Sprinkler irrigation during daytime strongly modifi ed the microclimate where plants grow during the irrigation time and for a short period aft er the irrigation event fi nished. Daytime irrigation decreased air temperature by 3.3 to 4.4°C and VPD by 1.0 to 1.2 kPa at 0.5 m below the crop canopy height. Th e decrease was lower as the measurement height increased. Microclimatic changes during nighttime irrigation were minimal. Daytime irrigation reduced maize canopy temperature by 4 to 6°C and plant transpiration by 58%, and increased LWP from -1.2 and -1.4 MPa to -0.54 MPa. Transpiration reduction must be considered positive because it supposes a reduction of WDEL. Th e decrease in maize canopy temperature could be positive or negative, but the increase in LWP is a positive eff ect.

The protein nutritional value of an isolated soy protein (Supro-620) was evaluated in a series of nitrogen balance studies in healthy young male MIT students. Experiment 1 involved giving eight subjects graded intakes of the isolated soy protein while seven additional subjects received egg protein. Mean nitrogen intake required for N balance for the isolated soy protein and the egg protein were not significantly different (p greater than 0.1). In experiment 2, nine subjects received soy and the effects on N balance at various levels of L-methionine supplementation were studied. In experiment 3 eight subjects each were studied at two nitrogen intake levels of isolated soy protein/kg/day with methionine supplementation, and an unsupplemented egg protein period included. Results from experiment 2 and 3 at an 82 mg N/kg/day test level showed that N balance for 1.6% supplementation was significantly below that of unsupplemented egg while 1.1% and unsupplemented soy were indistinguishable from egg. No beneficial effects of methionine supplementation were observed when the test nitrogen intake level was 128 mg N/kg/day. These results indicate that for healthy adults, the isolated soy protein is of high nutritional quality, comparable to that of animal protein sources, and that the methionine content is not limiting for adult protein maintenance.

Nighttime sprinkler irrigation usually results in lower wind drift and evaporation losses (WDELs) and better irrigation uniformity compared with daytime irrigation. However, daytime sprinkler irrigation modifies the microclimatic conditions within the crop canopy which could result in improved crop growth. We studied the effect of daytime and nighttime irrigation on the growth and yield of maize (Zea mays L.) irrigated with a solid‐set sprinkler system. Two irrigation treatments were tested: daytime irrigation (starting at 1000 Greenwich Mean Time, GMT) and nighttime irrigation (starting at 2200 GMT). The same irrigation amount was applied in both treatments. The irrigation amount was determined as the difference between the crop evapotranspiration (ETc) and the effective precipitation. The WDELs of daytime irrigation were twice the nighttime irrigation WDELs. Daytime irrigation decreased the mean Christiansen coefficient of uniformity (CU) by 5 to 7% and the seasonal CU by 4%. Daytime irrigation caused a 10% reduction in maize grain yield, mostly due to a reduction in biomass production. The lower soil matric potential found with daytime irrigation late in the season indicated that a progressive water stress occurred that was due to less water availability and was caused by the higher WDEL for daytime irrigation. Even though positive microclimatic changes have been reported with daytime sprinkler irrigation, the results of our study indicate that they cannot compensate the negative effects caused for the crop by less water reaching the soil root zone because of increased WDEL and by poorer irrigation uniformity.

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