A drought experiment using mobile shelters: the effect of drought on barley yield, water use and nutrient uptake

Abstract

Automatic mobile shelters were used to keep rain off a barley crop in a drought experiment. The treatments ranged from no water during the growing season to regular weekly irrigation. This paper reports the effect of drought on the harvest yield and its components, on water use and nutrient uptake.Drought caused large decreases in yield, and affected each component of the grain yield. The magnitude of each component varied by up to 25 % between treatments, and much of the variation could be accounted for by linear regression against the mean soil water deficit in one of three periods. For the number of grains per ear, the relevant period included tillering and ear formation; for the number of ears per unit ground area, the period included stem extension and tiller death; for grain mass, the period included grain filling.The harvest yields were linearly related to water use, with no indication of a critical period of drought sensitivity. The relation of grain yield to the maximum potential soil water deficit did show that a prolonged early drought had an exceptionally large effect on both yield and water use.Two unsheltered irrigation experiments, also on barley, were made in the same year on a nearby site. The effects of drought on yield in these experiments were in good agreement with the effects observed on the mobile shelter site.When fully irrigated, the small plots under the mobile shelters used water 11 % faster than larger areas of crop, because of advection. The maximum depth from which water was extracted "was unaffected toy the drought treatment. When 50 % of the available soil water had been used the uptake rate decreased, but the maximum depth of uptake continued to increase.Measurements of crop nutrients at harvest showed that nitrogen uptake was large, because of site history, and that phosphate uptake was decreased by drought to such an extent that phosphate shortage may have limited yield.

Suitability Assessment of Satellite-Derived Drought Indices for Mongolian Grassland

“…Drought had a substantial influence on maximum measured aboveground biomass production [34,35]. However, biomass data reflect vegetation conditions in different areas at different times, and are limited in terms of spatial and temporal comparability with drought indices.…”

“…Drought had a substantial influence on maximum measured aboveground biomass production [34,35]. Since absolute biomass data had shortcomings of spatial and temporal comparability, we developed a normalized biomass (NorBio) for the assessment of grassland drought along similar lines to the development of the VCI equation as a normalized calculation using long-term data.…”

“…However, for the drought indices, obtaining real drought values in a field campaign is difficult; thus, we assessed drought using other reference data. Normally, soil moisture was correlated with agricultural or vegetation drought [34]. Soil moisture in the field can reflect crop or vegetation drought, which also represent an effective method of evaluating grassland drought.…”

Estimating crop coefficients for corn during an evapotranspiration experiment on an oxisol in Brazil

“…Many authors have presented methods to estimate and separate these two variables. The field capacity method, which held that downward flow or drainage virtually ceased after two or three days, has been succesfully used by DAY et al, (1978) and FRANCIS & PIDGEON (1982a). Nevertheless, the downward flow out of the root zone (drainage) is not always negligible and often constitutes 20% or more of the field water balance even under a normal water regime (REICHARDT et al, 1974).…”

Optimum irrigation period for grain production in spring wheat

“…This situation does not allow for precise field investigations, especially in attempts to determine whether there are critical stages in crop development, at which even a small amount of irrigation water exerts a significant effect on the yield. Many researchers, therefore, have attempted to prevent field experiments from being affected by rain by using shelters to determine the optimum irrigation time or growth stage (Spratt and Gasser 1970;Wells and Dubetz 1970;Day et al 1978), though the crop micro-climate may be influenced by prolonged covering .…”