The impact of source restriction on yield formation of corn (Zea mays L.) due to water deficiency

Abstract

To understand the mechanisms causing yield limitations in defoliated plants subjected to water deficiency, the experiments were laid out as a randomized complete block design with split-plot arrangement. Soil-water regimes consisted of moderate irrigation until physiological maturity (W<sub>1</sub>) or short severe water stress periods (W<sub>2</sub>) at V<sub>8</sub> stage of ontogenesis, and tasseling which allotted to the main plots. Defoliation times (V<sub>8</sub> and tasseling) and intensities (cutting of one or two thirds of leaf blade) combinations and one control level (five Source restriction treatments) were allotted to subplots. Early defoliation caused reduction in grain yield at W<sub>1</sub> and W<sub>2</sub> by 19.2 and 14.8%, respectively. On the other hand, water deficiency reduced grain per ear by 23.9% and increased individual grain weight by 37.0% (plasticity of sink capacity). These results show that under water deficiency, grain yield limitation was mostly due to a reduction in dry matter allocation to grains (sink capacity) than a result of lower dry matter production (source strength). Findings suggest that in non-irrigated corn, breeders must direct their selection program to increase grain set and decrease surplus leaves.