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The experiments were laid out to understand the mechanisms causing yield limitations imposed by post-anthesis water and nitrogen deficiencies in plants with modified source-sink ratios. two soil-water regimes were allotted to the main plots. at anthesis, three levels of n were applied: none, 25% and 50% of total the n supply. Spike-halving caused reduction in grain yield at both water regimes and all n supply levels, showing that the reduction in grain number can not be compensated by a higher individual grain weight. Sink reduction by trimming 50% of the spikelets reduced grain number per ear by 38.5% and increased individual grain weight by 12.0%, which shows the plasticity in grain weight and grain set of wheat if sufficient assimilates are available. additional nitrogen supply at anthesis had no significant effect on the total aboveground biomass, but increased grain yield through more allocation of dry matter to grains. our findings suggest that for rainfed wheat with optimum n supply and supplemental irrigation, wheat growers should choose cultivars with a high grain number per ear and manage the crop to increase grain number per unit of land (sink capacity).

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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 1 ) or short severe water stress periods (W 2 ) at V 8 stage of ontogenesis, and tasseling which allotted to the main plots. Defoliation times (V 8 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 1 and W 2 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.

This study was conducted to explore the effect of phosphate solubilizing bacteria (PSB), boron (Borax and Boric acid) and manganese (manganese chelate and manganese sulfate) based fertilizers on forage production of alfalfa. Experiment was laid in a split plot factorial in the form of randomized complete block design with phosphorus bio-fertilizer rates (0 and 100 g.ha -1 ) in main plots, while boron (0, Borax foliar application of 1.0 lit.ha -1 and Boric acid soil application 10 kg. ha -1) and manganese fertilizer (0, manganese chelate foliar application 1.0 lit.ha -1 and manganese sulfate soil application 10 kg. ha -1) were used in sub plots. The results showed that the highest dried forage yield was obtain by boron and manganese foliar application and bio-phosphorus utilization about 24.00 t/ha. Thus, triple application of PSB, Mn and B (100 g.ha -1 as soil application and 1.0 lit.ha -1 of each Mn and B solutions) could be recommended as the best treatment for improve forage yield of alfalfa (cv. Ranger) under the experiment environmental conditions.

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