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One of the challenges to improve sweet corn [Zea mays var. Saccharata (Sturtev.) L. H. Bailey] production is finding a way to increase crop establishment and decrease weed infestation. Crop establishment and weed control are of prime importance in sweet corn production. Three methods of seedbed preparation including pre-planting irrigation before ridge-furrow preparation, pre-planting irrigation after ridge-furrow preparation and irrigation after planting, and four wheat (Triticum aestivum L.) residue rates (0, 250, 500 and 750 g/m2) were arranged in a split plot based on a randomized complete blocks design. Higher seedling emergence and weed control were significantly obtained in pre-planting irrigation than irrigation after planting treatments. Wheat residue mulching reduced soil moisture depletion, proline and soluble carbohydrates contents with decreasing weed biomass. The efficiency of weed management was found to be ensured using pre-planting irrigation coupled with wheat residues application. The grain yield was the highest (1433 g/m2) using pre-planting irrigation and wheat residue mulching (750 g/m2). Weed biomass decreased by 58% in pre-planting irrigation after ridge-furrow preparation and wheat residue mulching (750 g/m2) compared to irrigation after planting and no-mulching treatment. Therefore, pre-planting irrigation after ridge-furrow preparation and wheat residues application (500–750 g/m2) were optimal management practices for crop establishment and weed control to improve yields and water productivity of sweet corn in the region.

Introduction: Sweet corn (Zea mays var. saccharata) is a corn variety that is distinguished from other varieties due to the presence of genes that affect starch production in the endosperm. Given that the most of plants including sweet corn face with problems such as non-uniform germination and poor seed emergence in the early stages of germination. Thus, the use of organic stimulants is one of the ways to reduce the harmful effects of non-biological stresses, increase seed germination, uniform appearance and increase their yield and quality. The present study was carried out to investigate the effect of different concentrations of chitosan on seed germination and some biochemical traits of sweet corn under osmotic potential conditions. Materials and Methods: To investigate the effect of chitosan and osmotic stress on germination and biochemical parameters of sweet corn, a factorial experiment was conducted in a completely randomized design with four replications at the Seed Technology Laboratory, Faculty of Agriculture, Yasouj University in 2017. The first factor was osmotic stress at 0,-3,-6, and-9 bar osmotic potentials and the second factor was pre-treatment at five levels of chitosan zero, 0.25%, 0.5%, 0.75% and 1% and one level of distilled water. The seeds were immersed in the desired solutions of chitosan for 3 hours at 25 °C and under dark conditions, and then the pre-treated seeds were germinated under standard germination condition. In each petri dish, 25 seeds were placed on a filter paper and osmotic potential was applied using polyethylene glycol 6000. Seed germination was carried out in the germinator at 25 ± 1 ° C for 7 days under dark conditions. The germination traits and biochemical traits were measured according to standard methods. Results: Osmotic stress reduced germination percentage and germination rate, seedling vigour length index, germination uniformity coefficient, allometric coefficient, and soluble protein content and also increased the mean germination time, proline, soluble sugar content and hydrogen peroxide. Pre-treatment of seeds with a concentration of 0.5% chitosan increased protein, proline, and soluble sugars content at all osmotic stress levels. At the osmotic stress levels, the highest and lowest levels of hydrogen peroxide respectively were observed in 0.5% chitosan treatment and distilled water treatment. The results showed that pre-treatment with 0.5% chitosan increased germination percentage and rate and seedling vigour length index, and also reduced the mean germination time and malondialdehyde. Pre-treatment of seed with zero and 1% chitosan led to reduction in some of the germination and biochemical traits in comparison with 0.25, 0.5, and 0.75% chitosan. Conclusions: The results showed that seed treatment with 0.5% chitosan could reduce the harmful effects of osmotic potential on some germination and biochemical traits in sweet corn seedlings and improve seedling growth.

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In order to investigate the effect of planting date and sowing method on ear yield, water use efficiency and some physiological characteristics of sweet corn, an experiment was carried out as a split plot based on a randomized complete block design with three replications in Yasouj, southwest of Iran. Planting date consisted of five levels (4 May, 19 May, 4 June, 19 June, 5 July) and considered as the main plots and three levels of planting methods (seed cultivation, transplanting cultivation [15-days after planting (3-leaf stage)] and [20-days after planting (4-leaf stage)] were assigned to the sub-plots. Planting date and sowing method interaction effects were significant on ear yield and water use efficiency. Transplanting at 3-leaf stage on the 4th of May had the maximum ear yield (16000 kg ha-1) and at 4-leaf stage on the 5th of July had the minimum ear yield (8000 kg ha-1). The highest water use efficiency (2.93 kg m-3) was obtained by transplanting on the 4 th of May and 3-leaf stage, which was 66% higher than the water use efficiency of those transplanted on the 5th of July and at 4-leaf stage. The effects of planting date and sowing method were significant on grain protein content. With a delayed planting, the grain protein content was increased so that the maximum of grain protein content (8.7%) was obtained in the 5 th of July and the lowest (8%) in the 4th of May transplanting. The grain protein concentration of the transplanting treatments was less than the grain protein of the seed cultivation treatment. The high temperature stress experienced by sowing at the 19 th of May until the 19 th of June decreased the grain sugar content. Transplanting cultivation led to increase in the amount of total sugar compared to seed cultivation. The best treatment in this study was found to be transplanting at 3-leaf stage on the 4 th of May.