Effects of nitrogen fertilization and rice harvest height on agronomic yield indices of ratoon rice-berseem clover intercropping system

To determine the effect of nitrogen, main crop harvest height of rice and intercropping of berseem clover (Trifolium alexandrinum L.) with rice ratoon (Oryza sativa L.) on agronomic yield indices a series of field experiments were conducted at different dates in 2007-2008 and 2008-2009. The experimental design was a split-split plot with randomized complete block design with three replications. Accordingly, three levels of N (0, 35 and 70 kg ha^sup -1^) in main plots, two planting dates of berseem clover (coincident with main crop harvest and 40 days after it) in sub plots and two harvesting heights (10 and 40 cm above the soil surface) in sub-sub plots were laid out. The application of 70 kg N ha^sup -1^ and short harvest height (10 cm) yielded the highest ratoon rice grain, ratoon days to 50% heading and harvest index. The best biological yield was obtained from higher harvest height as well. Qualitative traits such as gelatinization temperature (GT) and protein content (PC) increased with large amount of N. But amylose content (AC) and gel consistency (GC) were not affected by experimental treatments. Effect of nitrogen and harvest height on fresh and dry weight of both cuts, protein content in the first cutting and total land equivalent ratio (LER) were significant at 1% level. The highest fresh and dry weight yield was obtained by application of 35 kg N ha^sup ^sup -1^^. The highest protein and total LER obtained from higher N application (70 kg N ha^sup ^sup -1^^). All studied traits had the highest value in shorter harvest height and the first planting date of berseem clover. Keywords: Nitrogen, Harvest height, Intercropping, Berseem clover, Ratoon rice. Abbreviations: GT- Gelatinization temperature; PC- Protein content; AC- Amylose content; GC- Gel consistency; LER- Land equivalent ratio; ANOVA- Analysis of variance; AAOCC- American association of cereal chemists.

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