Effect of sowing date and density on matter accumulation and translocation and on yield of chickpeas

This study explores the effect of sowing date and density on matter accumulation and translocation and the yield formation of chickpeas. Determining the optimum sowing date and density for chickpeas planted in Northeast China will lay a foundation for promoting the cultivation of chickpeas and the development of the chickpea industry. Four sowing dates (March 29th, April 7th, April 16th and April 25th) and four sowing densities (16.7×10⁴ plants·hm^-2, 11.1×10⁴ plants·hm^-2, 8.3×10⁴ plants·hm^-2 and 6.7×10⁴ plants·hm^-2) were set during 2018 and 2019. 'Baiying 1' chickpea was as material, and the growth process, photosynthetic characteristics, population quality, carbon and nitrogen translocation, and yield formation of 'Baiying 1' chickpeas during different growth periods were determined through by measuring dry matter content, leaf area index, yield components, and the content of chlorophyll, soluble sugar, starch, and total nitrogen. The date of seedling, flowering, and maturity were delayed as the sowing date was delayed, the growth period was shortened, and pods per plant initially increased, and then decreased. With the growth of chickpeas, the chlorophyll content and leaf area index of different treatments first increased and then decreased. The dry matter accumulation in the vegetative organs of chickpeas planted early was lower than in those planted late. Therefore, later sowing increased the contribution of nitrogen amount accumulated post-anthesis to the grain nitrogen. Further, the dry matter accumulation of chickpeas planted with high density was lower than those planted with low density. Decreased density promoted increased translocation, rate of pre-anthesis assimilation, and nitrogen accumulated post-anthesis. The regression equation of sowing date (X₁), density (X₂), and yield (Y) was Y=-150.288 9+47.169 3X₁+ 464.092 5X₂-1.499 9X₁²-11.376 4X₂²+ 1.292 2X₁X₂. In summary, the dry matter accumulation of chickpeas planted with intermediate and late sowing dates was higher than those with intermediate and early sowing dates. With delayed sowing date, the soluble sugar accumulation and starch content in seeds decreased, and the redistribution amount and efficiency of nitrogen accumulated pre-anthesis stored in stems and leaves first increased and then decreased; however, the contribution of nitrogen accumulated post-anthesis to the grain nitrogent of chickpea increased. The effect of translocation on the yield of pre-anthesis of chickpeas planted with medium and low density was large, and the amount of nitrogen accumulated post-anthesis was high. Moreover, the effect of post-anthesis assimilate accumulation of chickpeas planted with medium and high density on yield was significant. The contribution of redistribution of nitrogen accumulated pre-anthesis to grain nitrogen of chickpeas planted with intermediate and early sowing dates with medium density or intermediate and late sowing dates with high density increased. Under the conditions of this experiment, the optimal cultivation of 'Baiying 1' occurred when sown on April 23th, with a density of 7.64×10⁴ plants·hm^-2. However, this could vary with differing local geographical, climatic, and other environmental factors.