Abstract
Rice–crayfish continuous production system offers high economic and ecology benefits, which developed rapidly in China. To investigate the effects of different mechanical transplanting methods and planting densities on rice yield and quality, Nanjing 2728 was used to determine rice growth performance under mechanically transplanted carpet seedling (MTCS) with equal row spacing (30 cm) at five spacings and mechanically transplanted pot seedling (MTPS) with wide and narrow rows (23 + 33 cm) at five spacings. The results showed that MTPS presented significantly higher rice yields than MTCS as more spikelets per panicle. Rice yields of both mechanical transplanting methods first increased and then reduced with decreasing planting density, and its highest value was obtained at 77.9 × 104 seedlings ha−1. Compared with MTCS at the same stage, rice tiller dynamics of MTPS first increased and then decreased. Additionally, its dry matter accumulation per stem at jointing, heading, and maturity stages, leaf area index, photosynthetic potential, crop growth rate, and net assimilation rate were all significantly higher relative to MTCS. For each mechanical transplanting method, dry matter accumulation per panicle, leaf area index, photosynthetic potential, crop growth rate, and net assimilation rate from the sowing to jointing stages declined with decreasing planting density, while dry matter accumulation per stem and net assimilation rate from the heading to maturity stages increased. Compared with MTCS, MTPS significantly improved rice milling and appearance quality, decreasing density was also beneficial to rice milling and appearance quality, while grain content of amylose and protein were not sensitive to both transplanting method and planting density. Consequently, MTPS with 13.8 cm plant spacing is a suitable mechanical transplanting method for Nanjing 2728 to obtain better yield and quality under rice–crayfish continuous production system.
Highlights
IntroductionTraditional rice cultivation could not bring high profits to farmers in China due to its general purchasing price, which negatively affected farmers’ enthusiasm for planting rice
Compared with mechanically transplanted pot seedling, mechanically transplanted carpet seedling is easier for farmers to grasp, and its investment cost is generally lower in the beginning years, and this method is widely used in traditional rice cultivation system, such as rice-wheat and rice-oilseed rape systems
Our recent practices in rice cultivation under rice-crayfish integrated farming indicated that mechanically transplanted pot seedling had an advantage than mechanically transplanted carpet seedling in adapting the special working environment, in which carpet seedling transplanted were trapped into the soil because of long-term deep water-flooding
Summary
Traditional rice cultivation could not bring high profits to farmers in China due to its general purchasing price, which negatively affected farmers’ enthusiasm for planting rice. Compared with mechanically transplanted pot seedling, mechanically transplanted carpet seedling is easier for farmers to grasp, and its investment cost is generally lower in the beginning years, and this method is widely used in traditional rice cultivation system, such as rice-wheat and rice-oilseed rape systems. It is more popular in rice-crayfish integrated farming system currently. A reasonable planting density was helpful in optimizing rice population structure, coordinate the relationship between individuals and populations, and reducing the occurrence of diseases, pests and weeds, which are important factors in obtaining high rice yield and quality [12,13]
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