| In recent years, the contradiction between maize production and demand was becoming more and more prominent, the area of early season rice decreased obviously in middle and lower reaches of Yangtze River. The development of maize production is an important solution to solve the contradiction between maize production and demand in this region, so some new double cropping systems one year such as spring maize-late rice, double season maize, early rice-autumn maize emerged in this region with the rapid development of maize production in middle reaches of Yangtze River. In order to explore the extension potential of these double cropping systems in this region, four kinds of double cropping systems were used in Wuxue, Hubei province in 2013 and 2014, including spring maize-late rice(MR), double season maize(MM), early rice-autumn maize(RM) and traditional double season rice(RR). The field experiment with three replications was conducted to analyze annual yield, use efficiency of solar radiation, heat and water, and economic benefit of the four cropping systems. Meanwhile, in order to explore efficient and simplified cultivation methods of late rice of spring maize-late rice cropping system, three kinds of cultivation methods were used, including no-tillage and ordered transplanting(NOT), relay intercropping seeding(RIS) and traditional tillage and manual transplanting(TMT), to analyze the influence of the three methods on yield and economic benefit of late rice of spring maize-late rice. The main results are as follows:1. MR and MM had significant advantages in yield and photosynthetic matter production. The yield and biomass of MR and MM were significantly higher than RM and RR, MR had almost the same high yield and biomass as MM. Compared with RR, the yield and biomass of MR significantly increased by 18.3% and 18.4% separately, MM significantly increased by 13.5% and 17.1% respectively, MR and MM had significantly higher photosynthetic matter production after flowering than RR likewise. RR had nearly the same high post-anthesis photosynthetic potential as MR, significantly higher than MM and RM, but the decreasing rate of leaf area after flowering of RR was also the highest of the four cropping system.The grain yield of late rice of spring maize-late rice was significantly higher than late rice of double season rice by 6.1%, mainly due to the seed setting rate of late rice of spring maize-late rice enhanced by 7.3%. The biomass, LAI and post-anthesis photosynthetic matter production of late rice of spring maize-late were higher than late rice of double season rice, and in comparison with late rice of double season rice, late rice of spring maize-late rice had higher post-anthesis photosynthetic potential and slower decreasing rate of leaf area.The grain yield and biomass of spring maize were significantly higher than early season rice by 30.6% and 35.9%, the photosynthetic matter production after flowering of spring maize was also significantly higher than early season rice. In comparison with spring maize, early season rice had lower post-anthesis photosynthetic potential and faster decreasing rate of leaf area, but the highest LAI of early and late season rice were higher than spring and autumn maize, so in spite of post-anthesis photosynthetic source quantity of early season rice had certain superiority, but shorter duration led to faster leaf area decreasing rate. The yield of antumn maize fluctuated among different years, without regarding to autumn maize in 2014, late season rice had higher post-anthesis photosynthetic potential and faster decreasing rate of leaf area than autumn maize, autumn maize and late season rice had equivalent grain yield and biomass. So the difference in annual yield of different cropping systems was mainly due to yield difference between the first season spring maize and early season rice.2. MR and MM had significant advantages in resource use efficiency. Compared with RR, MR significantly increased solar radiation productive efficiency, solar radiation use efficiency, accumulated heat productive efficiency and water use efficiency by 14.1%, 23.4%, 16.4% and 37.2% respectively;meanwhile, MM significantly enhanced these items by 8.1%, 26.1%, 11.4%, and 88.8% respectively. The P and K use efficiency of MR and MM also had certain advantages. The accumulated heat productive efficiency and water use efficiency of spring maize were significantly higher than early season rice by 29.5% and 57.2% separately.3. MR and MM had higher and equivalent economic benefit, the economic benefit of RM and RR were lower. The economic benefit of MR and MM were higher than RR by 44.3% and 37.8%. Compared with early season rice, spring maize had higher total income, equivalent cost and higher economic benefit than early season rice by 96.1%; with higher total income and cost, late season rice had equivalent economic benefit to autumn maize.4. The grain yield of NOT and RIS were lower than TMT by 8.4% and 10.6% separately. The effective panicles of NOT and RIS were higher than TMT by 24.9% and 10.7%, but spikelets per panicle, spikelets per m2 and rate of panicle bearing of RIS were lower than TMT by 36.7%, 20.9% and 19.1% separately, spikelets per panicle and spikelets per m2 of NOT were lower than TMT by 17.8% and 9.2%. Though the biomass of NOT and RIS were lower than TMT, LAI of the three cultivation methods were equivalent. Without mechanical plowing and manual transplanting, RIS had lower cost and equivalent economic benefit to traditional TMT.Therefore, the cropping systems of MR and MM were appropriate to extend in the middle reaches of Yangtze River. As a kind of high solar efficiency C4 crop, maize replaced part of early season rice of double season rice, not only improved resource use efficiency, but also increased economic benefit and diversity of cropping system. The sowing date of autumn maize might be delayed for higher rainfall before early season rice harvesting, so there was certain risk to plant RM cropping system in middle reaches of Yangtze River. |
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