Assessment Of Ryegrass-rice Cropping Systems And Simulation For Management

Ryegrass-rice cropping system is rapidly developed in middle-and-lower reaches of Yangtze River in recent years. Field experiments were carried out to discuss the productivity of ryegrass under different rates of nitrogen fertilizer, the effects to after-crop rice of planting ryegrass and the synthesis benefits of ryegrass-rice cropping system. The simulation models for ryegrass-rice were developed. The main results are showed as follows:The nitrogen contents of ryegrass's leaves were higher than that of wheat's at the same stage, ryegrass's dry matter accumulation and LAI were lower than wheat's in early stage, but tend to higher in later stage under no-cutting condition. Compared to no-cutting ryegrass, cutting ryegrass's total amount of N uptake increased rapidly in later growing period. No matter cutting or no-cutting conditions, ryegrass's dry matter accumulation, LAI, leaf nitrogen contents and total amount of N uptake were increased as nitrogen rates increased.At different nitrogen rates, the full grain percentage and thousand-grain weight were both higher under wheat stubble than under ryegrass stubble, but the numbers of spikelets per panicle were opposite. The yields of rice cultivars Wuyujing-3 and Huajing-3 were higher under ryegrass stubble than under wheat stubble, cultivars 9522 and Xiangjing-49 were reversed. At maturing stage, rice cultivars Wuyujing-3 and Huajing-3's total amounts of N uptake and dry matter were higher under ryegrass stubble than under wheat stubble; cultivars 9522 and Xiangjing-49 were reversed. At the same N level, the leaf nitrogen contents of four rice cultivars were lower under ryegrass stubble than under wheat stubble at early stage, but opposite at late stage.Ryegrass- rice cropping system can enhanced organic matter, total nitrogen and alkali-hydrolyzable nitrogen, but decreased rapidly available P and rapidly available K than wheat-rice cropping system. On direct sowing condition, at N1, N2, N3, N4 level,the mounts of ryegrass's digestible energy were increased by 15.38%, 31.25%, 47.37% and 66.67% respectively, compared with that of wheat grain. At Nl and N2 levels, ryegrass's benefits were lower than wheat's, but higher at N3 and N4 levels. At N4 level, the benefits of under-crop sowing ryegrass was higher 28.17% than that of direct sowing ryegrass.The simulation models of ryegrass were established about phenology, photo-synthetic production, dry matters accumulation and nitrogen uptake. The management countermeasures were put forward for ryegrass- rice cropping system.