Impacts of Basic Seedling on Yield-Scaled Greenhouse Gas Emissions from Rice Fields in China

Many researches showed a comprehensive assessment of the cropping practice effect on greenhouse gas （GHG） emissions per unit yield （yield-scaled） rather than per the land area （area-scaled）, and it was noteworthy that cropping practices decided to increase or decrease grain yield, and reduce or promote greenhouse gas emissions. In this study, a meta-analysis was conducted to quantify the effects of rice basic seedlings （BS） on the global warming potential （GWP） of GHG emissions at the yield-scale in China. The results suggested that significant difference was observed in yield-scaled GWP of BS. The lowest yield-scaled GWP occurred at 80-100 BS （415.65 kg CO2 equiv/mg）. The yield-scaled GHG emission from high to low was that of the hybrid rice varieties （1 028.86 kg CO2 equiv/mg）, the conventional rice varieties （634.15 kg CO2 equiv/mg） and the super rice varieties （576.57 kg CO2 equiv/mg）. Consequently, the model of conventional rice varieties and super rice varieties at 80-100 BS could be a scientifc method of matching inthe rice cropping system. A further assessment of rice density and variety impacts on GHG emissions at yield-scale was urgently needed to develop, so as to achieve win-win policies of rice production for higher yield with lower emissions.

Effects of Density, Fertilizer and Chemical Control on Yield of Japonica Variety 'Tongyoujing 1' and Technology Optimization

The effects of different basic seedlings, N application rates and paclobutrazol measures on the development and yield of Tongyoujing 1 population were studied through the D-saturated optimum regression design tests. The results showed thatthe effects of various factors on yield under the experimental conditions were in order of N application rate basic seedlings paclobutrazol dosage. The increases of basic seedlings and N application rate are beneficial to the increases of population quantity and tiller density, and could improve number of panicles per unit area and increase the population leaf area and accumulated amount of dry matter.However, too-high basic seedlings and N application rate would reduce reproductive tiller percentage and economic coefficient, and prolong growth duration. Proper basic seedlings could coordinate the correlation between tiller density and productive tiller percentage, ensure higher leaf area and dry matter accumulation at filling stage,and improve yield of Tongyoujing 1. According to the multivariate nonlinear regression analysis of yield with various factors, Tongyoujing 1 could reach its maximum yield potential of 12 606.0 kg/hm2 under the basic seedlings of 55.2×104/hm2, N application rate at 339.2 kg/hm2, and paclobutrazol dosage of 97.9 g/hm2. The comprehensive agricultural measures for a yield higher than 11 250 kg/hm2were： basic seedlings 52.6 ×10^4-60.1 ×10^4/hm2, N application rate 328.0-356.1 kg/hm2, and paclobutrazol dosage 87.6-104.6 g/hm2.

Density and Fertilization Optimization for Highyielding Cultivation of a Wheat Variety Heibaoshi 1

The growth period, population tiller dynamics, plant characters, paniclegrain structure, yielding ability and stress resistance of a wheat variety Heibaoshi 1 were studied using a two-factor split plot design to investigate the effects of different density and fertilizer levels on individual development and yield of Heibaoshi 1 in riparian region of Jiangsu Province. In addition, high-yielding agronomic measures were explored through multiple non-linear regression analysis. The results showed that low density was not conducive to the formation of panicles, while high density affected grain number per panicle; low fertilizer level restricted individual development, while high fertilizer level affected grain number per panicle and grain weight and was prone to leading to lodging. Reasonable combination of density and fertilizer could coordinate individual development and balance panicle, grain and weight, thus achieving a high yield. The yield potential was highest （7 384.3 kg/hm2） under density of 239.6×104 basic seedlings/hm2 and N level of 237.7 kg/hm2. When the planting density ranged from 200×104 to 270×104 basic seedlings/hm2 and the N level ranged from 220 to 260 kg/hm2 or the density basic seedling number ranged from 210×104/hm2 to 260×104/hm2 and the N level ranged from 210 to 270 kg/hm2, the yield could exceed 7 200 kg/hm2.

Analysis of Yield Components of Japonica Rice Tong Jing 981 under Different Density and Fertilization Conditions

The yield and yield components of Japonica variety Tongjing 981 under different density and fertilization levels were studied through regression and correlation and path analysis. The results showed that the number of panicles per unit area, number of filled grains per panicle and 1 000-grain weight all had very significant yield increasing effects, and the number of panicles per unit area played a leading role. However, the yield increasing effects of the number of panicles per unit area and number of filled grains per panicle are equally important when the basic seedlings are more or the N fertilizer application rate is large. In practical production, a major factor should be determined among the yield components, and rational cultivation measures should be taken accordingly, to improve yield.