Effects Of Straw Mulch And Water-nitrogen Fertilizer Management On Yield Of Rice, Grain Quality And The Properties Of Soil

The effect of straw mulch and water, nitrogen management on hybrid rice (F you 498) nitrogen (N) uptake and utilization and grain yield and quality and the physicochemical and properties of soil were evaluated. Three experiments were conducted in paddy field of the Rice Research Institute of Sichuan Agricultural University in 2013-2014 as below.:(1) The effect of straw mulch and N-management on grain yield and quality and soil physicochemical and properties; a split-plot design with three replication was used in this study in 2013, the main plots under wheat straw mulch (S1), rape straw mulch (S2) and no straw mulch (So), N management as sub-plots combined with three N management practice under 135 kg/ha N rate in this study. The three N application ratios was applied on different splits:(a) 3 splits:50% basal,30% 7 d after transplanting (7 DAT), and 20% panicle N-fertilizer according to different leaf age at 4th leaves emerged from the top (N1), (b) 3 splits:30% basal,30% 7 DAT,40% panicle N-fertilizer at 4th leaves emerged from the top (N2), (c) 4 splits:30% basal,10% 7 DAT,60% panicle N-fertilizer equally at 4th and 2nd leaves emerged from the top (N3), in addition, no N application (No) was set as control. (2) Effects of wheat straw mulch and N-management on grain yield and quality and soil physicochemical under different soil fertility conditions (2013). A split-plot design was used at each fertility level, with wheat straw mulching as the main plot and no wheat straw mulching as control, and N-fertilizer management (the same as the first experiment) as sub-plots. (3) The effect of irrigation methods and nitrogen-straw mulch management patterns on grain yield and quality and soil physicochemical and property. A split-plot design was used in the study in 2014.the main plots under flood irrigation (W1), alternate wetting and drying irrigation (W2), drought irrigation (W3), nitrogen-straw mulch management pattern as sub-plots combined with wheat straw mulch, rape straw mulch, and no straw mulch with N2 nitrogen management under 135 kg/ha N rate in this study, and with No as control. The relationship between N translocation rate and root growth in different periods; and the relationship between grain quality and leaf SPAD values at grain filling stage were also investigated in this paper. The main research results are as follows:1 Effects of straw mulch and water-nitrogen management pattern on grain yield and yield componentsWheat straw mulch generally improves the effective panicle number and spikelet, and increases grain yield significantly, but which under high fertility condition get more remarkable influential, the rape straw mulch also increases grain yield significantly, but not as much as wheat straw much. And both straw mulch practice combine with N2 management were highly increase the grain yield and improve the water use-efficiency. As for the irrigation practice, alternate wetting and drying irrigation method increases the effective panicle and spikelet and grain yield, and improves the water use-efficiency efficiently. And under flooding irrigation and alternate wetting and drying irrigation methods with wheat straw mulch and N2 management pattern were get more remarkable yield-increasing effect than other nitrogen-straw mulch pattern, especially under alternate wetting and drying irrigation method. But under drought irrigation method, rape straw mulch and N1 management pattern is the optimal nitrogen-straw mulch pattern.2 Effects of straw mulch and water-nitrogen management pattern on rice growthWheat straw mulch and rape straw mulch significantly improves dry matter transportation in stem and sheath and nitrogen use-efficiency, increases total dry matter accumulation and nitrogen uptake, regulates and delays the senescence of root, and coordinates the SPAD value of flag leaf in filling stage. But In the former rice growth stage, straw mulch inhibits the rice root growth and morphology construction, decreases dry matter accumulation and nitrogen uptake, and the lower soil fertility get higher inhibition. As for N management practice, N 30%basal,30% 7DAT,40% panicle N management practice (N2) was the optimal N-fertilizer management practice in all straw mulch treatments. It regulated the root growth on main growth stage efficiently, improved dry matter transportation in stem and sheath, and promoted N-utilization efficiency. When panicle N-fertilizer ratio increased to 60%, root growth was poor, especially on heading stage, it decreased grain yield and N-utilization. Under different irrigation methods and nitrogen-straw mulch patterns, alternate wetting and drying irrigation method association with N2 management significantly increases dry matter accumulation and nitrogen uptake, regulation the up and under-ground biomass growth, and the flood irrigation method follows. The correlation coefficients among root growth, N-uptake and utilization and grain yield were as follows; under straw mulch and N-fertilizer management, the root dry weight and total root volume and total root length generally have significant or extremely significant positive correlation with grain yield and N-uptake and utilization on main growing stage of rice(r=0.38*～0.78**).3 Effects of straw mulch water-nitrogen management pattern on rice qualityWheat straw mulch and rap straw mulch generally improves the rice quality, Especially in high soil fertilizer condition, it more highly increased the rice N uptake and grain yield, and more heavily decreased the grain percentage of chalky kernel and chalkiness degree. To the N management aspect, wheat straw mulch with N2 management all increased grain yield and the rice flag leaf SPAD on grain filling stage, promotion N-uptakes and utilization efficiency and the grain quality generally. Furthermore, in low soil fertilizer condition, wheat straw mulch with N1 also get higher inspect on decrease the grain Percentage of chalky kernel and chalkiness degree. Under different irrigation methods, alternate wetting and drying irrigation method and drought irrigation methods significantly improve the rice quality, but alternate wetting and drying irrigation method much better than drought irrigation method, and for nitrogen-straw mulch pattern, N2 associates with wheat and rape straw mulch generally improves the grain quality, but N2 with wheat straw mulch is much better than rape straw mulch, especially under alternate wetting and drying irrigation method and drought irrigation method. The correlation coefficients between grain quality and SPAD of flag leaf on filling stage shows, on the filling stage, the rice flag leaf SPAD generally have significant or extremely significant positive correlation with the percentage of brown rice and head rice, and have some negative correlation with the grain Percentage of chalky kernel and chalkiness degree, but generally not significant, and the most correlation between flag leaf SPAD and grain quality under different soil fertilizer condition all appeared in the middle of the filling stage.4 Effects of straw mulch and water-nitrogen management pattern on straw decomposition and nitrogen releaseThe decomposition and nitrogen release of wheat straw mulch and rape straw mulch both shows:in the former stage straw decompose and N-release very fast, but along the rice growth, the both speed were slow down, and the wheat straw decomposition and N-release accumulation and speeding under high soil fertility were generally higher than under low soil fertility condition. Compare with rape straw, wheat straw get lower decomposition accumulation and decomposition speed in the former stage, yet in the following stage was get much better, and both straw mulch associate with N2 significantly balance the straw decomposition and nitrogen release rate and speed. Under different irrigation methods, in previous growth stage, flooding irrigation method and alternate wetting and drying irrigation method generally get much higher decomposition and nitrogen release rate and speeding. But in the later time, straw under drought irrigation method get much better on decomposition and nitrogen release rate and speed. As for the nitrogen-straw mulch pattern, straw mulch associate with N2 significantly balance the straw decomposition and nitrogen release rate.5 Effects of straw mulch and water-nitrogen management on soil physiochemical propertyBoth wheat straw mulch and rape straw mulch generally decreases soil pH, and it also decrease the variation range of soil pH in low soil fertility and high soil fertility, especially in wheat straw mulch. While in the soil total nitrogen content aspect, nitrogen release of straw can improve the 0-10cm soil nitrogen content, and also can obviously promote the downward movement of soil nitrogen, improve soil total nitrogen content of 10-20cm. As for the nitrogen-management, N2 can balance the rice nitrogen uptake and soil nitrogen content. And under different irrigation methods, the total soil nitrogen content increased both under flooding irrigation method and drought irrigation method, but flooding irrigation method much better than drought irrigation, and wheat straw mulch and rap straw mulch both association with N2 can balance the rice nitrogen uptake and soil nitrogen content in all the soil layer under different irrigation methods.