秸秆还田配施不同比例化肥对晚稻产量及土壤养分的影响

在不同秸秆还田方式对早稻的效应研究确定的最佳还田方式和还田量(粉碎还田3000 kg/hm2)基础上,以单施秸秆为对照,研究了秸秆还田配施不同比例化肥对晚稻产量、干物质积累与分配及土壤养分的影响。结果表明:(1)与对照相比,秸秆3000 kg/hm2+N 150 kg/hm2+P2O575 kg/hm2+K2O 37.5 kg/hm2增产效果最为显著,在水稻的每穗粒数、千粒重、结实率、充实度和产量等方面增加幅度最大,分别为9.32%、4.28%、13.70%、2.74%和26.38%。(2)各处理的干物质茎鞘比例随着生育进程不断降低,从孕穗期的66.68%—77.00%降低至成熟期的25.97%—34.79%,除SNPK1外,叶片比例从孕穗期的23.00%—33.32%降低至成熟期的7.41%—21.03%;秸秆还田配施不同比例化肥处理的茎鞘比例在孕穗期、抽穗期和成熟期高于对照,而叶片比例与茎鞘比例呈相反趋势。(3)与对照相比,秸秆还田配施不同比例化肥处理提高了土壤pH值、有机碳、全氮、碱解氮、全磷、有效磷、全钾、速效钾,降低了土壤C/N比。研究结果说明,秸秆还田配施不同比例化肥可以提高植株干物质积累速率、群体生物量,合理改善土壤养分,保证较高的水稻增产潜力,其中秸秆3000 kg/hm2+N 150 kg/hm2+P2O575 kg/hm2+K2O 37.5 kg/hm2效果最为显著。

The effects of returning straw containing fertilizer with varying nutrient ratios on rice yield and soil fertility

Straw is rich in organic carbon, nitrogen (N), phosphorus (P), potassium (K), silicon (Si) and other nutrients that can improve physical, chemical and biological properties, increase crop yield, and lower fertilizer costs. Straw is mainly composed of cellulose, hemicellulose and lignin, and the C/N ratio is generally about 60-80; straw is therefore not easily decomposed by microorganisms in soil. Straw also needs to absorb a certain amount of N, for which it competes with crops, affecting seedling growth. Returning straw that contains a certain proportion of fertilizer N and P can mediate the soil C/N ratio, accelerate straw decomposition, and relieve the competition for inorganic nitrogen from microorganisms during the decomposition process. To explore the decomposition patterns of straw, we designed an experiment in Jiangxi to examine changes in dry matter production, soil properties, and biological processes in response to returning straw. The amount of crushed straw used (3000 kg/hm²) was determined by an examination of the effects of different amounts of returning straw on early rice. We researched the effects of returning straw containing different ratios of fertilizer on rice yield, dry matter accumulation and distribution, and soil fertility. We used a single application of straw as a control. Other treatments were SN₁ (3000 kg/hm² of crushed straw + 150 kg/hm²N), SN₂ (3000 kg/hm² of crushed straw + 225 kg/hm²N), SP₁ (3000 kg/hm² of crushed straw + 75 kg/hm²P₂O₅), SP₂ (3000 kg/hm² of crushed straw + 112.5 kg/hm² P₂O₅), SNP₁ (3000 kg/hm² of crushed straw + 150 kg/hm² N + 75 kg/hm² P₂O₅), SNP₂ (3000 kg/hm² of crushed straw + 225 kg/hm² N + 112.5 kg/hm² P₂O₅), SNPK₁ (3000 kg/hm² of crushed straw + 150 kg/hm² N + 75 kg/hm² P₂O₅ + 37.5 kg/hm² K₂O), SNPK₂ (3000 kg/hm² of crushed straw + 225 kg/hm² N + 112.5 kg/hm² P₂O₅ + 56.3 kg/hm² K₂O). The results demonstrate the following: (1) Compared with the control, the returning straw with low levels of N, P, and K significantly increase the grains per spike, 1000-grain weight, seed-setting rate, filled degree of grain and overall crop yield at rates of 9.32%, 4.28%, 13.70%, 2.74% and 26.38%, respectively. (2) The differences in dry matter accumulation between different growth periods are significant. Dry matter accumulation is greatest in the tilling to heading period and the filling to maturity period in all treatment groups.. The following proportion of total dry matter accumulation occurred in those two periods combined: 78.61%, 79.22%, 81.97%, 77.95%, 77.27%, 78.13%, 78.20%, 79.08%, and 78.47% in the control group, SN₁, SN₂, SP₁, SP₂, SNP₁, SNP₂, SNPK₁ and SNPK₂, respectively. The heading to filling period is a stage of rapid accumulation of material, but because of its short duration, dry matter accumulation and the ratio of accumulation to the total amount of dry matter was lower than in the other growth periods. With growth, the ratio of stem-sheath length to total plant length continuously decreased from a range of 66.68%-77.00% in the booting stage to a range of 25.97%-34.79% in the maturity period. In addition, in the SNPK₁ treatment, the ratio of leaf length to the total plant length reduced from a range of 23.00%-33.32% in the booting stage to a range of 7.41%-21.03% in the maturity period. The dry weight ratio of the stem-sheath to the whole plant in the booting stage, heading stage, and at maturity was significantly higher in the treatment groups than in the control group, and was highest in the SNPK₁ treatment. The dry weight ratio of the leaf to the whole plant is opposite; the ratio is highest in the control group. (3) Compared with the control group, in the treatment groups, the pH increased by 1.97%-4.33%, organic carbon content increased by 3.76%-25.05%, total nitrogen content increased by 14.75%-45.90%, alkaline hydrolysis nitrogen content increased by 3.49%-39.90%, total phosphorus content increased by 10.00%-55.00%, available phosphorus content increased by 10.45%-50.88%, total potassium content increased by 18.27%-100%, and available potassium content increased by 9.39%-79.72%; the C/N ratio decreased by 6.02%-23.59%. These results demonstrate that returning straw that contains fertilizer improves rice yield and dry matter accumulation rates; this translates to a higher potential yield of rice crops, and an increase in the level of soil nutrients. The combined effect of returning rice straw to fields with low levels of N, P, and K is significant. This study will provide a theoretical basis for the use of straw to increase soil fertility in southern regions of China, where rice farming is abundant.