平衡施肥对缺磷红壤性水稻土的生态效应

为了研究平衡施肥对缺磷水稻土的生态效应，对长期缺施磷肥水稻土进行了3.5年平衡施肥试验。试验采取盆栽水稻的方式，在长期缺施磷肥的红壤性水稻土上比较不施磷肥（NK）、平衡施用氮磷钾无机肥（NPK）、无机氮磷钾肥配施硅肥（NPKSi）、无机氮磷钾肥配施有机肥（无机肥占3/5）、NPK基础上增施磷肥（NKhP）、NPKM基础上增施磷肥（NKhPM）处理的土壤肥力、土壤微生物特性、土壤磷的渗漏量以及地上部水稻产量、养分利用率、磷肥利用率的变化。试验表明，平衡施肥处理NPK、NPKSi、NPKM、NKhPM显著提高水稻产量，比不施磷肥（NK）平均增产147%，其中NPKM提高152%；能提高土壤肥力，比不施磷肥土壤有机质含量平均提高18.5%，其中NPKM提高30.1%；显著提高土壤微生物生物量，比不施磷肥土壤微生物生物量碳（MBC）平均提高57.2%，其中NPKM提高87.1%；提高氮素、钾素养分利用率，比不施磷肥平均分别提高120.3%、33.6%，其中NPKM分别提高152%、43%。而长期重施无机磷肥处理（NKhP）虽然水稻产量比不施磷肥处理提高125.1%，但因土壤中磷酸根离子含量过高影响土壤微生物正常生长，土壤微生物活度比不施磷处理降低9.4%，土壤微生物量碳（MBC）降低2.4%，稻田土壤微生物生态系统质量劣化。此外，重施磷肥处理（包括NKhP、NKhPM）易导致稻田水体的磷污染。各处理比较，NPKM综合生态效应最佳，以下依次是NKhPM、NPKSi、NPK，NKhP，NKhP对稻田土壤微生物生态系统产生负效应。根据试验结果，平衡施肥是恢复缺磷水稻土的有效措施，其中在平衡施用氮磷钾化肥的基础上增施有机肥或硅肥效果较好。

Ecological effects of balanced fertilization on red earth paddy soil with P-deficiency

In order to study the ecological effect of balanced fertilization on paddy soil with P-deficiency treated, a pot-experiment by cropping rice had been conducted for 3.5 years. The soil for experiment was got from the plowed layer soil in plot treated with chemical N and K but P-fertilizer in a long-term experiment of soil fertility and benefit of fertilizer in red earth paddy soil. Six different treatments including chemical N and K (NK), N, P, and K chemical fertilizer (NPK), N, P, and K chemical fertilizer mixed with Si fertilizer (NPKSi), three-fifths of N, P and K chemical fertilizer and two-fifths of organic manure (NPKM), increasing P chemical fertilizer based on NPK (NKhP), and increasing P chemical fertilizer based on NPKM (NKhPM) were examined. The chemical fertilizer N, P, K, Si for experiment was urea, calcium magnesium phosphate, potassium chloride, and sodium silicate, respectively. The organic manure when cropping early rice was Astragali and pig feces, and when late rice was green straw of rice and pig feces. All fertilizers applied to soil with once application as base fertilizers. When the rice was harvested, soil samples were collected for measuring soil fertility and microbial characteristics; the samples of rice were also collected in the stages of rice maximum tillering, heading, and harvesting, respectively, for the rice biomass and the nutrient quantity; the samples of leaching water were collected after fertilization 1 day, 3 days, 7 days, 15 days, 30 days, 45 days, 60 days and on the day when rice harvested, respectively, for the content of total P. Every treatment was replicated for 6 times. The experiment was carried out in a greenhouse. The cropping system was as rice-rice-fallowing. The indexes of soil fertility, soil microbial characteristics, the content of total P in leaching water, grain yield, nutrient use efficiency and agricultural P fertilizer use efficiency for each treatment were measured/calculated and compared. The results showed that balanced fertilization treatments of NPK, NPKSi, NPKM and NKhPM significantly enhanced the averaged rice yield (147% higher than NK, and NPKM was 152% higher), the indexes of soil fertility (18.5% higher content of organic matter in soil than NK, and NPKM was 30.1% higher), the microbial biomass (57.1% content of MBC higher than NK, and NPKM was 87.1% higher), the nitrogen use efficiency (120.3% higher in IEN than NK, and NPKM was 152% higher), and the potassium use efficiency (33.6% higher than NK, and NPKM was 43% higher). However, although NKhP reached a high rice yield which was 125.1% higher than NK, its soil microbial activity and MBC were 9.4% and 2.4% lower than NK, respectively, mainly due to higher content of phosphate that led the microbe community to grow unhealthy in paddy soil. As results, its quality of paddy soil microbial ecosystem grew worse. Furthermore, excessive application of P-fertilizer (included of NKhP and NKhPM) led to water pollution from phosphorous in rice field. In conclusion, the treatment of NPKM had the best ecological effects under all of treatments, followed by NKhPM, NPKSi, NPK and NKhP that produced negative effect on microbial ecosystem in paddy soil. Accordingly, balanced fertilization was the effective method to restore the paddy soil with P-deficiency, and the treatments of adding organic manure or Si-fertilizer based on balanced application of N, P and K fertilizer had a better effect.