长期有机培肥提高红壤性水稻土生物学特性及水稻产量的微生物学机制

  【目的】  依托位于江西红壤研究所的有机肥长期定位试验，探究长期施用紫云英、猪粪和秸秆还田对土壤微生物量、酶活性和产量的影响，阐明土壤微生物学特性对土壤肥力的生物指示功能，揭示影响作物产量和微生物学特性的关键环境因子。  【方法】  长期定位试验始于1981年，选取的6个处理分别为:CK (不施肥)、NPK (单施化肥)、M1 (早稻施绿肥)、M2 (早稻加倍施绿肥)、M3 (早稻施绿肥+晚稻施猪粪) 和M4 (早稻施绿肥+晚稻秸秆还田)，此外，有机处理 (M1、M2、M3和M4) 在施用有机物料的基础上，每季还补充一定量化肥（N 69 kg/hm2、P₂O₅ 30 kg/hm2、K₂O 67.5 kg/hm2）。于每季收获后测定水稻产量。2018 年早稻收获后，采集耕层 (0—20 cm)土壤，测定土壤化学指标、微生物量碳氮、脲酶及其他参与土壤碳、氮、磷和硫循环的胞外酶活性。  【结果】  1) 2009—2018年间，长期施肥处理明显提高了水稻产量，其中M3处理的产量最高，其次为M2处理，二者均明显高于NPK处理；2) 土壤微生物量及酶活性均以有机处理 (M1、M2、M3和M4) 较高，其中M3处理土壤微生物量碳含量及各类土壤酶活性最高，M2处理土壤微生物量氮含量最高。有机处理较CK和NPK处理提高了土壤微生物熵。此外，微生物量碳氮和土壤酶活性与有机碳、全氮间存在显著或极显著相关关系；3) 有机碳与土壤微生物量 (0.895)、碳循环相关酶活性 (0.903)、氮循环相关酶活性 (0.854) 及水稻产量 (0.827) 呈显著正影响 (P < 0.05)；土壤pH与土壤碳循环相关酶活性 (0.378) 和氮循环相关酶活性 (0.365) 呈显著正影响 (P < 0.05)，对水稻产量 (0.211) 也表现为正影响，但不显著 (P > 0.05)。相较于pH，土壤有机碳含量在提高水稻产量、改善土壤微生物学特性上发挥了更为重要的作用。  【结论】  土壤微生物量碳氮和参与土壤碳、氮、磷和硫循环的胞外酶活性均可作为土壤微生物学指标表征土壤肥力的变化。土壤有机碳含量是提高作物产量、调控土壤微生物量和酶活性的关键因子。在供试条件下，长期实行早稻施绿肥+晚稻施猪粪的有机培肥，是提高土壤微生物量及酶活性并提高水稻产量的最佳选择。

Microbiological mechanism of long-term organic fertilization on improving soil biological properties and double rice yields in red paddy soil

  【Objectives】  Based on the long-term organic fertilizer experiment set in Jiangxi Institute of Red Soil, the effects of long-term different fertilization on soil microbial biomass carbon, microbial biomass nitrogen, enzyme activities and rice yield were evaluated, the function of these soil microbiological properties as bio-indicators of soil fertilization was illustrated, and the key factor of improving yield and soil microbiological properties was explored in red paddy soil by applicating green manure, pig manure and straw.  【Methods】  The long-term experiment was established in 1981. In the present study, six fertilization treatments were selected: CK (no fertilizer), NPK (chemical NPK fertilizers), M1 (green manure merely at early rice), M2 (double M1 rate at early rice), M3 (M1 at early rice and pig manure at late rice), M4 (M1 at early rice and straw returning at late rice). In addition, a certain amount of fertilizer (N 69 kg/hm2, P₂O₅ 30 kg/hm2, K₂O 67.5 kg/hm2) was applied to the organic treatments (M1, M2, M3 and M4) every season on the basis of the application of organic materials. Rice yield were investigated after each harvest. After harvesting early rice in 2018, topsoil (0–20 cm) sample was collected and soil chemical properties, soil microbial biomass carbon and nitrogen contents, urease and other soil extracellular enzyme activities involved in soil carbon, nitrogen, phosphorus and sulfur cycles were measured.  【Results】  Long-term fertilization increased rice yield from 2009 to 2018, with the highest yields in M3 and followed by M2, and those in both of them were obviously higher than that in NPK. Soil microbial biomass and enzyme activities were both higher in organic treatments (M1, M2, M3 and M4), among which the soil microbial biomass carbon and enzyme activities in M3 were the highest, and the soil microbial nitrogen in M2 was the highest. The microbial quotients in organic amendments were higher than those in NPK and CK. Furthermore, there was significant positive relationship between soil microbiological properties and soil organic carbon, total nitrate and available phosphorus; 3) Soil organic carbon played a more profound influence than pH on increasing crop yield, soil microbial biomass and enzyme activities.  【Conclusions】  Soil microbial carbon and nitrogen, enzymes activities can be bio-indicators reflecting the changes of soil fertilization. Soil organic carbon is the key factor of regulating soil microbiological properties and rice yield. Under the experimental condition, returning green manure at early rice and pig manure at late rice has been proved of the most efficient organic fertilization in increasing soil microbial biomass, enzyme activities and rice yields of the double rice system.