稻鸭共作生态系统稻田土壤固定态铵含量及有效性

The dynamics and availability of soil fixed ammonium in rice-duck complex ecosystems

通过田间试验研究了稻鸭共作生态系统土壤固定态铵的动态及有效性和温度、土壤pH、土壤交换性铵及土壤质地对土壤固定态铵的影响。研究结果表明：（1）在水稻生育期间，土壤固定态铵含量处于不断变化之中，施肥促进土壤对铵的固定，水稻的吸收促进土壤固定态铵的释放；其中在固定态铵释放过程之中，新固定的肥料铵几乎完全释放，而原有固定态铵没有释放。（2）较之常规稻作，稻鸭共作显著地提高了土壤固定态铵含量，其平均含量高出常规稻作的7％。（3）土壤交换性NH；含量和pH与土壤固定态铵含量呈显著正相关（p〈0．01）；土壤温度（5cm土层）与土壤固定态铵含量间不相关；土壤固定态铵含量与〉0．2mm的砂粒含量和〈0．002mm的粘粒含量呈显著或极显著相关，而与0．02-0．2mm和0．002-0．02mm粘粒含量不相关。

Field experiments on dynamics and availability of soil fixed ammonium in rice-duck ecosystems and its influencing factors were conducted from May to September in 2007. The results showed that during rice growth fixed ammonium changed constantly in paddy soils, and application of fertilizer could promote fixation of ammonium while rice growth boosted the release of fixed ammonium. Further, during rice growth, recently fixed ammonium was almost completely released, while native fixed ammonium was not released. Compared to conventional rice field （CK） , rice-duck complex ecosystem （RD） could significantly increase fixed ammonium content; moreover, the mean content of fixed ammonium in RD was （ 103.25±19.15 ） mg/kg, 7% higher than that in CK. Close correlations existed between soil exchangeable NH4, pH and fixed ammonium at the significant differences of 1% level. Soil temperature （at 5cm depth） was not associated with soil fixed ammonium. Soil fixed ammonium was positively related to 〉 0.2mm sand at the significant differences of 5% and negatively related to 〈 0.002mm clay at the significant differences of 1% level, and not associated with 0.02-0.2mm and 0.002-0.02mm particles.