施入~(15)N标记氮肥在长期不同培肥土壤的残留及其利用

采用盆栽试验和短期矿化培养相结合的方法,研究了施入15N标记氮肥(+N)及其与秸秆配施(+1/2N+1/2S)在3种长期(19年)不同培肥土壤(即:No-F,长期不施肥土壤;NPK,长期施用NPK化肥土壤;MNPK,长期有机无机肥配施土壤)中的残留及其矿化和作物吸收特性。结果表明,第一季小麦收获后,+1/2N+1/2S处理下三供试土壤和+N处理下的NPK和MNPK土壤残留肥料氮(残留15N)中有82.6%~95.1%以有机态存,而+N处理下No-F土壤残留15N有47.7%以矿质态存在。经过28 d矿化培养后,与NPK土壤相比,MNPK土壤氮素净矿化量显著增加,增幅为39%~49%;NPK和MNPK土壤残留肥料氮(残留15N)矿化量为1.23~1.90 mg kg-1,占总残留15N的2.78%~5.53%,均显著高于No-F土壤。与+N处理相比,+1/2N+1/2S处理显著提高了3供试土壤氮素净矿化量,但两施肥处理对NPK和MNPK土壤残留15N矿化量无显著影响。+N处理下No-F土壤残留15N的利用率为20%,显著高于NPK(9%)和MNPK(12%)土壤。两种施肥处理下,MNPK土壤残留15N的利用率均显著高于NPK土壤。短期培养期间土壤氮素矿化量和第二季小麦生育期作物吸氮量呈显著性正相关,而残留15N矿化量和第二季小麦吸收残留15N量间无显著性相关关系。长期有机无机配施可以提高土壤残留肥料氮的矿化量及有效性。

Residual of applied 15N fertilizer in soils under long-term different patterns of fertilization and its utilization

A pot experiment coupled with short term mineralization incubation were conducted to explore characteristics of residual, mineralization and crop uptake of the ¹⁵N-labeled N fertilizer applied alone and/or together with crop straw in the soils collected from three different treatments of a 19-year fertilizer experiment, i.e. treatment No-F (no fertilization), treatment NPK (long-term NPK fertilization) and treatment MNPK (long-term NPK fertilization plus organic manure). The pot experiment was designed to have two treatments, i.e., treatment +N (100 mg kg^-1 urea-¹⁵N), and treatment +1/2N+1/2S (50 mg kg^-1 urea-¹⁵N + corn stalk equivalent to 50 mg kg^-1N). Fertilizers were added to the pots separately for the first cropping of wheat in 2009. After the first cropping of wheat was harvest, 82.6% ~ 95.1% of the residual fertilizer N in all the three soils under treatment +1/2N+1/2S and NPK soil and MNPK soil under treatment +N were in organic form; and 47.7% of the residual fertilizer N in the No-F soil under treatment +N was in mineral form. After 28 days of incubation for mineralization, the net N mineralization in MNPK soil increased significantly, by 39% ~ 49% over that in NPK soil. In NPK and MNPK soils, 1.23 to 1.90 mg kg^-1 of the residual fertilizer N was mineralized, accounting for 2.78% ~ 5.53% of the total residual fertilizer N in the soils. The net mineralization rate of residual fertilizer N in NPK and MNPK soils was significantly higher than that in No-F soil. Compared to treatment +N, treatment +1/2N+1/2S significantly increased net N mineralization rate in the three soils. However, the two treatments did not affect much the mineralization rate of residual fertilizer N in NPK and MNPK soils. In No-F soil under treatment+N, the residual fertilizer N use efficiency (RNUE) reached 20% in the No-F soilsignificantly higher than that (9%)in NPK and(12%) MNPK soils (p< 0.05). The RNUE in MNPK soil was significantly higher than that in NPK soil regardless of N treatment (i.e., +N, or +1/2N+1/2S). N uptake by the second crop of wheat during the vegetative growing period was found to be significantly and positively related to net soil N mineralization rate during the short incubation period, while no significant correlation was observed between residual fertilizer N mineralization rate and amount of residual fertilizer N absorbed by the second cropping of wheat. To sum up, long-term combined application of organic manure and chemical fertilizer can increase the mineralization rate of residual fertilizer N, and hence improve its bioavailability.