土壤供保氮能力决定稻田氮肥增产效果和利用率

Soil Nitrogen Supply and Retention Capacity Determine the Effect and Utilization Rate of Nitrogen Fertilizer in Paddy Field

黑龙江五常和江苏常熟分属我国东北和华东单季稻区优质粳米的代表性产地,但五常维持水稻高产所需氮肥投入量通常远低于常熟而其增产效果优于常熟。由于两地水热条件、作物品种、农田管理和土壤类型均不同,究竟是何原因导致这种区域差异尚不清楚。为探究土壤因素的影响,在两地稻田分别取黑土型水稻土(BS)和乌栅土(WS),设不施氮(CK)、低氮和高氮(N 150和300 kg·hm^(–2)标记尿素)处理,开展盆栽试验,比较水稻产量、氮肥利用及总损失的土壤差异,并结合室内淹水矿化培养试验,研究两种水稻土氮素矿化特征。结果发现:在相同气候和水稻品种及管理条件下进行的盆栽试验中,各处理水稻产量、氮肥增产效果及地上氮素吸收累积量BS均优于WS,差值法氮肥利用率BS较WS高出20.0~28.7个百分点,然而15 N示踪法氮肥利用率BS却仅较WS高5.56~8.01个百分点。尽管施氮后水稻吸收土壤氮均增加,但BS土壤来源氮增量较WS高95.0%~215%。根据CK和相应施氮处理水稻地上部土壤来源氮差值可计算土壤氮素表观激发量在BS为173~354 mg·pot^(-1),在WS仅为88~113 mg·pot^(-1),与淹水培养试验中施氮后BS土壤矿化氮累积量高出WS 0.95倍~2.49倍相一致。说明施氮对BS土壤供氮量增加有更大促进作用。盆栽试验中BS土壤上15 N肥料总损失也随施氮量增加低于WS。综上,氮肥对BS土壤激发效应强,可提供更多矿化氮和损失较低是其维持较高氮肥利用率和高产的主要原因;而氮肥对WS土壤激发效应低,且肥料氮土壤保持能力较弱,因此,水稻生长对高量氮肥投入的依赖性更高。土壤是影响稻田氮肥增产效果和氮肥利用率差异的重要因素。

【Objective】Wuchang and Changshu are the representative production areas of high-quality japonica single-cropping rice in Northeast and East of China,respectively.However,the amount of nitrogen(N)fertilizer required to maintain a high yield in Wuchang is usually much lower than that in Changshu,but the agronomic use efficiency of fertilizer N(AE)is higher than that in Changshu.Different hydrothermal conditions,crop varieties,farmland managements and soil types in these two places make it difficult to identify what causes such regional differences.To explore soil factors’influence on NUE,black paddy soil(BS)and gleyed paddy soil(WS)were collected from the two rice fields.【Method】There were three N treatments as follows:no N treatment(CK),low N rate and high N rate(N 150 and 300 kg·hm^(–2) with 15 N urea).A rice pot experiment was carried out in Changshu National Agro-Ecosystem Observation and Research Station to compare the rice yield,NUE,and total N loss between the two soils.The characteristics of N mineralization in the two paddy soils were also studied through a three-week indoor anaerobic incubation experiment.【Result】The results suggested that the rice yield,agronomic fertilizer N use efficiency and above-ground N uptake of BS were better than that of WS among these N treatments under the same climate,rice variety and management levels.The NUE of BS was higher than that of WS by about 20.0%–28.7%.However,the 15 N recovery efficiency of BS was only higher than that of WS by about 5.56%–8.01%.Although the above-ground N uptake by rice increased after N addition in two soils,the N increment of BS from the soil source was 95%–215%higher than that of WS.Also,the increment of N taken up from the priming effect(difference of above-ground plant N uptake derived from the soil between CK and the corresponding N application treatments)of BS was 173–354 mg·pot^(-1) and 88^(-1)13 mg·pot^(-1) for WS.This observation was consistent with the results that the soil N mineralization amount of BS was 0.95–2.49 times higher than that of WS after N application in the anaerobic incubation experiment.Thus,this result indicated that the N application had a greater priming effect on the increase of N supply in BS soil.Also,the total loss of 15 N fertilizer in WS soil was significantly higher than that of BS with the increase of N application rate in the pot experiment.【Conclusion】Overall,the high yield and NUE of BS may be related to the fact that N fertilizer could provide a greater priming effect and maintain a higher soil N retention level.However,the rice yield of WS depended more on the N fertilizer input due to its lower priming effect of N fertilizer and had a weaker ability to retain fertilizer N.Thus,the soil is an important factor influencing the difference in agronomic use efficiency of fertilizer N and N use efficiency in paddy fields.