氮肥减量配施生物炭对稻田有机碳矿化及酶活性影响

氮肥减量配施生物炭对于提升土地生产力、提高土壤碳汇能力以及缓解气候变暖具有重要意义。依托大田试验,设置5个氮肥用量梯度(T0～T4):100%化肥氮,90%化肥氮,80%化肥氮,70%化肥氮,60%化肥氮,采用等氮原则,氮肥减少量用等氮量生物炭替代,以不施肥为对照(CK),结合室内矿化培养,揭示稻田有机碳矿化及酶活性对氮肥减量配施生物炭的响应。结果表明:与T0处理相比,T3处理(70%化肥氮+7.5 t/hm~2生物炭氮)土壤全氮,碱解氮及速效磷依次显著提高了6.67%,8.36%及30.94%(P0.05),T4处理的速效钾含量最高,显著提高了23.78%(P0.05)。氮肥减量配施生物炭可有效提升土壤有机碳(SOC)含量,且随配施生物炭比例的增大而增大;与矿化前相比,各处理矿化后SOC,微生物量碳(MBC)及微生物熵(qMB)依次下降1.39～1.75 g/kg, 24.62～67.57 mg/kg及0.13%～0.32%(P0.05)。SOC矿化速率在培养的第1天达到峰值,第1阶段(第1～6天)迅速下降,第2阶段(第6～30天)缓慢下降,第3阶段(第30～45天)矿化速趋于平稳,矿化速率与培养时间呈对数函数关系(P0.01)。培养结束时SOC累积矿化量和累积矿化率的变化范围分别为1.39～1.75 g/kg和6.02%～8.43%,均以T3处理最低。与CK和T0处理相比,T3处理的过氧化氢酶、脲酶和蔗糖酶活性最高,T1处理的酸性磷酸酶活性最高。水稻产量以T3处理(7.37 t/hm~2)最高,比T0处理增产39.58%(P0.05)。综上,氮肥减量30%配施生物炭可明显提高土壤肥力,减少SOC矿化,增加土壤固碳,提高土壤酶活性及水稻产量。

Effects of Nitrogen Reduction Combined with Biochar Application on Organic Carbon Mineralization and Enzyme Activity in Paddy Field

Nitrogen reduction combined with biochar application is of great significance for improving land productivity, improving soil carbon sequestration and mitigating climate warming. Based on the field experiment, five nitrogen fertilizer dosage gradients (T0~T4) were set:The response of organic carbon mineralization and enzyme activity to nitrogen reduction combined with biochar application in paddy fields was revealed by using the principle of isonitrogenous fertilizer (100% N, 90% N, 80% N, 70% N, 60% N). The results showed that compared with T0 treatment, the soil total nitrogen, alkaline hydrolysable nitrogen and available phosphorus in T3 treatment (70% N +7.5 t/hm² biochar nitrogen) were significantly increased by 6.67%, 8.36% and 30.94% (P < 0.05), respectively. The content of available potassium in T4 treatment was the highest and significantly increased by 23.78% (P < 0.05). Soil organic carbon (SOC) content increased with the increase of nitrogen reduction combined with biochar application ratio. Compared with before mineralization, SOC, microbial biomass carbon (MBC) and microbial entropy (qMB) decreased by 1.39~1.75 g/kg, 24.62~67.57 mg/kg and 0.13%~0.32% (P < 0.05) after mineralization. SOC mineralization rate reached the peak value on the first day of culture, decreased rapidly in the first stage (1~6 days), decreased slowly in the second stage (6~30 days), and tended to be stable in the third stage (30~45 days). The relationship between mineralization rate and culture time was logarithmic (P < 0.01). At the end of culture, the SOC cumulative mineralization amount and cumulative mineralization rate varied from 1.39~1.75 g/kg and 6.02%~8.43%, respectively, and T3 treatment was the lowest. Compared with CK and T0 treatments, the activities of catalase, urease and sucrase in T3 treatment were the highest, and the activities of acid phosphatase in T1 treatment were the highest. The highest rice yield was found in T3 treatment (7.37 t/hm²), which was 39.58% higher than that in T0 treatment (P < 0.05). In conclusion, 30% reduction of nitrogen fertilizer combined with biochar can significantly improve soil fertility, reduce SOC mineralization, increase soil carbon sequestration, improve soil enzyme activity and rice yield.