生物炭-化肥配施对稻田土壤氮磷迁移转化的影响

在控制外源氮输入量相同的前提下,通过设置不同梯度生物炭配施量N1+B0(磷酸氢二铵750 kg·hm~(-2));N_2+B5(磷酸氢二铵583 kg·hm~(-2)+生物炭5000 kg·hm~(-2));N3+B10(磷酸氢二铵416 kg·hm~(-2)+生物炭10 000 kg·hm~(-2));N0+B20(生物炭20 000 kg·hm~(-2))],探讨无机肥减量配施生物炭对土壤氮、磷动态变化的影响。结果表明:4种处理土壤NH_4+-N和TP浓度均呈单峰变化趋势,分别于施肥后第9 d(NH_4+-N)、25 d(TP:N0+B20、N1+B0)和55 d(TP:N_2+B5、N3+B10)达到峰值;N_2+B5和N3+B10处理土壤NO3--N浓度呈双峰变化趋势,于施肥后第10 d和55 d达到峰值,而N0+B20和N1+B0处理土壤NO3--N浓度施肥初期(1～10 d)基本保持稳定状态,之后缓慢下降至稳定水平;N1+B0处理土壤TN浓度在施肥后1～55 d内缓慢下降,此后呈单峰变化趋势,于施肥后第85 d达到峰值;N_2+B5、N3+B10和N0+B20处理土壤TN浓度呈双峰变化趋势,分别于施肥后的第9 d和85 d达到峰值。与单施无机肥N1+B0处理比较,配施生物炭N_2+B5、N3+B10和N0+B20处理土壤TN和TP浓度分别提高了11.1%、33.3%、11.1%和40.0%、40.0%、40.0%,土壤脲酶和磷酸酶活性分别提高了25.0%、30.0%、10.0%和9.76%、18.3%、15.9%,表明生物炭较化肥具有更持久肥效。施肥初期,配施生物炭可提高土壤氮磷比;水稻成熟期,配施生物炭处理田面水氮磷比显著高于单施无机肥处理,能够持续地给水稻提供营养。N3+B10处理下水田面源污染物NO3--N、NH_4+-N、TN和TP的输出负荷分别降低了29.6%、48.1%、49.7%和50.0%,是较适合东北黑土区水田的施肥方式。

Effect of the combined application of biochar and chemical fertilizer on the migration and transformation of nitrogen and phosphorus in paddy soil

The aim of this study is to investigate the effect of the application of a combination of biochar and diammonium phosphate (NH₄)₂HPO₄] on the migration and transformation of nitrogen and phosphorus in paddy soil when the same amount of nitrogen was added. The treatments conducted for this study were N₁+B₀ (NH₄)₂HPO₄ 750 kg·hm^-2], N₂+B₅ (NH₄)₂HPO₄ 583 kg·hm^-2 + biochar 5000 kg·hm^-2], N₃+B₁₀ (NH₄)₂HPO₄ 416 kg·hm^-2 + biochar 10 000 kg·hm^-2], and N₀+B₂₀ (biochar 20 000 kg·hm^-2). The results showed that the concentration of NH₄⁺-N in soil for all four treatments peaked on day 9, and the total phosphorus (TP)concentration peaked on day 25 for the N₀+B₂₀ and N₁+B₀ treatments and on day 55 for the N₂+B₅ and N₃+B₁₀ treatments after fertilization. The concentration of NO₃^--N in soil with the N₂+B₅ and N₃+B₁₀ treatments presented a bimodal variation, peaking on days 10 and 55, whereas that with the N₀+B₂₀ and N₁+B₀ treatments remained steady during the early stages, days 1~10, and then gradually decreased to a stable level. The concentration of total nitrogen (TN)with the N₁+B₀ treatment slowly decreased during days 1~55 after fertilization, and then showed a unimodal trend with a peak value on day 85, whereas that with the N₂+B₅, N₃+B₁₀, and N₀+B₂₀ treatments showed a double-peak trend, peaking on days 9 and 85. Compared with the N₁+B₀ treatment, the concentration of TN and TP, urease and phosphatase activity in soil treated with biochar application treatments of N₂+B₅, N₃+B₁₀, and N₀+B₂₀ increased by 11.1%, 33.3%, 11.1% and 40.0%, 40.0%, 40.0%; 25.0%, 30.0%, 10.0% and 9.76%, 18.3%, 15.9%, respectively, indicating that biochar had a more sustained fertilizer effect than chemical fertilizer alone. At the beginning of fertilization, application of biochar could increase the ratio of nitrogen to phosphorus (N/P)in soil and reduce the outputs of N and P from paddy fields. At the rice maturation stage, biochar application increased the ratio of N/P in the field surface water. The output loads of NO₃^--N, NH₄⁺-N, TN, and TP in surface water with the N₃+B₁₀ treatment decreased by 29.6%, 48.1%, 49.7%, and 50.0%, respectively, in comparison with the N₁+B₀ treatment, indicating that it is a suitable fertilization strategy for paddy fields in the black soil region of Northeast China.