施肥对云南洱海流域蒜田土壤氨挥发和大蒜产量的影响

  【目的】  探究不同施肥措施及施氮量对大蒜产量的影响以及蒜田的氨挥发排放特点，实现在保证效益的前提下的最小环境代价。  【方法】  田间试验在云南省大理市进行，试验设不施肥 (CK)；常规施肥 (N、P₂O₅、K₂O分别为675、180、150 kg/hm2，CF)；减少20%的CF处理化肥用量 (N、P₂O₅、K₂O分别为540、144、120 kg/hm2，T1)；T2处理是将 T1 处理中的氮以有机肥替代；T3处理是将T1 处理中的磷以有机肥替代；T4处理是按有机肥当季矿化率 25% 折算，以有机肥替代 T1 处理中的氮投入； T5处理是按有机肥当季矿化率 25% 折算，以有机肥替代 T1 处理中的磷投入；T6处理是以控释肥替代 T1 处理中的化肥氮，共8个处理。T2和T4处理为单施有机肥，总氮投入量分别为540和2160 kg/hm2；T3和T5处理为有机无机肥配合，总氮投入量分别为540和1224 kg/hm2。每季大蒜施肥4次，每次施肥后，采用密闭室间歇通气法吸收、分析田间氨挥发排放量，在收获期对大蒜进行测产。  【结果】  CF处理的大蒜产量最高，且显著高于其他所有处理，除对照外，其他6个处理的大蒜产量之间没有显著差异。蒜田氨挥发主要发生在每次施肥后的7 天内，整个生育期氨挥发速率峰值变化范围为2.21～9.83 kg/(hm2·d)。不同时期氨挥发累积排放量也存在差异，基肥期氨挥发损失量为4.93～27.77 kg/hm2，第1次追肥损失量为3.24～19.55 kg/hm2，第2次追肥损失量为2.80～18.57 kg/hm2，第3次追肥损失量为3.60～15.29 kg/hm2。CF、T1、T2、T3、T4、T5和T6处理的氨挥发累积量分别为71.76、52.30、30.56、53.65、44.67、59.95和40.22 kg/hm2，氨挥发损失分别占施氮量的10.63%、9.48%、5.50%、9.72%、2.02%、4.80% 和7.30%。CF处理的氨挥发量和氨挥发损失比例明显高于其他6个处理；在其他6个处理中，氨挥发量的顺序为T2 < T4 ≈ T6 < T1 ≈ T3 < T5 (P < 0.05)。  【结论】  洱海地区常规施肥获得的大蒜产量显著高于减量和有机肥替代施肥模式，但其氨挥发量和损失率也明显高于其他模式。T1～T6处理中，大蒜产量没有显著差异，但是氨挥发量和损失率却不同。有机肥施用量大也会显著增加氨挥发量和氮损失率，在高量有机肥中配合尿素显著增加了氨挥发量和氮素损失率。因此，氮素施用量决定着氨挥发损失量。综合考虑农学和环境效益，在洱海流域，减少常规氮肥用量的20%，并以有机肥氮替代全部化肥氮为适宜的施肥方式。

Effects of fertilization on ammonia volatilization and garlic yield in Erhai Lake Basin of Yunnan Province

Objectives]We assessed the effects of fertilizer types and nitrogen application rates on ammonia volatilization and garlic yield.Methods]In November 2018,we established a garlic field experiment with different fertilization strategies in Erhai Lake Basin,Dali,Yunnan Province.The eight fertilization treatments in the study included:no fertilization(CK),conventional fertilizer rate(N–P₂O₅–K₂O 675–180–150 kg/hm²,CF),20%reduction of conventional fertilizer rate(N–P₂O₅–K₂O 540–144–120 kg/hm²,T1),replacement of N inT1 with same amount of organic fertilizer(T2),replacement of P in T1 with same amount of organic fertilizer(T3),replacement of N in T1 with organic fertilizer based on 25%mineralization rate(T4),replacement of P inT1 with organic fertilizer based on 25%mineralization rate(T5),and controlled release fertilizer substitution withthe same amount of N in T1(T6).The garlic field was fertilized four times in the whole growth period.Ammoniavolatilization were monitored using the method of closed chamber intermittent ventilation after each fertilization,and garlic yield was measured during harvest period.Results]The garlic yield of CF was significantly higherthan those of other treatments.Ammonia volatilization mainly occurred within 7 days after each fertilization,withthe peak value ranging from 2.21 to 9.83 kg/(hm²·d).The cumulative ammonia volatilization varied among thetreatments at each fertilization period.The cumulative ammonia volatilization under CF,T1,T2,T3,T4,T5 andT6 treatments were 71.76,52.3,30.56,53.65,44.67,59.95 and 40.22 kg/hm²,respectively.The loss of ammoniavolatilization accounted for 10.63%,9.48%,5.50%,9.72%,2.02%,4.80%and 7.30%of the total amount ofnitrogen in CF,T1,T2,T3,T4,T5 and T6,respectively.The amount of ammonia volatilization and the loss rate ofCF were significantly higher than other treatments,indicating that ammonia volatilization increased with increase innitrogen application.The order of ammonia volatilization among different treatment swas:T2