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 in T1 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 in T1 with organic fertilizer based on 25% mineralization rate (T5), and controlled release fertilizer substitution with the same amount of N in T1 (T6). The garlic field was fertilized four times in the whole growth period. Ammonia volatilization 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 higher than those of other treatments. Ammonia volatilization mainly occurred within 7 days after each fertilization, with the peak value ranging from 2.21 to 9.83 kg/(hm²·d). The cumulative ammonia volatilization varied among the treatments at each fertilization period. The cumulative ammonia volatilization under CF, T1, T2, T3, T4, T5 and T6 treatments were 71.76, 52.3, 30.56, 53.65, 44.67, 59.95 and 40.22 kg/hm², respectively. The loss of ammonia volatilization accounted for 10.63%, 9.48%, 5.50%, 9.72%, 2.02%, 4.80% and 7.30% of the total amount of nitrogen in CF, T1, T2, T3, T4, T5 and T6, respectively. The amount of ammonia volatilization and the loss rate of CF were significantly higher than other treatments, indicating that ammonia volatilization increased with increase in nitrogen application. The order of ammonia volatilization among different treatments was: T2<T4≈T6<T1≈T3<T5.

Conclusions In Erhai Lake Basin, the ammonia volatilization of conventional fertilizer application was significantly higher than other fertilization treatments. There was no significant difference in garlic yields of the fertilizer replacement treatments, but ammonia volatilization and nitrogen loss rate significantly differ. The greater the amount of nitrogen fertilizer, the higher the ammonia volatilization and nitrogen loss rate. Increase in the quantity of organic fertilizer replacement for urea resulted in the increase of ammonia volatilization and nitrogen loss rate. Considering the agronomic and environmental benefits, the single application of organic fertilizer with 20% reduction of the conventional chemical fertilizer rate could enhance garlic yield, reduce ammonia volatilization and replace conventional fertilization practice in Erhai Lake Basin.