Study On Gross Nitrification-Denitrification And Ammonia Volatilization Losses In Apple Orchard

Barometric Process Separation technique was introduced the basic principles and discussed some aspects in application of this method on upland apple orchard using 9-year-old'Fuji'apple trees. Chemical fertilizers application combined with organic manure was used to monitor ammonia volatilization through a venting method using 18-year-old'Fuji'apple trees. One field experiment was conducted to investigate the effect of dicyandiamide (DCD) and DCD+S on nitrification-inhibiting and ammonia volatilization in apple orchard soil using Barometric Process Separation technique and a venting method. A field and a microplot experiment were combined to study fate of nitrogen under different N application rates in young apple orchard by using two-year-old'Fuji'apple trees. The main results were followed:1. The application of Barometric Process Separation technique on upland apple orchard was studied. The results showed that the sampling depth of soil in 0~21cm is appropriate, taking into account the effects of fertilizer and rhizosphere, avoiding the soil compaction at the same time; The appropriate sampling amount of every T is three, and three replicates; Dynamic of annual variations of gross nitrification rate and denitrification rate was first increase and then decrease.2. The effect of chemical fertilizers application combined with organic manure on ammonia volatilization in spring in apple orchard was studied. The result showed that ammonia volatilization rate and loss amount was dramatically influenced by different fertilization cooperation. There were significant differences in the amount and appeared time about the peak of ammonia volatilization rate among different treatments, the peak appeared time in 100%Y was the earliest, the biggest peak of ammonia volatilization rate(2.07 kg N/(hm2?d)) was in 100%N. The highest gross amount of ammonia volatilization was in 100%N, reaching to 13.46 kg N/hm2, accounted for 4.48% of the N applied and was significantly higher than the values in other treatments; both the gross amount of ammonia volatilization and the proportion of fertilizer application were lowest in 50%N + 50%Y. Our study indicates that combination application of chemical fertilizer and organic manure could lower ammonia volatilization. 3. The effect of dicyandiamide (DCD) and DCD+S on nitrification- inhibiting and ammonia volatilization in apple orchard soil was studied. The results showed that: the NH4+-N in N+DCD and N+DCD+S treatments were higher than N treatment within 40 days after fertilization, N+DCD treatment was significantly higher than N treatment within 6～20 days after fertilization, but N+DCD+S treatment was still significantly higher until 30 days after fertilization, prolonging 10 days than DCD for nitrification inhibition; NO3--N was obviously lower in the two nitrification inhibitor treatments than N treatment, decreased by 18.72%～58.91%. Compared with N treatment, gross nitrification and denitrification rates were lower in N+DCD and N+DCD+S treatments, and the biggest difference appeared at early times, confirmed that nitrification inhibitor can inhibit the transformation of soil NH4+-N to NO3--N effectively. N treatment had the biggest peak of ammonia volatilization rate,but its remaining period was shortest,N+DCD treatment's remaining period was 19 days, and the longest was appeared in N+DCD+S treatment, prolong 17 and 7 days than N and N+DCD treatments. Gross ammonia volatilization rate in treatments with nitrification inhibitor was significantly higher than without, but the %N lost of applied N was in low level in all treatments.4. Fate of nitrogen under different N application rates in young apple orchard by using two-year-old'Fuji'apple trees (M. domestica Borkh. cv. Red Fuji/M. hupenensis Rhed) was studied. The results showed that biomass and N uptake capacity of apple trees increased significantly due to the application of nitrogen fertilizer, but the nitrogen use efficiency (NUE) decreased significantly with increasing of N application rates, NUE of N75, N150 and N225 treatments were 31.28, 22.95 and 19.38%, respectively. With increasing of N application rates, N residual in soil sharply increased, and the majority of residue N concentrated on 0-60cm layer, indicating fertilizer nitrogen losses in deep soil layers were small. The N recovery rate in soil-crop system sharply decreased with nitrogen fertilizer rate meanwhile loss rate increased respectively. The N recovery rate in N75 treatment was 60.41%, which was significantly higher than N150 (46.41%) and N225 (40.88%) treatments; while the loss rate in N75 treatment was the lowest (39.59%), and was significantly lower than the other two treatments. Amount of ammonia volatilization increased significantly with increasing of N application rates, but no difference in N2O loss, and the proportion of ammonia volatilization and N2O loses in nitrogen loses was very low, and more nitrogen may lose through denitrification and runoff.