| Vegetable plantation is an important land use type in China.The low nitrogen use efficiency（NUE）and serious nitrogen（N）loss of vegetables,which are a huge obstacle to the sustainable development of agriculture in China.Slow-release fertilizer is a common way to improve NUE.Biochar-based fertilizer（BF）is a kind of slow-release fertilizer with large specific surface area and porous structure.BF has been received great attention because of its advantages of less N loss risk.However,there are few papers about the application of BF in vegetable fields at home and abroad.With the increasing proportion of vegetable fields in the cultivated area,we also need to verify the effectiveness of BF in vegetable fields.In view of this,the field experiment was conducted in a typical vegetable field,located in southeastern China.There were four treatments consisted of control（CK）,conventional fertilizer（CF）,partial substitution of inorganic fertilizer with organic fertilizer（COF）and biochar-based fertilizer（BF）.The effects of new slow-release fertilizer（BF）and other different fertilizer types on NUE of vegetable crops（water spinach,Ipomoea aquatica L.）,N loss and ammonia volatilization of vegetable field were compared and analyzed to verify the potential of carbon-based fertilizer in increasing yield,increasing NUE and reducing nitrogen loss.The main results of this study were as follows:（1）BF treatment had significantly higher yield and NUE.The yields of water spinach in CF,COF and BF treatments were significantly different（p>0.05）,and the yield of BF was significantly higher than that of other treatments.BF had the highest N uptake by water spinach compared with CF and COF treatments,whereas N uptake rates by water spinach for treatments of CF,COF and BF accornted for 27.6%,28.0%,and 40.8%of application N rate,respectively.The AEN and REN of BF treatment were significantly higher than that of CF and COF treatments（p>0.05）.（2）BF and COF treatments can effectively reduce N leaching loss in vegetable field.The rates of inorganic N（NO3--N and NH4+-N）losses via leaching in CF,COF and BF treatments accounted for53.3%,37.7%and 33.4%of application N rate,respectively.The rates of inorganic nitrogen leaching loss of COF and BF were significantly lower than that under the treatment of CF（p<0.05）.The results showed that NO3--N was the main form of N leaching loss in this study.（3）BF treatment promoted ammonia volatilization loss in vegetable field,and COF treatment inhibited ammonia volatilization loss.N losses via ammonia volatilization in CF,COF,and BF treatments accounted for 1.1%,0.8%,and 1.5%of application N rate,respectively.N losses via ammonia volatilization of BF treatment were significantly greater than that of other treatments（p<0.05）,and COF treatment had less N losses via ammonia volatilization compared with CF and BF treatments.（4）According to the analysis of N fate under different fertilizer treatments,N loss in CF,COF,and BF treatments accounted for 1.1%,0.8%,and 1.5%of application N rate,respectively.There was no significant difference among the amount of inorganic N（NO3--N and NH4+-N）residue in the treatments of CF,COF,and BF.N uptake by water spinach was the main N flow direction in BF treatment,which was much larger than other fertilizer treatments.Leaching was the main N loss pathway in fertilizer treatments.Besides,undefined part listed could refer to denitrification losses and non-released N of fertilizer.The higher ratio of undefined part in COF treatment may be attributed,at least in part,to the incomplete decomposition of organic fertilizer.To sum up,under this experimental condition,despite the increasing ammonia volatilization due to the alkalinity of biochar,BF treatment significantly enhanced NUE by increasing N uptake by water spinach and minimized N losses via leaching.This study suggested that BF could serve as a promising slow-release N fertilizer for sustainable N management in field vegetable production. |
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