Abstract: In order to improve nitrogen utilization in facility farmland and reduce soil nitrogen accumulation,waxy corn and feeding sweet sorghum was selected as the catch crops,and six different levels of biochar were designed,namely C1(0),C2(0.5%),C3(1%),C4(2%),C5(4%),C6(8%),to study the effects of biochar application on nitrogen uptake by summer crop and soil carbon and nitrogen changes.The results showed that with the increase of biochar application rate,the nitrogen uptake of the two crops first increased and then decreased.Among them,the nitrogen uptake of the aboveground part of the waxy corn C3 treatment was the largest(142.69 kg/ha),feeding sweet sorghum was the best C4 treatment(132.43 kg/ha);the soil total nitrogen decreased by 2.5%-11.0% among different treatments,and the C3 treatment decreased by the most(15.4%),except for C6 treatment, the decrease range of other treatments for feeding sweet sorghum was 1.4% to 15.5%, and the decrease was the most in C3 treatment. After planting feeding sweet sorghum,different treatments and different soil layers had reduced nitrate nitrogen content compared with before planting;The C/N value of the facility soil could be increased by combining different amounts of biochar with catch crops;the application of biochar was beneficial to increase the organic carbon content,the planting of catch crops could reduce the soil urease activity in the early growth period of the subsequent crops,and reduce the nitrogen supply capacity of the subsequent crops during the growth period.With the increase of the application amount of biochar,the soil urease activity increased firstly and then decreased in each treatment.The highest urease activity was 3.33 mg/(g·d) in NC3(preceding waxy corn+C3) treatment after planting for 15 days.After planting for 45 days,the highest urease activity was in TC3(preceding sweet sorghum+C3) treatment,followed by TC2(preceding sweet sorghum+C2) treatment.The combination of biochar application and crop cultivation could increase the soil microbial biomass carbon content at the beginning of the subsequent crop,which was beneficial to the improvement of soil fertility.Under the conditions of this experiment,it was concluded that planting waxy corn with 1%-2% biochar application rate had a better effect on nitrogen absorption,and planting filling feeding sweet sorghum with 0.5%-2% biochar application rate had a better effect on nitrogen absorption,which was beneficial to reduce soil nitrogen accumulation.Planting feeding sweet sorghum has a better effect on reducing soil nitrogen movement than planting waxy corn.

Key words: Catch crops, Facility soil, Soil carbon and nitrogen, Biochar

CLC Number: 

• S158.3