| Determining the amount of livestock manure in farmland is the basis for circular agricultural. This study was based on the facts that the scale of pig-breeding in Chengdu plain is great, and the waste of pigs contains a lot of phosphorus. A field study was conducted to analyze phosphorus accumulation in soil and the changes of phosphorus forms after treated with pig manure in rice-wheat rotation, and to evaluate the security given amount of pig manure in this system considering the risk of phosphorus leaching, yields of rice and wheat and the activity of acid phosphatase in soil. It plays an important role in the resource utilization of pig breeding waste in Chengdu plain and the cyclic utilization agricultural resources.The field study was based on the application amount of conventional phosphatic fertilizer as a standard of applying pig content. The quarterly treatment dosages of N, P2O5 and K2O in rice-wheat rotation were 180 kg·hm-2,75 kg·hm-2 and 90 kg·hm-2, respectively. The treatments were as follows:(Po) No P fertilizer; (P2) Normal fertilizer; (P3) 75% Normal fertilizer +25% swine manure N; (P4) 50% Normal fertilizer +50% swine manure N; (P5) 100% swine manure N; (P6) 150% swine manure N; (P7) 200% swine manure N; With the research on phosphorus accumulation, pattern of inorganic phosphorus, components of organic phosphorus and yield of rice and wheat, the following results were obtained:(1) The concentrations of TP、Olsen-P、CaCl2-P in 0～20 cm soil layer increased significantly with the amount of pig manure increasing. Meanwhile, the concentrations of TP、Olsen-P in 0～20 cm soil layer increased with the growth progress. The concentrations of CaCl2-P in soil at P5 and P6 treatments were significantly higher than that of P1 treatment at each growth period. Furthermore, the concentrations of CaCl2-P in soil ranged from 0.43 to 1.38 mg·kg-1 at P5 and P6 treatments, the ratio of maximum and minimum value reached to 3.21 times. The concentrations of TP and Olsen-P in 0～20 cm soil layer at P3, P4, P5 and P6 treatments were significantly higher than that of P1 treatment after the rice-wheat rotation.The concentrations of TP in 20～40 cm soil layer had no significant difference among the different pig manure treatments. The concentrations of Olsen-P in 20～40 cm soil layer at P5 and P6 treatments were 2.1 mg·kg-1 and 4.7 mg·kg-1 higher than P1 treatment after the rice-wheat rotation, while the concentration of CaCl2-P at P6 treatment was significantly higher than that of Pi treatment.(2) The soil Ca2-P、Al-P、Fe-P、Cas-P content increased significantly with swine applied in the top 20 cm layer of the soil profile, and increased with swine application rates increasing and growth period advancing. The soil Ca2-P、Al-P、Fe-P、Ca8-P、O-P content in P4, P5 and P6 treatment significantly higher than P1 treatment.after a crop rotation.The concentration of them were 69.1,60.9,91.0,96.4 mg·kg-1 higher with treatment P6 than that of P1.The effect on content of O-P was little with swine manure applied, while it had no remarkable influence on Caio-P. The content of Ca2-P、Ca8-P、Al-P、Fe-P were increased significantly with the swine manure application rates increasing.The soil Ca2-P、Ca8-P、 Al-P、Fe-P relative content increased, while the relative content of Caio-P and O-P gradually reduced with the swine manure used,76.45% and 11.32% with P1 declined to 49.40% and 9.25% with P6, respectively.The swine applied have no significant effect on soil Ca8-P、Caio-P、Fe-P、O-P content in the 20～40 cm layer, after a rational soil Ca2-P content in the 20-40 cm layer in P4, P5, P6 treatments were 2.6,5.9,7.1 mg-kg-1 higher than P1, respectively. The content of Al-P with P6 treatment was significant higher than that of Po and Pi.(3) With the application of swine manure, the soil labile organic P (LOP), moderately labile organic P (MLOP), moderately resistant organic P (MROP) and highly resistant organic P (HROP) content increased in the top 20 cm layer. The content of organic phosphorus increased with the application ratio increasing. The soil all organic P content in P5、P6 treatments higher than P1 treatment after one rotation. The soil LOP, MLOP, MROP and HROP content were 1.9,53.1,30.4 and 16.5 mg·kg-1 higher than that of P1, respectively. The LOP, MLOP, MROP and HROP content were significant higher at rice tillering stage than that in mature stage with P4、P5、P6 treatment, while increased after wheat growing season. There was no significant change with P2, P3 treatment. The content of HROP showed a gradually increasing trend with the growth stages advancing. Swine manure had no significant effect on the relative content of each components of organic P in the top 20cm layer.The relative content of each components of organic P was MLOP> MROP> HROP>LOP.Simultaneously, swine manure had no significant effect on soil each components of organic P content, too. After one rotation, the soil LOP content increased to 3.0 mg·kg-1 in P6 treatment and 1.1 mg·kg-1 higher than that of P1 treatment.(4) The critical value of Olsen-P and CaCl2-P were 50.5 mg·kg-1 and 0.70 mg·kg-1 under the rice-wheat rotation cropping system with the application of swine, respectively. Compared with P1, the yield increase rate of P3 was 10.01% and reached the highest yield of 13309.7 kg·hm-2. The Olsen-P and CaCl2-P in 0～20 cm were 19.4 mg·kg-1 and 0.32 mg·kg-1, respectively. The activity of neutral phosphatase was higher than that of P1. There was no influence on the content of various P forms under the treatment P3. Taking the ecological and economic benefit into consideration, the maximum safe capacity of swine manure was 23364 kg·hm-2, and the maximum load capacity of pig(for sale)was 60.2·hm-2·a-1. |
PDF Full Text Request