Applications of phosphorus and organic fertilizers on yields of vegetables and their environmental impacts

A 5-year in-situ fertilizer experiment in a rotation system of Chinese cabbage–capsicum (bean) was carried out to investigate the influences of excessive application rates of phosphorus (P) and organic fertilizers on vegetables yields, distributions of different P fractions at soil layers of 0–5, 0–10, 10–20 and 20–80 cm, and environmental risk of cumulative P in the field. The Results show that yields of Chinese cabbage, cabbage, capsicum and bean are increased by 21.5%, 39.5%, 71.6% and 50.0% under P2O5 application rates of P2O5180–360 kg /hm2, respectively, while those under manure application rates of 150~300 t/hm2 are increased by 23.8 %, 26.7 %, 62.6 % and 80.0 %, respectively, and the increased yields are all at the significant level comparing to the no fertilizer applications. The response of Chinese cabbage yield to soil Olsen-P at 0–20 cm layer can be modeled using a quadratic equation. After five-year applications of P and organic fertilizers, the contents of different P fractions are enriched at soil layer of 0–60 cm, and the Olsen-P accumulations at 20–40, 40–60 and 60–80 cm soil layers are 35.7%, 11.8% and 7.1% of that at 0–20cm soil layer, respectively. Content of Olsen-P at the 0–20 cm layer is about 88.1% and 84.0% of that at the layers of 0–5 and 0–10 cm, respectively. Soil Olsen-P at 0–20 cm layer is positively correlated to CaCl2-P, NaOH-P and soluble phosphorus in irrigating stayed water and P-index, which indicates that Olsen-P might be a useful indicator to evaluate soil P supply capacity and environmental risk of agricultural P in calcareous soil.