Effects of organic manures on dynamic changes of nitrate contents of soil profile in greenhouse

A field plot experiment was conducted to study the effects of different organic manures on greenhouse soil NO3--N accumulation, distribution and seasonal changes. The results show that the impacts on greenhouse soil NO3--N are varied with seasons under the application of the organic manures. In summer, high levels of the organic manure applications lead to NO3--N accumulation in soil and vegetables, and promote the NO3--N migration to the lower soil depths. On the contrary, high levels of organic manures reduce the NO3--N contents of soil and vegetables, and reduce NO3--N migration to the subsoil in winter. Take the treatment of swine manure with 22.5 t/ha as an example, in 0-10 cm, 0-80 cm soil depth and tomato, the accumulation of NO3--N are increased by 56.69%, 31.48% and 23.94%, respectively, compared with the chemical fertilizer treatment, in summer. But in winter, the accumulation of NO3--N are reduced by 67.38%, 61.74% and 6.26%, in 0-10 cm, 0-80 cm soil depth and edible celery parts, respectively. Different treatments have different magnitudes of annual variations of soil nitrate. The order from high to low is chicken manure swine manure commercial organic fertilizer chemical fertilizer. Therefore, the application amounts of organic manures should be different in different seasons. The vegetable harvested in summer should be appropriate to reduce the application amount. On the contrary, the vegetable harvested in winter could be appropriate to increase the application amount.