Abstract
A 4-year field trial with three treatments and three types of annually rotated vegetables was conducted in calcareous soil in a greenhouse using a phosphorus (P) fractionation method based on the inorganic P fraction classification system described by Jiang-Gu. With the same nutrient input, vegetable yields and P uptake were more stable under the chemical fertilizer (CF) treatment than under the organic manure (OM) treatment, and the average utilization rate of P fertilizer (URP) values were 5.27% and 11.40% under the OM and CF treatments, respectively, over the 4 years. Compared with the values in 2009, the values of the inorganic P (Pi) fractionation, including Ca-P, Al-P and Fe-P, significantly increased over time by 310.89 mg·kg−1, 36.21 mg·kg−1, and 18.77 mg·kg−1, respectively, with OM treatment and by 86.92 mg·kg−1, 175.87 mg·kg−1, and 24.27 mg·kg−1 with CF treatment. These results suggest that 1) large amounts of P were released from Ca2-P, Ca8-P and Al-P and were taken up by vegetables in the calcareous soil, and 2) the excessive application of P fertilizer, especially OM, resulted in a substantial accumulation of Pi (Ca2-P, Ca8-P and Al-P), which increased the risk of pollution from organic farming diffusing into the surface water.
Highlights
In China, the growing prices of chemical fertilizers (CFs) and the concerns about soil quality have triggered an interest in applying organic manure (OM) to restore fertility
Soil P in non-calcareous soil was divided into different fractions, including Ca-P, Al-P, Fe-P and occluded P (O-P); in calcareous soil, Ca-P was further divided into Ca2-P, Ca8-P and Ca10-P according to the solubility and availability of P8, 9 because the Ca-P content was relatively higher in calcareous than in non-calcareous soil
These studies have reported the accumulation of a large amount of Pi or organic P in the soil due to the continuous application of P fertilizer or OM for many years[10,11,12], but most studies on calcareous soils have been related to wheat, rice or maize[13, 14]
Summary
In China, the growing prices of chemical fertilizers (CFs) and the concerns about soil quality have triggered an interest in applying organic manure (OM) to restore fertility. The effects of CF or OM on P fractionation, inorganic P (Pi) transformation in soil and Pi availability and recovery by crops have been investigated in several studies These studies have reported the accumulation of a large amount of Pi or organic P in the soil due to the continuous application of P fertilizer or OM for many years[10,11,12], but most studies on calcareous soils have been related to wheat, rice or maize[13, 14]. There have been few reports on soil P fractionation and Pi transformation in response to the fertilization of vegetables, especially greenhouse vegetables; the purpose of the current study was as follows: 1) to investigate the response of vegetable yields to different fertilization inputs, such as OM and CF; 2) to evaluate P availability with different fertilization inputs; and 3) to study the transformation of Pi fractions in calcareous soil under excess fertilizer application and vegetable uptake in the greenhouse
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