Phosphorus (P) leaching is a major problem in greenhouse vegetable production with excessive P fertilizer application.  Substitution of inorganic P fertilizer with organic fertilizer is considered a potential strategy to reduce leaching, but the effect of organic material addition on soil P transformation and leaching loss remains unclear.  The X-ray absorption near-edge structure (XANES) spectroscopy technique can determine P speciation at the molecular level.  Here, we integrated XANES and chemical methods to explore P speciation and transformation in a 10-year field experiment with four treatments: 100% chemical fertilizer (4CN), 50% chemical N and 50% manure N (2CN+2MN), 50% chemical N and 50% straw N (2CN+2SN), and 50% chemical N and 25% manure N plus 25% straw N (2CN+2MSN).  Compared with the 4CN treatment, the organic substitution treatments increased the content of labile P by 13.7–54.2% in the 0–40 cm soil layers, with newberyite and brushite being the main constituents of the labile P.  Organic substitution treatments decreased the stable P content; hydroxyapatite was the main species and showed an increasing trend with increasing soil depth.  Straw addition (2CN+2SN and 2CN+2MSN) resulted in a higher moderately labile P content and a lower labile P content in the subsoil (60–100 cm).  Moreover, straw addition significantly reduced the concentrations and amounts of total P, dissolved inorganic P (DIP), and particulate P in leachate.  DIP was the main form transferred by leaching and co-migrated with dissolved organic carbon.  Partial least squares path modeling revealed that straw addition decreased P leaching by decreasing labile P and increasing moderately labile P in the subsoil.  Overall, straw addition is beneficial for developing sustainable P management strategies due to increasing labile P in the upper soil layer for the utilization of plants, and decreasing P migration and leaching.

Organic manure application is an important measure for high yield and good quality vegetable production, whereas organic manure is also a main source of residual antibiotic in soils. A 3-yr experiment was conducted on a fluvo-aguic soil in Tianjin of northern China. The objective of this study was to investigate the effects of different fertilization patterns on yield of six-season vegetables with celery and tomato rotation, and dynamic change of tetracyclines residues in the soil during the sixth growing season (tomato season). The field experiment comprised six treatments depending on the proportion of nitrogen of each type of fertilizer: 4/4 CN (CN, nitrogen in chemical fertilizer), 3/4 CN+1/4 MN (MN, nitrogen in pig manure), 2/4 CN+2/4 MN, 1/4 CN+3/4 MN, 2/4 CN+1/4 MN+1/4 SN (SN, nitrogen in corn straw), and CF (conventional fertilization, the amounts of nitrogen application were 943 and 912 kg N ha–1 for celery and tomato season, respectively). In addition to CF treatment, the amount of nitrogen application in other treatments was greatly reduced and equal (450 and 450 kg N ha–1 for celery and tomato season, respectively). Results showed that the combined application of 3/4 CN+1/4 MN achieved the highest yield and economic benefit in the first four seasons, but addition of straw (2/4 CN+1/4 MN+1/4 SN treatment) performed better in the subsequent two seasons, and the average yields of 2/4 CN+1/4 MN+1/4 SN treatment were respectively higher by 9.9 and 12.8% than those of 4/4 CN treatment, and by 5.6 and 10.5% than those of CF treatment. The residual chlortetracycline (CTC) in manure-amended soil for three consecutive years increased along with the increase of applied amount of pig manure. Under the same amount of pig manure application, content of CTC in straw-amended soil was obviously decreased compared with no straw-amended soil (3/4 CN+1/4 MN treatment), and averagely decreased by 41.9% for four sampling periods in the sixth season. Addition of crop straw facilitated the degradation of CTC in manure-amended soil. As a whole, the conventional fertilization was not the desirable pattern based on yield, economic benefit and environment, the optimal fertilization pattern with the highest yield and profit and the least soil chlortetracycline residue was the treatment of 2/4 CN+1/4 MN+1/4 SN under this experimental condition.