| This paper aimed at the problems, such as vegetables quality decline, the risk of environment pollution risk increasing and so on, which induced by irrational irrigation and excessive fertilizer application during vegetables production. A field experiment was carried out to study the effects of irrigation and organic manure application on yield and quality of vegetables, accumulation and distribution of N, P, K in soils, and heavy metal potential pollution in small rape-caraway-tomato-cucumber rotation system based on the traditional way used by local farmers. Meanwhile, the lysimeter method was used to study the characters of water leakage and nitrate leaching from organic fertilizer in vegetable fields, and the distribution and apparent balance of N in soil-plant systems. The results were as follows:(1) For small rape - caraway - tomato - cucumber rotation system, the content ratio of N/P2O5/K2O was 2.08/1.6/0.7 (t/ha) in conventional fertilization treatment. Gradually, manure application rate affected vegetable yields during cultivation time. Compared with the half conventional fertilizer treatments, the yield had great advantages in conventional fertilizer treatments. There was no significant water and fertilizer effect on yields of small rape and caraway under. The tomato yield in conventional fertilizer treatment was higher than that in half conventional fertilizer treatment, but the difference did not reach significant level. There was a significant effect of fertilizer application rates on cucumber yields. However, the use efficiency of organic fertilizer and economic benefit under conventional water and fertilizer management system were lower than that of the half conventional water and fertilizer management system. The experimental results showed that the input rate of organic manure was excessive under conventional water and fertilizer management, and so the half conventional organic manure input was feasible.(2) In addition to Vc content in vegetables was increasing with the fertilizer application rates, the taste and quality of nutrition under half conventional fertilizer input treatment, such as the lycopene content, soluble protein content, soluble sugar content, soluble solids, sugar and acid ratio and so on, were all superior to conventional water and fertilizer treatment. Excessive use of organic fertilizers resulted in high accumulation of inorganic nitrogen in soils, which was the main cause for over-standard of the nitrate content in vegetables. Half of the fertilizer application decreased nitrate contents in tomato and cucumber. Organic fertilizer application rate impacted on the content of heavy metals in tomato. The contents of heavy metals, such as cadmium (Cd), chromium (Cr), plumbum (Pb), mercury (Hg), arsenic (As), copper (Cu), zinc (Zn), nickel (Ni), increased in tomato, cucumber and soils, there a increasing trend of the contents with the increase of the organic fertilizer application rates.(3) The nutrient inputs far exceeded the crop uptakes in this systems, which resulting in a large number of nutrients accumulating in soils. Both fertilizer application and half conventional fertilization resulted in significant differences of available P and K content in 0-20 cm and 20-40 cm of soil layers, especially for the conventional fertilizer treatment, the accumulation of P and K increased rapidly. The concentration of available P in the conventional fertilizer treatments in the 0-20 cm soil layer was above 400 mg/kg and over 300 kg/ha for available K.(4) Fertilizer application was the main reason that increasing the inorganic N apparent balance. The mainly form of the residual inorganic N in soils was NO3--N. Conventional fertilizer application resulted in a large number of inorganic N accumulating in 0-20cm soil layer. The inorganic N in in conventional irrigation and reduction of irrigation were 430.23 kg/ha and 410.12 kg/ha, and 297.99 kg/ha and 205.96 kg / ha in half conventional fertilizer application, respectively, a significant reduction in residues of inorganic N. A large number of residual inorganic N in soil surface did not transfer to 60cm below soil surface. The inorganic N content in 60cm below soil surface changed slightly. Conventional fertilizer application resulted in inorganic N apparent balance value over 1400 kg/ha in 0-90 cm soils, which will be reduced to 450.49kg/ha in half the amount of fertilizer treatments. Half of fertilizer application can maintain the apparent N balance well under ensuring the N supply.(5) Irrigation is a key factor influencing soil N leaching. In a short period of time, the effects of irrigation on N leaching were greater than fertilizer application. So compared with control fertilizer application treatment, control irrigation was more effective to reduce loss of N leaching. Traditional and half traditional irrigation without fertilizer application resulted N leaching 36.07 kg/ha, 27.05 kg/ha, respectively. The N leaching in traditional irrigation and fertilizer application treatments was 59.8 kg/ha, and was decreased by 14.51, 17.89 and 25.43 kg/ha in half input of fertilizer, 2/3 of traditional irrigation, and the reduction of water and fertilizer treatments. In the traditional irrigation condition, the N leaching loss rates were 1.18% and 0.88% in traditional manure treatment and half traditional manure treatments, respectively. In the half traditional irrigation condition, the N leaching loss rates were 0.74% and 0.8% in traditional manure treatment and half traditional manure treatments.(6) Long-term, a large number of organic manure applications will lead to the accumulation of heavy metals in soils. The content of heavy metals in the organic fertilizer was low in this study, and it had not yet appeared heavy metal pollution in a short period of time.The number of earthworms was the largest in the conventional water and fertilizer management treatment, and was 46 m-2 that higher than other treatments. However, the difference was not significant. |
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