| Besides its use as an important edible oil and feed crop, rapeseed is also a promising bio-diesel crop. China has been the largest producer of rapeseed with an annual production of more than 10 million tons since 1999. Yangtze River Basin (YRB) is the major rapeseed-growing area in China, and is also the most potential development area of winter rapeseed production in the world. This area contains nearly 6 million hectares of winter rapeseed area, accounting for about 80% of the total areas in China and 20% in the world. Rapeseed yield per unit area in YRB in 2000s increased more than three times compared to that in 1960s. The yield increase during the last decades is not only due to breeding of high-potential cultivars but also to higher nutrient supply. It has an important significance that finds out the yield, quality and economic return of fertilization on rapeseed to popularize and applied the technique of balanced fertilization and ensure a healthy rapeseed industry.With implementation of Soil Testing and Fertilizer Recommendations Action, more and more soil samples were analyzed in laboratories. Fertilizer recommendation can be carried out according to results of soil analyses. Establishment of the critical soil levels was a necessary precondition for fertilizer recommendations from a soil test result. Due to increasing in crop yield levels and soil test laboratory methodology, it is widely recognized that information about soil test critical levels and fertilization recommendation requires updating and revaluation.In this study,74 field experiments were carried out in ten major winter rapeseed-growing provinces of YRB from 2005 to 2007. The aims were:1) to find out the yield, quality and economic return of N, P, K and B fertilization on winter rapeseed; 2) to get to know the situation of nutrient efficiencies and nutrient balance in the agroecosystem of rapeseed production regions; 3) to establish and improve the soil nutrient abundant & deficient indices (based on General test, ASI and M3 methods) and nutrient required characteristic for high-efficient rapeseed production. The main results are summarized below.(1) In this research the soil nutrients content of 272 samples, which were collected from ten main rapeseed planting provinces in Yangtze River Basin, were measured by general test method (GT), a systematic approach (ASI) and Mehlich 3 (M3). The purpose of the study was to find out soil nutrients status and main limiting factors in main rapeseed planting regions. The results showed that soil nutrient for rapeseed-growing in YRB was out of balance, and the great difference existed in soil nutrient content among sample sites. The results of correlation analysis showed that pH and available P, K, Ca, Mg, S, Fe, Mn, Cu and Zn by GT method had significantly positive correlation with those by ASI method at P<0.01 level, while available N and B by GT had no any relationship with those by ASI. Soil avaialbe P, K, Ca, Mg, S and Fe by M3 had significantly positive correlation with those by GT method and avaialbe P, K, Ca, Mg, S, Fe, Cu and Zn by ASI had significantly positive correlation with those by M3 method at P<0.01 level, respectively. The determination results of GT, ASI and M3 method showed that available N, P, K and B concentration of most of soil samples were at deficient or middle level, available S and Zn were at middle level, and available Ca, Mg, Fe, Mn and Cu were at rich level.The results indicated that soil N, P, K and B were the main limiting factors in Yangtze River Basin for rapeseed planting.(2) The combination of N, P, K and B fertilizers significantly increased both rapeseed yield and profits in YRB. The average yield of NPKB treatment was 2654 kg/hm2. Compared with—N,—P,—K and—B, the yield of NPKB was higher by 1133,568,307 and 324 kg/hm2,respectively. The seed yield increment reduced in treatments of P, K, and B application when there were more available P, K, and B in soil. The average profit of NPKB treatment was 7439 RMB Yuan per hectare, which were higher than—N,—P,—K, and—B treatments by 3067,1589,620, and 1028 RMB Yuan per hectare. The effects of N, P, K, and B fertilizer on yield and profit of rapeseed were not identical in all experiments. Based on current facts in agricultural production in China, significant profit was regarded as value to cost ratio (VCR) above 2.0. Among the 74 experiments,89%,78%, and 57% showed significant profit from inputs of N, P, and K fertilizers, respectively. Thus, the technique of combination of N, P, K, and B fertilizers can be popularized and applied in winter rapeseed production in YRB.(3) Balanced fertilization could improve the quality of rapeseed. The effect of N, P, K and B fertilizer on quality of rapeseed were not the same in different experimental sites. N fertilizer had significant influence on oil and protein content, which decreased the content of oil and increased the content of protein in seed. In comparison with N fertilizer, the seed oil content was enhanced due to the application of P, K and B fertilizer. The glucosinolate content and fatty acid composition also had influence on fertilization, but the effect was not significant. The results also indicated that oil content was positively correlated with harvest index and 1000-seed weight, negatively with seed protein content. It was concluded that the combination of P, K and B fertilizer with N could reduced the loss of oil content caused by N fertilizer application.(4) The results of study on nutrient uptake showed that N, K, Ca, Mg, Fe, Mn, Cu and Zn content in the above-ground were decreased gradually with growing time. And the dynamic changes of P, S and B concentration showed an "M" curve. Seed was the distribution center of N, P2O5, MgO, Mn, Cu and Zn, and stem and pod were the distribution center of K2O, CaO, S, Fe and B. The effect of fertilization on N, P, K and B content in pod and stem was stronger than those in seed. The parameters for the QUEFTS (Quantitative Evaluation of the Fertility of Tropical Soils) model in winter rapeseed were aN=13.3, dN=28.5, aP=30.7, dP=85.1, aK=8.7 and dK=28.3. Nutrients required for producing every 100 kg seeds were N 4.7～5.5 kg, P2O51.9～2.7 kg, K2O 6.8～8.7 kg, CaO 6.2～6.4 kg, MgO 1.4-2.0 kg, S 1.8-1.9 kg, Fe 31.8～47.0 g, Mn 7.2～8.3g, Cu 0.9～1.0 g, Zn 6.4～7.7 g and B 4.4～5.4g, and the ratio of N:P2O5:K2O was 1: 0.5～0.6:1.6～1.8. Nutrient requirement of rapeseed was influenced by rapeseed varieties, yield level and nutrient supply. More P and K was required by rapeseed at high yielding level.(5) The results of study on nutrient efficiencies indicated that the average agronomic efficiency (AE) was 6.2 kg/kg N,6.3 kg/kg P2O5 and 2.6 kg/kg K2O, under the experiment condition. Partial factor productivity (PFP) was 14.7 kg/kg N,29.5 kg/kg P2O5 and 22.1 kg/kg K2O. Recovery efficiency (RE) of N, P and K fertilizer were 34.2%, 17.2% and 36.9%, respectively. Physiological efficiency was 20.4 kg/kg N,35.5 kg/kg P2O5 and 9.2 kg/kg K2O. The contribution of N, P and K fertilizer to rapeseed yield were 41.8%,21.0% and 11.4%, respectively. Compared with NPKB, rapeseed yield and fertilizer efficiencies in FFP (farmers’fertilization practice) were lower. AE, RE and PE of N in FFP were 4.1 kg/kg,23.1% and 17.6%, respectively. It was concluded that the combination of N, P, K and B fertilizers significantly increased both rapeseed yield and fertilizer efficiencies.(6) The results of field experiment also indicated N balances in the plots received N fertilizer (NPKB, NKB, NPB and NPK) and P balances in the plots received P fertilizer (NPKB, PKB, NKB and NPK) were both positive when 180 kg N/hm2,90 kg P2O5/hm2,120 kg K2O/hm2 and 7.5 kgborax/hm2 were applied. The combination of N, P, K and B was benefit to reduce N losses and the environmental risk of the pollution. K balances were always negative except in PKB plots, and it is necessary to improve soil K balance by increasing application of inorganic and organic K fertilizer resources.(7) The abundance and deficiency indices for general test method (GT), a systematic approach (ASI) and Mehlich 3 (M3) were determined based on the relationship between crop relative yield and corresponding available soil nutrient values. Compared to the complete treatment, the relative yields of 60%,75%,90% and 95% obtained from the -P,-K and -B treatments were selected to establish the abundance and deficiency indices of soil available P, K and B for winter rapeseed. The extremely deficiency, deficiency, slight deficiency, optimum and abundance indices for soil available P were<6.0,6.0～12.0,12.0～25.0,25.0～30.0 and>30.0 mg P/kg for GT; <5.5,5.5-12.5,12.5～28.5,28.5～38.0 and>38.0 mg P/L for ASI;<8.0,8.0～23.5, 23.5～70.0,70.0～100.0 and>100.0 mg P/kg for M3, respectively. The deficiency, slight deficiency, optimum and abundance indices for soil available K were<60,60～135, 135～180 and>180 mg K/kg for GT;<30,30～75,75～100 and>100 mg K/L for ASI; <50,50～135,135～185 and>185 mg K/kg for M3, respectively. The deficiency, slight deficiency, optimum and abundance indices for soil available B were<0.2,0.2～0.6, 0.6～0.8 and>0.8 mg B/kg for GT; 0.25,0.25～1.0,1.0～1.5 and>1.5 mg B/L for ASI, respectively. The results also showed that the relationship between relative yield in—N plot and soil N test values was not clear. However, the relative yields in—P,—K and—B plots had significantly positive with soil available P, K and B contents. It was concluded that the soil available P, K and B critical indices established using GT, ASI and M3 methods and field experiments can be used as guidance for soil testing and fertilizer recommendation for winter rapeseed production in YRB. |
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