Study On Nutrients Limited Factors And Prescription Fertilization Techniques Of Mulberry Orchards In Hubei

Long history mulberry industry in China occupy an important position in the world. Hubei, the one of most 10 mulberry production provinces is best suitable zone by nationwide agriculture division. Mulberry planting was the base for its industry development. Mulberry leaf is the feed of domestic silkworm. Fertilization directly impacts on the yield and quality of mulberry leaf. The research made use of field investigation, pot experiment, field trials and laboratory analysis. Systematic research was carried on the nutrient status, nutrients diagnose technology and prescription fertilization and nutrition management of mulberry orchards in the main area of silkworm production in Hubei. The main results were summarized as follows:1. The current fertilization situation in the main mulberry orchards in Hubei was investigated and analysed, the major problems in mulberry nutrient management was revealed. The average dosages of nitrogen (N) , phosphorus (P₂O₅) and potassium (K₂O) applied in Mulberry orchards in the Hubei in 2001 were 453.0 kg·hm^-2, 114.0 kg·hm^-2, 175.5kg·hm^-2 respectively, The ratio of N: P₂O₅:K₂O was 1: 0.25: 0.39. Most fertilization times was mainly once(25.0%) or twice(63.6%) in Hubei in a year. The main problems include imbalanced application of N, P and K; lack of moderate and trace element nutrients; improper fertilization period; too few fertilization times etc..2. The type, degree and distribution traits of nutrient hindering factors in main silkworm production area of mulberry orchard in Hubei were revealed. The average level of soil fertility was low, with organic matter 0.95%, available N, P, K being 80.4, 9.71, 87.3 mg·kg^-1 respectively, available Ca, Mg, Cu and Zn being 855 mg·kg^-1, 158.0 mg·kg^-1, 0.80 mg·kg^-1, 0.97mg·kg^-1 respectively. The soil was in severe shortage of available elements such as N, P, K, Ca and Mg while trace elements such as Fe and Cu were either in shortage or excess; that half of the soil in the mulberry orchards lack Zn. 3. The hindering factors and their types and degree in the different main producing area were diagnosed by the soil nutrient systematic approach. The soil nutrient factors in every mulberry orchard lacks degree were as follows:Qichun County N>K>Mg>Ca>P>Zn>B>S;Luotian County N>K>P>Mg=B>S;Macheng County K>N>B>P>Mg;Yuan'an County N>P>Zn>K>Fe>B;Nanzhang County P>N>Fe>Zn>K>B;Yingshan County N>B>K>P>Mg>Ca>Zn.These results were in compliance with the investigation of mulberry orchard soil nutrient in the entire province.4. Field trials indicated that the average increase rate of mulberry leaf yield were 28.7%, 23.8%, 23.5%, 11.1%, 14.2% respectively after applying N, P, K, Ca, Mg fertilizer; The average increase rate of S was 9.4% in eastern Hubei; Applying B in Yuan-an and Nanzhang achieved an increase rate of 3.8% and 5.9% respectively; Applying B obtained an increase rate range of 6.4%～34.6% in eastern part of Hubei; While applying Zn being 9.8% and effect of EDDHA-Fe application was obvious in Hubei. Applying Fe in Yuan'an and Nanzhang obtained an increase of 1965 kg·hm² and 2244 kg·hm² respectively with the increase rates of 8.7% and 11.7%. The N, P coordination experiment indicated that N₄₅₀P₁₅₀ had the highest output; that applying N₄₅₀K₃₀₀ was able to maintain most highest output in each season for The N, P coordination experiment; that applying K with Mg, S, B had even better effects than applying the single nutrient elements with average increasing rate of 46.6%, 43.2%, 44.4% respectively, compared with the control.5. Field test indicated that application of N, K could promote the accumulation quantities of most nutrients in the leaf. The accumulation of N, K, P, Ca, S, Zn and B in the leaf had a positive correlation with the increase of N, K application. N₄₅₀K₃₀₀ had the most biomass. Application of K and B together and K and Mg together improved K content 72.1% and 60.5%.6. Field test also showed that applying the shortage element nutrient which in in the soil could improve leaf quality in general. Employments of N, P, K, S, Mg, B obviously enhanced essential amino acids content and total amount of amino acids in the leaf; application of N, K, S, B enhanced protein content while Mg had little influence; N, Mg, B enhanced entire sugar content, while P, K reduced it and S had little influence; N, P, K enhanced fat content, but S, Mg, B reduced it. 7. Silkworm cocoon quality test showed that applying K on mulberry tree had positive influence on the silkworm cocoon quality. Weight of silkworm, Cocoon reelability percentage, bave length, bave cleanliness increased after applying K. High quantity K had better effect than low one. K₂SO₄ was better than KC1 on increasing silkworm cocoon quality when isometric K was used. Lacking various nutrients could affect silkworm cocoon ultimate output and the sequance was N> P = S> Mg> K>Ca >Zn >B. The cocoon output by using isometric K was only 27.8%-58.5% of OPT processing. In the K foundation increasing N could enhance the silkworm cocoon quality, but applying N without K had negative influence on the reelable cocoon percentage.8. Special Fertilizers formula for mulberry tree was selected in main 3 silkworm production area in Hubei. In the base of fertilization technology study, the optimum fertilizer application technology in mulberry orchards was refined.In the paper, "nutrient management - soil nutrient - mulberry tree nutrient - mulberry leaf output -mulberry leaf quality - silkworm production - silkworm cocoon quality" is systematically researched for the first time; According to novelty search reports, the systematic approach in studying soil nutrient was firstly introduced to diagnose the hindering factors and fertilization effect in mulberry orchard. The type and the degree of barrier factors were confirmed in the main production areas; The effect on mulberry tree in the form of simple substance nutrient, coordination of inorganic nutrient, coordination between organic and inorganic nutrient was systematically studied. 3 special-purpose fertilizer formula for mulberry tree were put forward in view of the 3 main silkworm production areas in Hubei.