Study On Characteristics Of Nitrogen Mineralization In Green Manuring Tobacco Planting Soils

Green manure application can not only improve soil fertility, but also can improve the quality of flue-cured tobacco.But improper green manuring period, green manuring amount and nitrogen application rate will affect the soil nitrogen supplying capacity and flue-cured tobacco growth. Using incubation experiment and field situ cultivation experiment under controlled temperature, soil moisture and nitrogen application rate, the general objective of the paper was to study the characteristics of nitrogen mineralization in green manuring tobacco planting soils.The study includes 1) The effect of temperature on nitrogen mineralization in green manuring tobacco planting soils; 2) The effect of soil moisture on nitrogen mineralization in green manuring tobacco planting soils; 3) The effect of nitrogen application rate on nitrogen mineralization in green manuring tobacco planting soils; The experiment using green manure either with (G2) or without green manure (G1) or together with urea-N (0(N1),50(N2), 100(N3),150(N4) mg N kg^-1soil) at various levels of soil moisture (20%, 40% and 60% of the maximum field capacity ) and temperature (10,20 and 30℃) were carried out for 56 days incubation. Field in situ cultivation experiment, including Green Manure (G1) and without green manure (G0) with four levels of nitrogen application rate (0 mgN kg^-1 soil (N₁), 50 mgN kg^-1 soil (N₂), 100 mg N kg^-1 Soil (N₃), 150 mg N kg^-1 soil (N₄)): G₀N₁, G₀N₂, G₀N₃, G₀N₄ and G₁N₁, G₁N₂, G₁N₃, G₁N₄. The main results were as follows:1. Green manure increased the effect of temperature, soil moisture and nitrogen application rate on soil nitrogen mineralization, on Green Manure mineralization of soil N after the maximum temperature was the most influential factors in green manuring Tobacco Planting Soil, followed by soil moisture, and finally the nitrogen application rate. The accumulation of soil inorganic nitrogen was based on ammonium nitrogen in prophase, and nitrate nitrogen in later period in green manuring tobacco planting soils. On the one hand, green manuring increased soil organic matter, soil total nitrogen, soil microbial biomass, soil nitrate nitrogen and ammonium nitrogen, and accelerated the mineralization of soil nitrogen, increasing the accumulation of soil net N mineralization. On the other hand, green manure consumed soil nitrate and ammonium nitrogen, and more ammonium nitrogen than nitrate nitrogen. Under field conditions, most of the green manure was decomposed within 40d, decomposed completely within 60d almost.2. The soil moisture was proportional to the nitrate nitrogen, ammonium nitrogen, inorganic nitrogen and soil net mineralization nitrogen accumulation cultivated under 20℃and 30℃. It's more limited to nitrate nitrogen than ammonium nitrogen when the soil moisture is 20% of the maximum field capacity. Low soil water put off the soil mineral nitrogen peak. Neither 60% nor 20% of the maximum field capacity was conducive to the continued accumulation of soil mineral nitrogen within 7 days after green manuring. Although the soil moisture was proportional to the soil mineral nitrogen after 7 days, 60% of the maximum field capacity was not conducive to the continuous accumulation of net mineral nitrogen in soil. 3. Varying nitrogen application rate failed to alter the dynamic curve trends of nitrate nitrogen, ammonium nitrogen, inorganic nitrogen and net mineral nitrogen accumulation in the soil; Overall, nitrogen application rate was proportional to the nitrate nitrogen, ammonium nitrogen, inorganic nitrogen and total nitrogen in the soil. The high nitrogen application rate was not conducive to the accumulation of net mineral nitrogen in soil cultivated under 10℃and 20℃, and the effects of temperature, soil moisture and nitrogen application rate on net mineral nitrogen accumulation in the soil interacted .