Study on Characteristics of Decomposition and Nutrients Release of Two Kinds of Green Manure Crops

With nylon mesh bags, the decomposition and nutrients release characteristics of two kinds of green manure crops, February orchid （Orychophragmus violaceus） and Hair Vetch （Vicia villosa Roth）, were investigated in this study. The results showed that these two kinds of green manure crops were decomposed rapidly in the first 14 days, and then decomposed slowly. After 80 days of incubation, the decomposition rates of February orchid and Hair Vetch were 66.92% and 63.12%, respectively. Different nutrients had different release rates from the green manures. Nitrogen （N） and potassium （K） were released rapidly in the initial 7 days, and phosphorus （P） was released steadily in the 80 days of incubation. In the two kinds of green manures, the release rates all ranked as K＇s〉N＇s〉P＇s. The release rates of nutrients, especially P （P〈0.05）, of February orchid were higher than those of Hair Vetch.

Nutrient Release Characteristics of Vinyl Chloride-Vinyl acetate Copolymers Coated SlowRelease Nitrogen Fertilizer and Its Effect on Soil Mineral Nitrogen

[Objective] The aim was to explore release characteristics of vinyl chlo- ride-vinyl acetate copolymer controlled-release N fertilizer and the effects on minerat nitrogen in soils. [Method] Vinyl chloride-vinyl acetate copolymer and hydroxyl-modi- fied VCNAc were taken as coating materials to prepare slow release fertilizer. Nutri- ent release characteristics of VC/VAc slow release fertilizer was evaluated by water immersion method and the effects of VC/VAc slow release fertilizer on mineral ni- trogen were researched by pot experiment. [Result] The release periods of VC-VAc controlled-release urea and hydroxyl-modified VC/VAc coated urea were 60 and 50 d, respectively. Furthermore, the content of ammonium nitrogen reached the peak on the 30th d and the content of nitrate nitrogen reached the peak on the 60th d in soils in treatments with VCNAc and hydroxyl-modified VC/VAc; the content of nitrate nitrogen rose again on the 120th d in the treatment with VC/VAc. In terms of wheat yield, different treatments showed insignificant differences and rice yield in the treatment with VCNAc was significantly higher than that in the treatment with hy- droxyl-modified VCNAc （P〈0.05）. [Conclusion] The release days of slow controlled- release fertilizer vary upon pot experiment method and water immersion method. Slow controlled-release fertilizer is not suitable for monoculture, due to long fertilizer efficiency, but multiple cropping would be optimal for its role to be fully exploited.

Study on Soil Nutrient Contents and Nutrient Characteristics of Ginger(Zingiber officinale Rosc.)

[Objective] This study was conducted to provide scientific basis for fertilization of ginger with high quality and high yield. [Method] The soil nutrient contents and plant nutrient characteristics of Zhugen ginger（Zingiber officinale Rosc.） were studied. [Result] The results showed that： the soil of ginger planting area in Chongqing（Yongchuan） Seedlings of science and technology city was acidic overall,the soil organic matter content was low and alkali-hydrolyzable N was at moderate level; and the contents of available P, Ca, Mg, Fe, Mn, Cu and Zn were extremely rich, while the available S was in lack. The contents of N and K were abundant and P was little in ginger plants, the content of K was more than N in ginger roots and stems, while the content of N was more than K in ginger leaves. [Conclusion]In practical production, it was necessary to fertilize rationally and control the ratio of N fertilizer to K fertilizer according to local conditions, thereby promoting ginger growth and realize high-yield ginger production.

The Production of Organic-Inorganic Compound Film-Coated Urea and the Characteristics of Its Nutrient Release

The effect of different concentrations of natural macromolecular compound on the characteristics of nutrient release in the membrane materials of organic-inorganic compound film-coated urea was discussed, and the optimal concentrations for better nutrient release was proposed. The characteristics of nutrient release of film-coated urea were evaluated by soil column leaching experiment. Organic-inorganic compound film-coated urea showed good characteristics of nutrient release, which could be well simulated by Logistic curve. The two parameters in this curve, a and r, can be used to present nutrient release of film-coated urea, and followed the order of B 〉 C 〉 A and C 〈 B 〈 A, respectively, indicating that the release was stronger with the increasing concentration of natural macromolecular compound in the membrane, which implied better controllability of nutrient release. The concentration of 5% of natural macromolecular compound showed better characteristic of nutrient release and can be utilized as a membrane material combined with inorganic mineral powders to develop film-coated slow-release fertilizer.

Spatial characters of nutrients in Wujiangdu Reservoir in karst river,SW China

A preliminary assessment of the Wujiangdu Reservoir examined nutrient distribution and transport.Water samples were collected in the summer(July) of 2004, during the high-flow season. Inorganic nutrients(N,P, Si) and chlorophyll a(chl a) concentrations of the Wujiangdu Reservoir and its inflow rivers were analyzed.Other water parameters(dissolved oxygen, p H, temperature, and electrical conductivity) were measured as well.The results show gradually decreasing concentrations of NO_3^--N and dissolved silicate in the surface water moving downstream to the dam of the Wujiangdu Reservoir.Additionally, soluble reactive phosphorus concentrations measured very low, with most falling below the sensitivity threshold of the method used in surface waters. Particulate phosphorus and NO_3^--N were the predominant species of phosphorus and nitrogen in the reservoir, respectively. The concentration of nutrients in the Yeji River was the largest of all inflow rivers. The maximum concentration of chl a was found near the dam. These results reflect upstream conditions similar to that of a river, and reservoir conditions near the dam similar to that of a natural lake system.

General Situation of Green Manure Germplasm Resources in China and Research Progress on Decomposition Characteristics and Fertility Improvement of Green Manures

As a kind of biological fertilizer sources, green manure can improve soil fertility and the quality of agricultural products. This paper introduced the germplasm resource of green manures in the major provinces in China, mainly summarized the characteristics of decomposition and nutrients release of returning green manures to soils, as well as the influence on soil fertility and succeeding crops, with the aim to provide references for rational utilization of green manures and the scientific management of farmland nutrients.

Effects of different phosphorus concentrations and N/P ratios on the growth and photosynthetic characteristics of Skeletonema costatum and Prorocentrum donghaiense

The effects of different phosphorus(P) concentrations(0.36, 3.6, and 36 μmol/L corresponding to low-, middle-, and high-P concentration groups, respectively) and nitrogen(N)/P ratios on the growth and photosynthetic characteristics of S keletonema costatum and Prorocentrum donghaiense were studied. For both species, the high-P(HP) concentration group showed the greatest algal density and highest specifi c growth rate. Changes in the maximum effi ciency of photosystem Ⅱ(F _v/F_m) were monitored under the various P and N/P conditions. The largest decrease in F _v/F_m was in the low-P(LP) group in S. costatum and in the HP group in P. donghaiense. There were high rapid light curves and photochemical quantum yields(Φ _(PSⅡ)) for S. costatum in the HP group, while the actual photosynthetic capacity was higher in P. donghaiense than in S. costatum in the MP group. Under eutrophic but relatively P-restricted conditions, P. donghaiense had higher photosynthetic activity and potential, which could cause this dinofl agellate to increasingly dominate the phytoplankton community in these conditions. Under the same P concentration and N/P ratio, P. donghaiense had a larger relative maximum rate of electron transport and higher Φ _(PSⅡ) values than those of S. costatum. These differences between P. donghaiense and S. costatum may explain the interaction and succession patterns of these two species in the Changjiang(Yangtze) River estuary from a photosynthesis perspective.