Biomass production and root distribution of Gmelina arborea under an agrisilviculture system in subhumid tropics of Central India

A study of an agrisilviculture system comprising Gmelina arborea and soybean (Glycine max) was conducted in the subhumid region of Central India. Above- and below-ground biomass production and distribution of coarse and fine roots were studied in 4-year-old G. arborea, planted at a spacing of 2 × 2 m, 2 × 3 m, 2 × 4 m and 2 × 5 m. The total biomass varied from 10.89 Mg ha^–1 to 3.65 Mg ha^–1 depending on the tree density. Among the different tree components, stemwood contributed maximum biomass (54.3–79.4%), followed by branches and leaves. Root distribution pattern showed that most of the coarse roots were distributed in the top 40 cm of soil, whereas fine roots were concentrated in the top 20 cm. Coarse root biomass decreased with an increase in spacing. The spread of roots was asymmetrical in trees planted at 2 × 2 m and 2 × 3 m spacings, while it was symmetrical in trees planted at wide spacings. No significant difference was observed in the fine root biomass in different stands. The root:shoot ratio increased with an increase in spacing. Crop (soybean) growth and productivity varied significantly and it increased with a decrease in tree density. Soybean yield varied between 1.5 Mg ha^–1 to 2.1 Mg ha^–1. The role of root architecture of G. arborea trees on productivity of crops under agri-silviculture system is discussed.     

Growth and biomass production in Azadirachta indica seedlings in response to nutrients (N and P) and moisture stress

Production of quality seedlings is an important aspect of successful tree planting. No information is available on the effect of nutrients and water on the growth and development of the seedlings of neem (Azadirachta indica A. Juss), an important component of many tropical agroforestry systems. In an experiment in central India, the growth and nutrient-use efficiency of neem seedlings grown at various levels of light, nutrients (N and P), and water stress were determined. Seedlings were given light (diffused and complete) and nutrient (N and P) treatments comprising either high N-high P, high N-low P, low N-high P, or low N-low P. Seedlings grown in complete light (800 mol/m²/s) had four times more biomass than those grown in diffused light (200 mol/m²/s). Significant increase in seedling biomass was observed with nitrogen application, while phosphorus had no effect on biomass. Leaves contributed maximum biomass, followed by roots and stem. Nutrient use efficiency decreased with an increase in the supply of nutrients. In another experiment, containerized and bare-root seedlings were subjected to five watering treatments, viz., watering twice a week, watering weekly, watering every alternate week, watering every third week, and natural precipitation. Plant moisture stress affected both growth and survival of neem seedlings. Only 50 per cent of seedlings survived in severe drought treatment (no. 4) whereas 90 to 95 per cent seedlings showed growth in all other treatments. Plant moisture stress in severe drought treatment averaged –21 bar while in other treatments it ranged from –9 to –12 bar. Shoot-root ratio was high in bare-root seedlings as compared to containerized seedlings. Containerized seedlings had shown better endurance against drought than the bare-root seedlings. The results suggest that neem seedlings adjust their nutrient use efficiency and can be grown even under limited available resources. It is also inferred that the species can tolerate soil resource depletion caused by competitor species.This revised version was published online in November 2005 with corrections to the Cover Date.     

猪霉菌毒素中毒的新概念

霉菌毒素是真菌的次级代谢产物,可以降低畜禽生产性能和改变新陈代谢(Wannemacher等,1991)。动物采食被霉菌毒素污染的饲料而引发的病     

亚太地区霉菌毒素:普遍性、负面影响、经济后果及控制策略

抗营养因子影响饲料中营养成分的质量 ,最终降低畜禽的健康状况和生产性能。霉菌毒素就是一种存在于饲料原料和配合饲料中的抗营养因子 ,它们是由不同类属的真菌所产生的二级有毒的代谢产物。在家禽业中 ,产生霉菌毒素的真菌包括 :曲霉菌、镰刀菌、青霉菌。尽管如此多的霉菌毒素参与或导致了动物的代谢失调 ,而在亚太地区最为严重的包括 :黄曲霉毒素、赭曲霉素、橘霉素、T - 2毒素、呕吐毒素 (DON)、串珠镰孢菌毒素和玉米赤霉烯酮 (见表 1 )。由于缺乏系统分析的手段 ,更多的霉菌毒素在动物饲料中通常也无法检测出来 ,黄曲霉的存在也就意…