Effect of plant age on in-soil decomposition and nitrogen content of sunn hemp tissue

ABSTRACT

The effects of plant age at the time of mowing on sunn hemp (Crotalaria juncea L.) tissue decomposition, nitrogen (N) release, and fiber content in Krome very gravelly loam were assessed. Combined leaf and stem tissue from 42-, 77- or 112-day-old sunn hemp plants was placed in mesh bags and buried below the soil surface in the field. Bags were removed bi-weekly and dry weights, N concentration, acid detergent fiber (ADF) and neutral detergent fiber (NDF) concentrations in buried sunn hemp tissues were determined. There was a rapid decrease plant tissue dry weight during the first 14 days after tissue was buried, followed by a slow gradual decrease. The amount N per hectare was much lower for 42-day-old than 112-day-old sunn hemp. Tissue of the youngest plants decomposed the quickest. Forty two-day-old tissue had a higher N concentration, N mineralization rate, and lower NDF and ADF than 77- or 112-day-old tissue. Mowing and soil incorporation of a 42-day-old instead of a 77- to 112-day-old sunn hemp cover crop prior to planting a cash crop can be beneficial for a fast-growing cash crop planted soon after soil incorporation of the cover crop.     

猪屎豆种子多糖提取工艺优化

利用单因素试验和和L9(33)正交试验优化了热水浸提法提取猪屎豆种子多糖的提取工艺.结果表明,影响猪屎豆种子多糖提取的因素依次为提取时间、提取温度和料液比,最优工艺条件为料液比1∶30、浸提温度40℃、浸提时间2.5 h、醇沉浓度95％,猪屎豆种子多糖提取率为15.43％.紫外检测和茚三酮法检测未见多糖含有核酸、蛋白质.     

Green manures for maize—bean systems in eastern Uganda: Agronomic performance and farmers' perceptions

Researchers worked with farmers in eastern Uganda to develop alternatives for soil management using crotalaria (Crotalaria ochroleuca), mucuna (Mucuna pruriens var. utilis), lablab (Dolichos lablab), and canavalia (Canavalia ensiformis) as green manures in short-term fallows. The participatory research was part of a community-based approach for systems improvement. Grain yields of maize (Zea mays) and bean (Phaseolus vulgaris) following one season of crotalaria fallow were 41% and 43%, respectively, more than following a two-season weedy fallow. Grain yields of maize following a one-season fallow with mucuna and lablab were 60% and 50% higher, respectively, as compared with maize following maize. Maize and bean yield were more, although effects were small, during the second and third subsequent seasons, indicating probable residual effects of the green manures. Mucuna and lablab were successfully produced by intersowing into maize at three weeks after sowing maize, although the yields of the associated maize crop were reduced by 24% to 28%. Farmers estimated the labor requirements for mucuna and lablab to be less than for crotalaria. Farmers independently experimented on how these species can be integrated into banana (Musa spp.), coffee (Coffea robusta), sweet potato (Ipomoea batatas), and cassava (Manihot esculenta) production systems. Farmers reported that the beneficial effects of the green manures included higher food-crop yields; weed suppression; improved soil fertility, soil moisture, and soil tilth; and erosion control. Mucuna and lablab were preferred because of reduced labor requirements and increased net benefits compared with continuous cropping. Farmer participation in the green manure research resulted in efficient generation and adaptation of green manure technology now being promoted in eastern and central Uganda.This revised version was published online in November 2005 with corrections to the Cover Date.     

猪屎豆不同部位黄酮含量的测定及比较

[目的]研究猪屎豆不同部位不同提取相的黄酮含量。[方法]采用乙醇回流提取作为猪屎豆黄酮的制备方法;以芦丁为对照品,采用紫外-可见分光光度法作为黄酮的测定方法。[结果]叶片石油醚相、氯仿相、乙酸乙酯相和水相的黄酮含量分别为14.63、92.67、8.29、98.80 mg/g,果实各萃取相黄酮含量分别为3.24、30.54、52.15、59.72 mg/g;猪屎豆叶片石油醚相、氯仿相和水相的黄酮含量显著高于果实相应的黄酮含量,果实乙酸乙酯相的黄酮含量显著高于叶片乙酸乙酯相的黄酮含量。[结论]猪屎豆叶片和果实可作为黄酮开发利用的重要来源之一。     

Effects of pyrrolizidine alkaloids on the performance of plant‐parasitic and free‐living nematodes

BACKGROUND: Chemical nematicides such as methyl bromide have for decades played a significant role in the management of plant‐parasitic nematodes. Their application is problematic because of negative environmental impacts, and therefore methyl bromide was phased out in Europe in 2005. A possible alternative to synthetically derived nematicides is seen in the use of plants and/or their secondary metabolites. These plants could either be used as nematicidal green manure or as a source for nematicidal extracts. This study aimed to evaluate the effects of 1,2‐dehydropyrrolizidine alkaloids (PAs), a group of secondary plant metabolites found in hundreds of plant species throughout the world, on the performance of plant‐parasitic and free‐living nematodes. RESULTS: PAs induced nematicidal, ovicidal and repellent effects on different plant‐parasitic and free‐living nematodes. There was no conclusive ranking in toxicity for the different structural types of PAs tested. However, the effects were often more pronounced for the tertiary than for the oxidised form of PAs. Further, large differences were observed in the susceptibility of different nematode species to PAs. CONCLUSIONS: PAs do affect several performance parameters and developmental stages of nematodes. Therefore, PA‐producing plants such as species of Crotalaria, Ageratum or Senecio might be promising candidates for nematode management strategies. [Correction made here after initial online publication] Copyright © 2009 Society of Chemical Industry     

Effects of dietary Crotalaria pallida seeds on the health and performance of laying hens and evaluation of residues in eggs

The effect of three dietary concentrations of Crotalaria pallida (C. pallida) seeds (0, 1, 2, and 3% w/w) of their normal diet were investigated in commercial laying hens during a 35 day feeding trial. All concentrations of C. pallida decreased body weight and feed intake (P < 0.05). Egg mass production and average egg weight were decreased by feeding of ≥2% C. pallida seeds (P < 0.05). All concentrations of C. pallida increased relative lung weight and serum activity of ALT, AST and LDH (P < 0.05); 3% C. pallida seeds decreased liver weight (P < 0.05). Analysis of the C. pallida seeds for dehydropyrrolizidine alkaloid content detected usaramine and its N-oxide at a total alkaloid concentration of 0.18% (dry weight). Usaramine was also detected in the eggs of all hens fed C. pallida seeds.