Persistência e liberação de nutrientes da palha de milho, braquiária e labe-labe / Persistence and nutrient release from maize, brachiaria and lablab straw

A velocidade de liberação de nutrientes da palha e persistência do material vegetal depositado sobre o solo são fatores determinantes no sucesso do Sistema Semeadura Direta. Objetivou-se avaliar a persistência e a liberação de nutrientes dos resíduos vegetais de milho, braquiária e labe-labe depositados na superfície do solo. O experimento foi instalado em 05 de maio de 2010, na UNOESTE (Presidente Prudente-SP). Utilizou-se o delineamento experimental inteiramente casualizado, com 3 repetições, em esquema fatorial 3x4, sendo três espécies vegetais (labe-labe, milho e braquiária) e 4 épocas de avaliação (0, 45, 90 e 135 dias). Os resíduos vegetais foram colocados no interior de sacos telados de 0,20 x 0,30 m, conhecendo-se a umidade de cada material, e conseqüentemente a matéria seca inicial. Em cada época de amostragem foram avaliados os teores de N, P, K e Mg da palha e porcentagem de matéria seca remanescente de cada material, além das relações C:N dos resíduos. A cobertura de labe-labe apresentou a menor persistência entre as espécies estudadas. Todas as espécies apresentaram maior redução de massa seca nos primeiros 45 dias de avaliação. O potássio foi o elemento liberado com maior facilidade das palhas. Todas as espécies estudadas apresentaram maior liberação de nutrientes nos primeiros 45 dias após deposição da cobertura sobre o solo, com exceção para Mg que foi extraído da palha de milho com maior intensidade entre 45 e 90 dias. As palhas de milho e braquiária são mais indicadas para cobertura do solo, pois além proporcionar proteção do solo por mais tempo também são eficientes na reciclagem de nutrientes.

The rate of nutrient release from straw and the plant material persistence deposited on the soil are factors that will determine the success of the no tillage system. The objective of this study was to evaluate the persistence and nutrient release from crop residues of maize, brachiaria and lablab deposited on the soil surface. The experiment was installed in May 05, 2010, in the University of Oeste Paulista (Presidente Prudente-SP). We used a completely randomized design with three replicates in a 3x4 factorial design, with three plant species (lablab, maize and brachiaria) and four times of assessment after the deposition of residues on the soil (0, 45, 90 and 135 days). The plant residues were placed into litter bags of 0.20 x 0.30 m. The initial fresh weight of the lablab, maize and brachiaria residues placed within the litter bags were 200, 150 and 150 g, respectively, knowing the moisture content of each material, and consequently the initial dry matter. At each sampling time were evaluated for N, P, K and Mg of straw and dry matter percentage of each remaining material, in addition to the C: N ratios of the straw. Statistical analysis consisted of regression study and test Tukey (p<5%). The lablab straw had the lowest persistence of the species studied, reducing its dry weight by 55% after 135 days. All species had higher dry matter reduction in the first 45 days of evaluation. The potassium was the element of easiest release of the straws, with reduction from 60 to 77% of K accumulated in plant tissue. The maize and brachiaria straw are more suitable for cover crop, as well as provide soil protection for longer time, also are efficient in recycling nutrients.

Supplemental UV-B radiation induced changes in growth, pigments and antioxidant pool of bean (Dolichos lablab) under field conditions.

Present study is conducted to evaluate the response of bean (Dolichos lablab cv . pusa early prolific) plants to supplemental UV-B (sUV-B: 280-315 nm: 7.2 kJ m-2 d-1) radiation. UV-B caused alteration in biomass translocation pattern with more retention of biomass in below ground parts leading to an increment in root shoot ratio. Specific leaf area (SLA) which is the measure of leaf thinness, increased in plants under sUV-B exposure by 95.7 and 82.3% after 15 and 30 days after germination. Photosynthetic machinery of bean plants was the potential target of UV-B as photosynthetic rate was decreased by 88.6 % at 30 days after germination. sUV-B lead to the formation of reactive oxygen species thus generating oxidative stress. Stimulation of antioxidant defense system (enzymatic and non-enzymatic) was observed due to sUV-B radiation. Phenolic content decreased (34.7 and 18.6%) but protein showed varied response, increased initially (34%) thereafter declined (10.2%) under sUV-B radiation.

The nature of lectins from Dolichos lablab.

The lectins from the seeds of Dolichos lablab var. lignosus (field bean) and Dolichos lablab var. typicus (lablab bean) have been isolated in a homogeneous form by affinity chromatography on D-mannose linked Sepharose. Both the lectins are glycoproteins and have a molecular weight of 60,000 and S 20,w value of 5·2 and seem to be made up of 4 similar subunits (apparent molecular weight 15,000). The carbohydrate content ofthe lectins is mostly fucose (2-5 mol per mol of protein), mannose (5-8 mol per mol of protein) and N-acetyl glucosamine (1–2 mol per mol of protein). The amino acid composition of both the lectins was similar and methionine and half cystine could not be detected, Both the lectins have similar tryptic peptide map. Alanine and serine were the only Ν and C-terminal amino acids for both lectins. The lectins were found to contain low amounts of bound metals such as manganese, magnesium and calcium. The near ultra-violet circular dichroism spectra of the lectins are similar to that of Sainfoin. Circular dichroism data indicate that tyrosine and tryptophan residues are involved in sugar binding. The lectins are nonspecific for human blood groups and they agglutinate a variety of other erythrocytes. Among a number of sugars, D-glucose and D-mannose inhibited the haemagglutinating activity of the lectins. The lectins were antigenically similar.

Toxic and antigrowth effects of raw and processed field bean (Dolichos lablab) on albino rats.

Samples of freeze dried green field bean (Dolichos lablab) and dry mature bean, were subjected to the following processing methods—heat processing, extraction with 80% ethanol, hexane or dilute acid, protein isolation; and these samples were evaluated for growth promoting value and toxicity. Extraction with 80% ethanol or with dilute acid increased survival period of the animals; but these did not promote growth. Heat processing was essential to destroy antinutritional factors and promote growth. Extraction of the beans with 80% ethanol did not however alter the trypsin inhibitor or haemagglutinin activities. The protein isolate and acid-extracted residue which had low trypsin inhibitor and haemagglutinin activities, did not also promote growth. Thus the trypsin inhibtor and haemagglutinin activities did not completely account for the toxicity to albino rats. However, heat processing of ethanol extracted bean flour indicated that the beneficial effect of ethanol extraction was not apparent, once the samples were heat processed. Dry mature bean dhal was more toxic than the whole bean either dry or green. Supplementation of heat processed field bean with methionine and tryptophan promoted good growth of albino rats and significantly increased the protein efficiency ratio.