Componentes de produção e morfologia de raízes de mandioca sob diferentes preparos do solo

In order to evaluate the effect of minimum tillage, conventional tillage and no-tillage on yield components and the morphology of roots of sweet cassava cv. IAC 576-70 was conducted a field experiment in randomized blocks design with split plot with six replications. The different tillages: minimum tillage, conventional tillage and no-tillage plots were considered the plots and the evaluation time, in days after planting, were considered the subplots. In this experiment were mensured the number, length, diameter, fresh and dry weight, dry matter content and morphological characteristics of cassava roots at different sampling times. From the results of these assessments it was concluded that the soil tillage influence root diameter, fresh and dry weight, in the early dormancy phase and new period of vegetative growth, the soil tillage did not influence the chronological definition of the yield component as well as the morphology of cassava roots and the yield components of sweet cassava cv. IAC 576-70 are defined in the following order, number of roots, length, diameter, dry matter content, fresh and dry weight.Com o objetivo de avaliar o efeito de cultivo mínimo, plantio convencional e plantio direto sobre os componentes de produção e a morfologia das raízes tuberosas de mandioca da cultivar de mesa IAC 576-70, conduziu-se este experimento a campo em delineamento experimental de blocos ao acaso, com parcelas subdivididas com seis repetições. Os preparos do solo, cultivo mínimo, preparo convencional e plantio direto, foram consideradas as parcelas e as épocas de avaliação, em dias após o plantio, foram consideras as subparcelas. Neste experimento foram avaliados o número, comprimento, diâmetro, massas fresca e seca, teor de massa seca e as características morfológicas das raízes de mandioca em diferentes épocas de avaliação. A partir dos resultados dessas avaliações foi possível concluir que o preparo de solo influencia no diâmetro das raízes, nas massas fresca e seca no início das fases de repouso fisiológico e retomada do novo período vegetativo; que o preparo de solo não influencia a definição cronológica dos componentes de produção nem a morfologia de raízes de mandioca; e que os componentes da produção de raízes são definidos no tempo na seguinte ordem: número de raízes, comprimento, diâmetro, teor de massa seca, massas fresca e seca.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Universidade Estadual Paulista Júlio de Mesquita Filho Faculdade de Ciências Agrárias Departamento de Produção e Melhoramento VegetalUNESP FCA Instituto de BiociênciasUNESP FCA Departamento de HorticulturaInstituto Agronômico Centro de HorticulturaUniversidade Estadual Paulista Júlio de Mesquita Filho Faculdade de Ciências Agrárias Departamento de Produção e Melhoramento VegetalUNESP FCA Instituto de BiociênciasUNESP FCA Departamento de Horticultur

Water use and grain yield response of rainfed soybean to tillage-mulch practices in southeastern Nigeria

Despite the agronomic, economic and food values of soybean (Glycine max L. Merrill), there is still dearth of information on the tillage need and the implications of surface mulch for the crop in the eastern part of the forest-savanna transition zone of Nigeria. This study was therefore carried out on a sandy loam Ultisol at Nsukka with a sub-humid climate, during 2006 and 2007 cropping seasons. Our objective was to devise an appropriate tillage method for the crop from evaluated effects of no-till (NT), conventional tillage (CT) and mulch on selected key agronomic indices. Each of the NT and the CT was either unmulched (U) or mulched (M) in a split-plot, giving four treatments/tillage methods (NTU, NTM, CTU and CTM) randomized in four blocks. Rainfall was more favorable in the first than in the second season. The mean seasonal soil water storage (range, 99-109 mm) within 0.5-m soil layer differed among the treatments (NTU < CTU < NTM = CTM). However, for the first and second seasons, both water use (582-616 and 667-709 mm respectively) and grain yield (0.71-0.81 and 1.22-1.91 Mg ha-1 respectively) were not different. Mulch lowered the crop water use but had no influence on grain yield. Water use efficiency was enhanced with mulch only in the second season. Although either of the two mulch treatments (NTM/CTM) would be suitable for growing soybean especially in years of unfavorably distributed rainfall, NTM is a more rational choice than CTM. Rainfall adequacy at the critical reproductive stage of the crop showed to be a more important yield factor than the tested tillage methods

Alleviation of soil constraints to crop growth in the upland alfisols and associated soil group of the West African Sudan savannah by tied ridges

The climate of the West African Sudan savannah (annual rainfall of 600–900 mm and a monomodal rainy season of 3–4 months) is characterized by frequent long- and short-term droughts. Crop growth in the Alfisols and associated soil groups is further constrained by soil compaction, low soil fertility, high soil temperatures, low soil water retention and available water holding capacity, and low water infiltration rate. Tied ridges, ridges with earthen bunds constructed at right angles to the self-same ridges at intervals of 1–4 m, can alleviate or circumvent the above constraints, and can conserve rainfall received on-site. Water runoff with tied ridging ranges from 0 to 15% of seasonal rainfall, whereas with either open ridging or flat planting 20–45% of seasonal rainfall is lost as runoff. Soil water content is, therefore, greater with tied ridging. Tied ridging also reduces surface bulk density, maintains soil fertility by reducing losses of soil nutrients in surface runoff and improves soil water retention and available water holding capacity. The water infiltration rate in furrows of tied ridged plots is lower than that with flat planting or open ridging. With tied ridging, however, rainwater is retained on site by the ‘ties’, whereas with open ridging or flat planting it is lost as runoff. Tied ridging increases depth of rooting and subsoil root density in maize (Zea mays), millet (Pennisetum americanum) and cotton (Gossypium hirsutum) in both wet and dry years, and in cowpea (Vigna unguiculata) in dry years. Root growth of bambara groundnut (Vigna subterranea) is unaffected by tied ridging. Cowpea subsoil root growth is not significantly affected by tied ridging in wet years although root proliferation occurs in the topsoil because of the high sensitivity of cowpea to transient waterlogging. Vegetative growth and dry matter production of maize, millet, cotton, bambara groundnut, cowpea, groundnut (Arachis hypogaea) and sorghum (Sorghum bicolor) are increased by tied ridging in both wet and dry years. Grain yields of maize, millet and sorghum are increased by tied ridging, as is lint production of cotton. Cowpea grain yield is increased only in dry years. Grain yields of bambara groundnut are not significantly affected by tied ridging. Yield responses of groundnut to tied ridges are variable. Growth and yield inhibition may occur in waterlogging-sensitive crops such as cowpea and cotton during wet years. In general, greatest yield and growth increases from tied ridging occur in drought-sensitive cereal crop species and cultivars. Furthermore, strong and positive responses to tied ridges may be obtained consistently over a long period of time only in upland environments where long- and short-term droughts are frequent, soil compaction and temperatures are high, and available water-holding capacity and water infiltration rates are low

Amelioration of a highly degraded tropical alfisol by planting 1. Changes in soil physical and chemical properties

This paper examines soil amelioration by planting 15 leguminous and graminaceous plant species, including herbaceous annuals, perennials and biennials, and woody perennials and biennials. Disturbed and undisturbed natural regrowth were planted with leguminous species, in some cases with fertilizer applied at planting (400 kg ha- of 15: 15: 15 NPK). The studies were made on two highly degraded sites in southwestern Nigeria which had been subjected to intensive mechanized cropping for a period of 10 years. Changes in soil physical and chemical properties were monitored from 1989 to 1991. Acacia dificilis, Brachiaria lata and Mucuna utilis had the lowest survival rates by the following growing season. Soil fertility and compaction levels differed between sites. Planting had no effect on the latter. The decreases in compaction (i.e. macroporosity) between 0.00 and 0.10 m depth at both sites one month before and five and 17 months after planting were 43, 59 and 61 per cent, respectively were attributed to exclusion of heavy machinery from the sites. Large decreases in fertility occurred at both sites and were attributed to a combination of nutrient extraction and to leaching. Between fallow species, exchangeable Ca, pH and the cation-exchange capacity (CEC) were greater and total acids lower for herbaceous cover compared with woody perennials, and was attributed to a higher Ca demand by the latter. Highest and lowest values of Ca, CEC and pH occurred in plots where plant material was returned to the soil (i.e. by cutting or die-back) and in cropped plots, respectively. Natural regrowth was as effective or better than planted species in improving soil physical and chemical properties. Therefore the use of exotic plant species for ameliorating highly degraded alfisols is unnecessary. Amelioration of highly degraded alfisols may be best effected by allowing natural regrowth t.0 occur while excluding all mechanized traffic from the site

Contributory factors to soil spatial variability in an ultisol 1. Burning vegetation residues in heaps during land clearing

The effect of burning vegetation residues in heaps following in situprimary burning (not in heaps) during land clearing on soil properties was studied in a Typic Kandiudult in Southem Cameroon. Burning in heaps resulted in very poor or absence of plant growth during the following season. In relation to sites where burning was limited to primary burning, bulk density, penetrometer resistance, mean weight diameter of soil aggregates, pH, Bray‐l‐P, exchangeable Ca, K, and Na, and effective CEC, and soil temperatures on warm, sunny days were greater, and organic C, total N and total acidity were lower in the topsoil of sites where burning took place in heaps. The more compacted nature of the soil in such sites predisposes them to localized accelerated runoff and erosion. In general, subsoil physical and chemical properties were unaffected by burning in heaps, except for exchaneable K and Na which were greater. The absence of or poor plant growth in sites where burning occurred in heaps was attributed primarily to an imbalance in soil micronutrient availability induced by the rapid increase in pH