Alberto Baêta dos Santos

Yield Physiology of Dry Bean

ABSTRACT Dry bean (Phaseolus vulgaris L.) is an important food legume for the world population. However, its average yield is low worldwide. The main reasons for low yield are biotic and abiotic stresses. Maximum economic yield of a crop can be achieved with appropriate balance between plant and environmental factors during crop growth cycle. Adopting appropriate management practices in favor of high yields can modify some of these factors. Hence, knowledge of yield physiology of dry bean is important for understanding yield formation components during crop growth and development and consequently improving yield. Dry bean growth cycle is divided into vegetative and reproductive growth stages. During vegetative stage, development of roots, trifoliate, node, and branches take place. Main features of reproductive growth stage are flowering, pod and grain formation. Important plant traits associated with yield are root and shoot dry matter yield, pod number, 100 grain weight, leaf area index, grain harvest index, and nitrogen harvest index. These plant traits are genetically controlled and also influenced by soil and plant management practices. Higher yield is possible only when there is an adequate balance among various physiological processes or yield components. The objective of this review is to discuss growth and development of bean plant including yield formation process or traits during crop growth cycle and importance of these yield components in determining yield.

Iron Toxicity in Lowland Rice

ABSTRACT Lowland rice is a staple food for more than 50% world population. Iron toxicity is one of the main nutritional disorders, which limits yield of lowland rice in various parts of the world. The toxicity of iron is associated with reduced soil condition of submerged or flooded soils, which increases concentration and uptake of iron (Fe2 +). Higher concentration of Fe2 + in the rhizosphere also has antagonistic effects on the uptake of many essential nutrients and consequently yields reduction. In addition to reduced condition, increase in concentration of Fe2 + in submerged soils of lowland rice is associated with iron content of parent material, oxidation-reduction potential, soil pH, ionic concentration, fertility level, and lowland rice genotypes. Oxidation-reduction potential of highly reduced soil is in the range of –100 to –300 mV. Iron toxicity has been observed in flooded soils with a pH below 5.8 when aerobic and pH below 6.5 when anaerobic. Visual toxicity symptoms on plants, soil and plant tissue test are major diagnostic techniques for identifying iron toxicity. Appropriate management practices like liming acid soils, improving soil fertility, soil drainage at certain growth stage of crop, use of manganese as antagonistic element in the uptake of Fe2 + and planting Fe2 + resistant rice cultivars can reduce problem of iron toxicity.

Chemistry of Lowland Rice Soils and Nutrient Availability

Rice is the staple food crop for about 50% of the worlds population. It is grown mainly under two ecosystems, known as upland and lowland. Lowland rice contributes about 76% of the global rice production. The anaerobic soil environment created by flood irrigation of lowland rice brings several chemical changes in the rice rhizosphere that may influence growth and development and consequently yield. The main changes that occur in flooded or waterlogged rice soils are decreases in oxidation–reduction or redox potential and increases in iron (Fe2+) and manganese (Mn2+) concentrations because of the reductions of Fe3+ to Fe2+ and Mn4+ to Mn2+. The pH of acidic soils increased and alkaline soils decreased because of flooding. Other results are the reduction of nitrate (NO3 −) and nitrogen dioxide (NO2 −) to dinitrogen (N2) and nitrous oxide (N2O); reduction of sulfate (SO4 2−) to sulfide (S2−); reduction of carbon dioxide (CO2) to methane (CH4); improvement in the concentration and availability of phosphorus (P), calcium (Ca), magnesium (Mg), Fe, Mn, molybdenum (Mo), and silicon (Si); and decrease in concentration and availability of zinc (Zn), copper (Cu), and sulfur (S). Uptake of nitrogen (N) may increase if properly managed or applied in the reduced soil layer. The chemical changes occur because of physical reactions between the soil and water and also because of biological activities of anaerobic microorganisms. The magnitude of these chemical changes is determined by soil type, soil organic-matter content, soil fertility, cultivars, and microbial activities. The exclusion of oxygen (O2) from the flooded soils is accompanied by an increase of other gases (CO2, CH4, and H2), produced largely through processes of microbial respiration. The knowledge of the chemistry of lowland rice soils is important for fertility management and maximizing rice yield. This review discusses physical, biological, and chemical changes in flooded or lowland rice soils.

Manejo do nitrogênio para eficiência de uso por cultivares de feijoeiro em várzea tropical

O objetivo deste trabalho foi avaliar a resposta e a eficiencia do uso de N, por cultivares de feijoeiro, em funcao do manejo do fertilizante nitrogenado em solo de varzea. O delineamento experimental foi o inteiramente casualizado, com seis repeticoes, no esquema de parcelas divididas constituidas pelos manejos de N, e as subparcelas pelas cultivares. A aplicacao de N no sulco de semeadura causou efeito salino do fertilizante, o que reduziu a populacao de feijoeiros. A incorporacao de todo o N em sulcos distintos das linhas da semeadura, por ocasiao dessa ou ate 15 dias apos a emergencia, e mais eficaz no aumento da produtividade de graos de feijao, do que a aplicacao a lanco na superficie ou incorporada com grade antes da semeadura. A cultivar BRS Pontal foi a mais produtiva, o que e indicativo de alta adaptacao ao ambiente de varzea tropical. Houve diversidade na eficiencia de uso de N entre as cultivares de feijoeiro, e as de ciclo medio foram mais eficientes do que as precoces. A produtividade de graos foi positivamente associada as eficiencias agronomica, de recuperacao e de utilizacao de N. A produtividade de graos e a eficiencia de uso de N pelas cultivares diferem conforme o manejo do fertilizante nitrogenado.

Rice Ratooning Management Practices for Higher Yields

Rice is one of the worlds most important cereal crops and rice ratooning is one of the potential technologies to increase rice production. Based on land and water management, rice ecosystem is mainly divided into lowland, upland and deep water or floating rice. Rice ratooning is mainly practiced on lowland rice ecosystem. Ratooning provides higher resource use efficiency per unit time and per unit land area. However, better yield of ratoon crop is possible by adopting appropriate management practices for main crop as well as for ratoon crop. These management practices include land preparation, adequate plant density and spacing, use of appropriate cultivars, water management, application of adequate rate of fertilizers, appropriate height of cutting, and control of diseases, insects and weeds.

Eficiência de uso de nitrogênio em cobertura pelo feijoeiro irrigado

Entre as tecnicas de manejo necessarias para atingir alto potencial produtivo nos sistemas agricolas irrigados, esta a adubacao nitrogenada. O objetivo deste trabalho foi avaliar os efeitos de doses de nitrogenio aplicadas em cobertura sobre a fitomassa e a eficiencia de uso do nutriente pela cultivar BRS Horizonte de feijoeiro. O experimento foi conduzido na Embrapa Arroz e Feijao, em um Latossolo Vermelho distrofico, em delineamento experimental de blocos ao acaso, com quatro repeticoes e cinco doses de nitrogenio, 0, 30, 60, 120 e 240 kg ha-1, na forma de ureia, aplicadas em cobertura metade aos dez dias apos a emergencia (DAE) e a outra metade aos 17 DAE. A fitomassa no florescimento do feijoeiro relacionou-se linearmente com as doses de N aplicadas em cobertura, ao passo que a fitomassa na colheita apresentou resposta quadratica. As relacoes entre o indice de colheita de graos e o indice de colheita de N com as doses de N foram quadraticas e os indices maximos foram estimados com a dose de 140 kg ha-1 de N. A eficiencia de uso de nitrogenio pelo feijoeiro variou com as doses de N aplicadas e com o tipo de eficiencia calculada, enquanto as eficiencias agronomica e fisiologica diminuiram com o incremento da dose.

LOWLAND RICE GENOTYPES EVALUATION FOR PHOSPHORUS USE EFFICIENCY IN TROPICAL LOWLAND

Lowland rice is a staple food for more than 50% of the worlds population and phosphorus (P) deficiency is one of the main constraints in rice production in tropical lowlands. A field experiment was conducted for two years consecutive with the objective to evaluate 12 lowland rice genotypes for P use efficiency. The P rates used were 0, 22, 44, 66, and 88 kg P ha−1 (0, 50, 100, 150 and 200 kg P2O5 ha−1) applied to an Inceptisol. The genotypes used were BRS Jaçanã, CNAi 8860, BRS Fronteira, CNAi 8879, CNAi 8880, CNAi 8886, CNAi 8885, CNAi 8569, BRSGO Guará, BRS Alvorada, BRS Jaburu and BRS Biguá. There were significant and quadratic responses of genotypes to phosphorus fertilization. Adequate P rates for maximum grain yield varied from genotype to genotype. However, across 12 genotypes, maximum grain yield was obtained with the application of 54 kg P ha−1. Genotype BRS Jaçanã was most efficient and genotype CNAi 8569 was most inefficient in P use efficiency. Shoot dry weight and panicle number was also increased significantly and quadratically with increasing P rates in the range of 0 to 88 kg P ha−1. These two plant parameters were positively associated with grain yield. Agronomic efficiency (kg grain produced per kg P applied) was significantly decreased with increasing P rates in the range of 22 to 88 kg P ha−1.

Dry Matter and Yield of Lowland Rice Genotypes as Influence by Nitrogen Fertilization

ABSTRACT Rice is a staple food for more than 50% of the worlds population and nitrogen (N) is one of the most yield limiting nutrients in lowland rice ecosystems. A field experiment was conducted for two consecutive years to evaluate dry matter production and grain yield of 12 lowland rice genotypes (BRS Jaçanã, CNAi 8860, BRS Fronteira, CNAi 8879, CNAi 8880, CNAi 8886, CNAi 8885, CNAi 8569, BRSGO Guará, BRS Alvorada, BRS Jaburu, and BRS Biguá) at five N rates (0, 50, 100, 150, and 200 kg ha− 1). Genotypes showed significant variation in grain yield and shoot dry weight. Genotype BRSGO Guará was highest yielding, whereas genotype BRS Jaburu was lowest yielding and the remaining genotypes were intermediate in grain yielding potential. Grain yield and shoot dry weight were having significant quadratic increase with increasing N rates in the range of 0 to 200 kg ha− 1. However, 90% of the maximum yield is often considered as an economical rate, which was 120 kg for shoot dry weight and 136 kg N ha− 1 for grain yield. Shoot dry matter was having significant positive quadratic association with grain yield across 12 genotypes.

Adubação nitrogenada na produtividade, leitura SPAD e teor de nitrogênio em folhas de feijoeiro

Nitrogen deficiency is one of the most limiting yield factors for dry bean. The objective of this study was to evaluate effects of topdressing nitrogen on chlorophyll and nitrogen concentrations in dry bean (BRS Horizonte cultivar) leaves and yield. The experiment was conducted at Embrapa Arroz e Feijao, in Santo Antonio de Goias, Goias State, Brazil, using a dystrophic dark red latosol. The experimental design was randomized blocks with four replications. The nitrogen rates used were 0 kg ha -1 , 30 kg ha -1 , 60 kg ha -1 , 120 kg ha -1 , and 240 kg ha -1 . Half of the N was applied at 10 days after emergence and half was applied at 17 days after emergence, using urea as fertilizer. Grain yield and chlorophyll concentration showed quadratic response to increasing N rates, whereas N concentration in leaves increased linearly. The chlorophyll concentration increased according to plant age, while the N concentration in leaves decreased. Chlorophyll and N concentrations in leaves were positively associated with grain yield. Chlorophyll meter readings estimated adequately chlorophyll concentrations in dry bean leaves and can be used to diagnose this nutrient in dry bean. KEY-WORDS: Phaseolus vulgaris ; chlorophyll meter; nitrogen level; no-till system.

Manejo de água e de fertilizante potássico na cultura de arroz irrigado

Irrigation water levels and timing of potassium fertilization is extremely important for the use of lowlands for irrigated rice (Oryza sativa L.) cultivation in crop rotation. A field experiment was conduced for three consecutive years in Inceptisol to study the effects of water management (WM1 - continuous flooding and WM2 - intermittent flooding followed continuous flooding) and mode of potassium fertilizer application (K1 - at sowing; K2 - fractional application and K3 - fractional application of half levels) on grain yield and yield components of irrigated rice. Water management presented expressive effect on rice performance as compared to potassium fertilization. Continuous flooding during whole growing cycle of crop had higher grain yield as well as higher values of yield components and grain quality. Fractional potassium fertilization increased its utilization efficiency. Potassium fertilizer management affected differently rice crop performance according to forms of water management.