Maria da Conceição Santana Carvalho

Comparison of Conventional and Polymer Coated Urea as Nitrogen Sources for Lowland Rice Production

Nitrogen (N) is one of the most yield limiting nutrients in lowland rice production. Improving N use efficiency is essential to reduce cost of crop production and environmental pollution. A greenhouse experiment was conducted with the objective to compare conventional and polymer coated urea for lowland rice production. Grain yield, straw yield, panicle density, maximum root length, and root dry weight were significantly increased in a quadratic fashion with the increase of N rate from 0 to 400 mg kg−1 soil. Nitrogen source X N rate interactions for most of these traits were not significant, indicating that lowland rice responded similarly to change in N rates of two N sources. Based on regression equations, maximum grain yield was obtained with the application of 258 mg N kg−1 soil and maximum straw yield was obtained with the addition of 309 mg N kg−1 soil. Nitrogen use efficiency (grain yield per unit of N applied) was maximum for polymer coated urea compared to conventional urea. Root length and root dry weight improved at an adequate N rate, indicating importance of N fertilization in the absorption of water and nutrients and consequently yield. Polymer coated urea had higher soil exchangeable calcium (Ca) and magnesium (Mg), Ca saturation, Mg saturation, base saturation, and effective cation exchange capacity compared to conventional urea. There was a highly significant decrease in soil exchangeable potassium (K) with increasing N rates at harvest of rice plants.

Root growth of upland rice genotypes as influenced by nitrogen fertilization

The plant root system is an important organ which supplies water and nutrients to growing plants. Information is limited on influence of nitrogen fertilization on upland rice root growth. A greenhouse experiment was conducted to evaluate influence of nitrogen (N) fertilization on growth of root system of 20 upland rice genotypes. The N rate used was 0 mg kg−1(low) and 300 mg kg−1(high) of soil. Nitrogen X genotype interactions for root length and root dry weight were highly significant (P < 0.01), indicating that differences among genotypes were not consistent at two N rates. Overall, greater root length, root dry weight and tops-roots ration were obtained at an N fertilization rate of 300 mg kg−1compared with the 0 mg N kg−1soil. However, genotypes differ significantly in root length, root dry weight and top-root ratio. Nitrogen fertilization produced fine roots and more root hairs compared with absence of N fertilizer treatment. Based on root dry weight efficiency index (RDWEI) for N use efficiency, 70% genotypes were classified as efficient, 15% were classified as moderately efficient and 15% were classified as inefficient. Root dry weight efficiency index trait can be incorporated in upland rice for improving water and nutrient efficiency in favor of higher yields.

Root growth, nutrient uptake and use efficiency by roots of tropical legume cover crops as influenced by phosphorus fertilization

ABSTRACT The root is an important organ which supplies water and nutrients to growing plants. Data related to root growth and nutrient uptake by tropical legume cover crops are limited. The objective of this study was to evaluate root growth of tropical legume cover crops and nutrient uptake and use efficiency under different phosphorus (P) levels. The P levels used were 0 (low), 100 (medium) and 200 (high) mg kg−1 of soil and 5 cover crops were evaluated. Root dry weight, maximum root length, specific root length were significantly influenced by P and cover crop treatments. Maximum values of these root growth parameters were achieved with the addition of 100 mg P kg−1 soil. The P X cover crops interaction for all the macro and micronutrients, except manganese (Mn) was significant, indicating variation in uptake pattern of these nutrients by cover crops with the variation in P rates. Overall, uptake pattern of macronutrients was in the order of nitrogen>calcium>potassium>magnesium>phosphorus (N > Ca > K > Mg > P) and micronutrient uptake pattern was in the order of iron>manganese>zinc>copper (Fe > Mn > Zn > Cu). Cover crops which produced maximum root dry weight also accumulated higher amount of nutrients, including N compared to cover crops which produced lower root dry weight. Higher uptake of N compared to other nutrients by cover crops indicated that use of cover crops in the cropping systems can reduce loss of nitrate (NO3−) from soil-plant systems. Increase in root length and root dry weight with the addition of P can improve nutrient uptake from the soil and less loss of macro and micronutrients from the soil-plant systems.

Response of Upland Rice Genotypes to Nitrogen Fertilization

Nitrogen (N) is one of the most yield-limiting nutrients for upland rice production in Brazilian Oxisol soils. A field experiment was conducted for two consecutive years at the National Rice and Bean Research Centers Experimental Station Capivara with the objective to evaluate 10 promising genotypes of upland rice for N-use efficiency. The N rates used were 0 kg ha−1 (low) and 100 kg ha−1 (high). Plant height, shoot dry weight, grain yield, panicle number, and 1000-grain weight were significantly influenced by N and genotype treatments. Nitrogen × genotype interactions were not significant for most of the growth, yield, and yield components, indicating that differences among genotypes were consistent across N rates. Based on grain yield efficiency index (GYEI), genotypes were classified as N efficient or inefficient. Among 10 genotypes, four genotypes were efficient and six were moderately efficient in N use in the first year. In the second year, three genotypes were efficient and seven were moderately efficient in N use. Genotype BRA 052015 was classified as efficient in N use in both the years. Grain harvest index and GYEI had significant linear relationships with grain yield.

Fontes, doses e formas de aplicação de fósforo para o algodoeiro no Cerrado da Bahia

Ainda sao insuficientes, nas condicoes do Cerrado baiano, as informacoes sobre fontes, doses e formas de aplicacao de P para o algodoeiro, importantes para o aumento da produtividade e qualidade da fibra. Em vista disso, o objetivo deste trabalho foi definir fontes, doses e formas de aplicacao de P para a cultura do algodoeiro em solo de textura media do Cerrado da Bahia. Para tanto, foi conduzido um experimento, em plantio convencional, utilizando-se o fatorial 2 x 4 x 2 + 7 (fontes P x doses x formas de aplicacao + sete tratamentos adicionais (combinacoes de proporcoes das fontes e mais o tratamento controle (sem P)), com quatro repeticoes. As fontes avaliadas foram superfosfato triplo (ST), fosfato de Arad (FA) nas doses de 60, 120, 180 e 240 kg ha-1 de P2O5 aplicadas a lanco ou no sulco de semeadura. Os tratamentos adicionais foram constituidos de proporcoes de ST e FA para a dose de 100 kg ha-1 de P2O5. Foram avaliadas caracteristicas de producao (altura de plantas, estande, produtividade, percentagem de fibra, peso medio do capulho), teor de P foliar e P disponivel no solo e caracteristicas de qualidade da fibra. Nao houve efeito significativo de fontes, doses e formas de aplicacao sobre a produtividade do algodao em caroco. Quanto s caracteristicas de qualidade da fibra, o uso de fosfato de Arad melhorou a percentagem de fibra e o micronaire, enquanto o superfosfato triplo aumentou o comprimento da fibra. A combinacao das duas fontes resultou em maior peso medio do capulho para as proporcoes 25+75 e 75+25 (ST+FA) em relacao 50+50 (ST+FA).

Produtividade do feijoeiro irrigado em razão de fontes de adubo nitrogenado estabilizado e de liberação controlada.

Novos adubos nitrogenados estao sendo disponibilizados no mercado, mas ainda sao escassos os resultados sobre sua eficiencia nas condicoes de Cerrado. O objetivo deste trabalho foi avaliar o efeito de diferentes fontes de nitrogenio (N), inclusive a ureia com inibidor de urease e de liberacao lenta, na produtividade de graos do feijao-comum (Phaseolus vulgaris L), irrigado, em sistema plantio direto. O experimento foi conduzido no inverno de 2010, na Embrapa Arroz e Feijao, no municipio de Santo Antonio de Goias, GO. O delineamento experimental foi o de blocos ao acaso, com cinco repeticoes. Os tratamentos constaram de cinco fontes de N (ureia; ureia + NBPT; ureia + polimero; sulfato de amonio e nitrato de amonio) e um tratamento testemunha (sem N); sendo aplicados 20 kg ha-1 de N, na semeadura, e 80 kg ha-1 de N, em cobertura. Foram avaliados o Indice Relativo de Clorofila (IRC) nas folhas, o teor e o acumulo de N e a massa de materia seca da parte aerea (MSPA) do feijoeiro, no florescimento, o numero de vagens por planta, o numero de graos por vagem, a massa de 100 graos e a produtividade de graos. Nao houve diferenca significativa entre as fontes nitrogenadas, quanto ao IRC, a MSPA, ao teor de N e ao N acumulado pela planta. A utilizacao da ureia recoberta com polimero e da ureia com inibidor de urease nao proporcionou aumentos do numero de graos por vagem, do numero de vagens por planta, da massa de 100 graos e da produtividade de graos, ao se comparar com os resultados proporcionados pelas fontes tradicionais de N, como ureia, sulfato de amonio e nitrato de amonio.

Decomposição e liberação de macronutrientes da palhada de milho e braquiária, sob integração lavoura-pecuária no cerrado baiano.

Knowledge of the dynamics of decomposition and nutrient release in production systems is of great importance for management of soil fertility and reducing waste of resources. In this regard, an experiment was conducted in Cerrado (Brazilian tropical savanna) soil from the western region of Bahia, Brazil, for the purpose of studying the decomposition and nutrient release from corn stover plus Brachiaria ruziziensis straw under an integrated crop-livestock system. The evaluations were performed using litterbags collected at 0, 15, 40, 110, 170, and 220 days after desiccation of the stover/straw, which occurred in October 2008. Initial total dry matter was around 6.6 Mg ha-1, with a half-life of 115 days. Nutrient release from this volume of straw (with the percentage in relation to the total amount of nutrients accumulated in the plant) up to the end of evaluations was 29.3 (62 %), 7.8 (80 %), 42.2 (94 %), 48.6 (74 %), 17.0 (81 %), and 7.7 (79 %) kg ha-1 of N, P, K, Ca, Mg, and S, respectively. These results assist management of crop fertilization and result in less waste of natural resources. As an example, transforming the amounts of the three main macronutrients (N, P, and K) released up to 110 days (a period of a certain coincidence with the flowering of the main successor crop) into amounts of fertilizer, there would be savings of R

Nutrient Uptake and Use Efficiency of Dry Bean in Tropical Lowland Soil

243.00 per hectare.

EFICIÊNCIA AGRONÔMICA DE FOSFATOS DE ROCHA EM SOLO COM ELEVADO TEOR DE CÁLCIO TROCÁVEL

Dry bean is an important source of protein for the population of South America, and yield of this legume is very low in this continent. Knowledge of nutrient uptake and use efficiency of a crop is fundamental to improve yield. A greenhouse experiment was conducted to evaluate growth, nutrient uptake, and use efficiency of dry bean (Phaseolus vulgaris L., cv. BRS Valente) during the growth cycle. Plant samples were collected at 15, 30, 45, 60, 73, and 94 days after sowing. Root dry weight, maximum root length, shoot dry weight, and number of trifoliates were significantly increased in a quadratic fashion with the advancement of plant age. Root dry weight and number of trifoliates had significant positive association with shoot dry weight. Uptake of nutrients in the grain was in the order of nitrogen (N) > potassium (K) > calcium (Ca) > magnesium (Mg) > phosphorus (P) > iron (Fe) > manganese (Mn) > zinc (Zn) > copper (Cu). Hence, it can be concluded the N requirements for bean is greatest and Cu is minimal compared to other essential nutrients for grain yield. Uptake efficiency for root, shoot, and grain production was in the order of P > Mg > Ca > K > N > Cu > Zn > Mn > Fe. The greatest P-use efficiency among macro- and micronutrients can be considered a positive aspect of mineral nutrition of bean, because recovery efficiency of P in acidic Inceptsols is less than 20%.

Agronomic Evaluation of Phosphorus Sources Applied to Upland and Lowland Rice

No Brasil, a maioria dos trabalhos sobre a aplicacao de fosfatos de rocha foi realizada em solos do Cerrado com pH menor que 5,5 e baixos teores de Ca trocavel. Estudos em condicoes diferentes dessa, alem de raros, tem sido desestimulados, pois esses solos podem apresentar-se restritivos a dissolucao dessas fontes, a depender da especie cultivada e da natureza geologica do fosfato aplicado. Um experimento para estudar a eficiencia agronomica dos fosfatos de Bayovar e Itafos, aplicados por meio da adubacao corretiva, foi implantado em um Cambissolo Haplico Ta eutrofico vertissolico de elevado teor de Ca trocavel e pH 6. O delineamento experimental utilizado foi em blocos ao acaso com parcelas subdivididas em faixas e quatro repeticoes. As parcelas consistiam de tres tratamentos de fosfatagem, na dose de 200 kg ha-1 de P2O5, com o Fosfato Natural Reativo de Bayovar, o Fosfato de Rocha Itafos e o superfosfato triplo (fonte de referencia), alem de um tratamento-padrao sem correcao de P. As subparcelas correspondiam aos tres niveis de adubacao de manutencao (0, 60 e 120 kg ha-1 de P2O5) aplicados anualmente no sulco de semeadura, utilizando superfosfato triplo. Cultivou-se milho nos dois anos em que o experimento foi conduzido (2011 e 2012). No periodo avaliado, a produtividade de graos e o teor de P foliar do milho indicaram menores necessidades de reposicao de P, por meio das doses de manutencao, conforme maior era a solubilidade da fonte corretiva aplicada. Tanto Mehlich-1 quanto a Resina de Troca Ionica Mista removeram mais P dos tratamentos em que foram aplicados fosfatos de rocha em relacao ao tratamento onde foi aplicado o superfosfato triplo via adubacao corretiva. Quando aplicados de maneira isolada (dose 0 de manutencao), os indices de eficiencia agronomica dos fosfatos de rocha foram de 72,08 e 82,31% para o Bayovar e de 43,85 e 47,47% para o Itafos nos anos de 2011 e 2012, respectivamente. No periodo avaliado, os tratamentos de maior economicidade foram a fosfatagem com o superfosfato triplo nas doses de manutencao de 0 e 60 kg ha-1 de P2O5 e a com o fosfato reativo de Bayovar, nas doses de 60 e 120 kg ha-1 de P2O5.