Cristiane Prezotto Silveira

Morfogênese e produção de biomassa do capim-tanzânia adubado com nitrogênio e cálcio

The objective of this study was to evaluate grass responses to combined rates of nitrogen and calcium. Measured response variables included leaf number, tiller number, leaf area, and DM yield. Tanzaniagrass was grown in nutrient solution with ground quartz as substrate, in a greenhouse experiment. The experiment was carried out in randomized block design, with four replications. A fractionated 52 factorial was used, with combinations of five nitrogen rates (2, 9, 16, 23, and 30 mmol L-1) and five calcium rates (0.50, 1.75, 3.00, 4.25, and 5.50 mmol L-1). Three harvests were performed, the first one 39 days after seedlings transplanting, the second one 30 days after the first harvest, and the third one 28 days after the second harvest. Calcium rates did not interact with the nitrogen rates for the productive variables in the first growth of this grass. The number of tillers and leaves depended only on nitrogen rates. Combination of nitrogen and calcium rates was necessary for tanzaniagrass leaf area at the third growth, and for the shoot biomass at the second and third growths. Maximum productive responses of this forage were reached with the minimum supply of nitrogen of 23 mmol L-1. The use of calcium at rate not inferior to 2 mmol L-1 did not reduce productive variables of this grass, even with the supply of high nitrogen rate.

Testing and validation of methods for the diagnosis and recomendation integrated system for Signal grass

O Sistema Integrado de Diagnose e Recomendacao (DRIS) permite a interpretacao dos resultados de analise foliar, utilizando relacoes entre nutrientes, ao inves da concentracao absoluta e isolada de cada um deles, utilizada pelo criterio de faixa de suficiencia. Objetivou-se avaliar tres procedimentos de calculo dos indices DRIS, bem como verificar a eficiencia do DRIS como metodo de interpretacao de resultados de analises de folhas da Brachiaria decumbens (capim-Braquiaria). O estudo foi desenvolvido com os resultados de seis experimentos realizados em casa-de-vegetacao em Piracicaba, SP, com solucao nutritiva. Foram empregadas as concentracoes de N, P, K, Ca, Mg, S, Cu, Fe, Mn e Zn nas amostras de lâminas foliares recem-expandidas do capim. Para a validacao do metodo DRIS foram utilizados resultados de um experimento com aplicacao de doses de nitrogenio e enxofre realizado com o mesmo capim proveniente da Fazenda Mundo Novo, em Brotas, SP. Os indices DRIS foram calculados por dois criterios para escolha da ordem da razao dos nutrientes (valor F e valor R) e tres formas de calculo das funcoes dos nutrientes (metodos de Beaufils, Jones e Elwali & Gascho). O Indice de Balanco Nutricional (IBN), calculado a partir das normas geradas, apresentou coeficientes de correlacao negativos e significativos com a produtividade nas combinacoes de metodos testados e os metodos DRIS propostos por Beaufils, Jones e Elwali & Gascho foram eficientes em detectar concentracoes que revelam a deficiencia ou o excesso dos nutrientes.

Norms for the diagnosis and recommendation integrated system for Signal grass

The Diagnosis and Recommendation Integrated System (DRIS) has been proved efficient as a method for nutritional diagnosis in several crops. However there is a lack of information on the use of DRIS for tropical forage grass. The aim of this paper was to establish norms for interpretation of results of analysis from recently expanded leaf laminae of Brachiaria decumbens Stapf. (Signal grass), through the DRIS method. To establish DRIS norms, concentrations of N, P, K, Ca, Mg, S, Cu, Fe, Mn, and Zn and the relative production obtained in six experiments conducted in greenhouse using nutrient solution and silica as substrate were considered. DRIS indices were calculated using two criteria in order to choose the ratio order of nutrients: F value - ratio of variance for the relationships among nutrients between the reference group and the low productivity group; and R value - correlation coefficients between the productivity values and the relationship among the pairs of nutrients, and three forms of calculation for the functions of nutrients (methods of Beaufils, of Jones, and of Elwali & Gascho). The two criteria to choose the ratio order of nutrients selected different ratios between pairs of nutrients; the nutrient concentrations were positively and significantly correlated with the respective DRIS indices, except for N; and DRIS norms are useful for the nutritional diagnosis of the ten studied nutrients in leaf laminae of Signal grass.

Influência da adubação com nitrogênio e cálcio nas características morfológicas e produtivas das raízes de capim-tanzânia cultivado em solução nutritiva

Root traits of Panicum maximum Jacq. Cv. Tanzânia were evaluated in response to a nutritive solution with combinations of nitrogen and calcium rates. Ground quartz was used as substrate in an experiment carried out in a greenhouse in the spring, using a complete randomized block design, with four replications, in a fractionated 52 factorial scheme, with 13 combinations of nitrogen and calcium, in mmol/L: 2-0.5; 2-3.0; 2-5.5; 9-1.75; 9-4.25; 16-0.5; 16-3.0; 16-5.5; 23-1.75; 23-4.25; 30-0.5; 30-3.0, and 30-5.5. After the third harvest, grass roots were collected. Combination of high rates of nitrogen with low rates of calcium provided maximal dry matter yields and concentration of nitrogen in the roots. Critical levels of nitrogen and calcium in the roots of Tanzania grass were 11.07 and 1.30 g/kg, respectively. Significant correlation coefficients were found for dry mass, total length and total surface of the roots. Length and total surface and specific length and surface of the roots depend on the supply of nitrogen, but do not depend on the calcium supply. Calcium rates are determinant for this nutrient concentration in the grass roots.

Two years of nitrogen and sulfur fertilizations in a signal grass pasture under degradation: changes in the root system

The objective of this research was to evaluate the effect of combinations of nitrogen and sulfur rates in degraded signal grass (Brachiaria decumbens) pasture on their productive, morphological and nutritional attributes in the root system at four soil depths. The pasture used in the experiment was established over eight years ago in Entisol. Five nitrogen rates (0; 150; 300; 450 and 600 kg/ha/year) and five sulfur rates (0; 15; 30; 45 and 60 kg/ha/year) were combined in a fractionated factorial in a randomized block design, with three replications. Nitrogen was supplied as ammonium nitrate and sulfur as gypsum, and the rates were split into three times in the rainy season. The evaluations occurred at intervals of 35 days during the rainy season and 56 days in the dry season, in two consecutive years. Roots were collected with a 4-cm diameter auger at 0-10; 10-20; 20-30 and 30-40 cm soil depths. It was determined root dry matter, length and surface of the root system and nitrogen and sulfur concentrations in roots. Nitrogen rates applied in two consecutive years in the pasture affected dry mass, length, surface and nitrogen concentration in signal grass root system. Rates of sulfur by themselves or combined with nitrogen rates do not affect attributes of root system.

Macronutrients concentrations in Tanzania guineagrass diagnostic leaves supplied with nitrogen and calcium rates

An experiment under greenhouse conditions was carried out with Tanzania guineagrass supplied with combined rates of nitrogen and calcium in nutrient solutions during the spring season. A randomized block design was used, with four replicates, in an incomplete 52 factorial scheme with five nitrogen rates (2; 9; 16; 23 e 30 mmol L-1) and five calcium rates (0.50; 1.75; 3.00; 4.25 e 5.50 mmol L-1) resulting in 13 nitrogen:calcium combinations (mmol L-1): 2:0.50; 2:3.00; 2:5.50; 9:1.75; 9:4.25; 16:0.50; 16:3.00; 16:5.50; 23:1.75; 23:4.25; 30:0.50; 30:3.00 and 30:5.50. Macronutrient concentrations were determined in the two recently expanded leaf blades (diagnostic leaves) collected in the three harvests of Tanzania guineagrass. The results showed that, in the first harvest of the plants, calcium rates did not interact with nitrogen for any of the nutritional traits, except for sulphur concentration in the diagnostic leaves. The interaction nitrogen × calcium was significant for concentrations of calcium and sulphur in the diagnostic leaves at the second and third samplings of the grass. Nitrogen rates and, not calcium rates, are determinant for nitrogen, phosphorus, and potassium concentrations in the diagnostic leaves of Tanzania guineagrass. The concentration of calcium at the first harvest of the grass depends only on the supply of this nutrient. Concentration of magnesium in plant tissue decreases as nitrogen or calcium supply increases. Reduction of calcium to 40% of that one used in the nutrient solution does not reduce nutritional parameters of this grass, even with the supply of high nitrogen rate.

Valor nutritivo do capim-braquiária no primeiro ano de recuperação com aplicações de nitrogênio e enxofre

Objetivou-se estudar a influencia das combinacoes de doses de nitrogenio e de enxofre na recuperacao de pastagens de capim-braquiaria (Brachiaria decumbens) por meio da avaliacao do valor nutritivo do capim nos periodos chuvoso e seco de um ano agricola. O experimento foi realizado em pastagem degradada de capim-braquiaria, num delineamento de blocos ao acaso, em fatorial 5 × 5, com cinco doses de nitrogenio (0, 150, 300, 450 e 600 kg/ha/ano) e cinco de enxofre (0, 15, 30, 45 e 60 kg/ha/ano), com tres repeticoes por combinacao. As avaliacoes no campo foram realizadas a cada 35 dias no periodo das aguas (de 21/12/2005 a 10/5/2006), totalizando cinco avaliacoes, e a cada 56 dias no periodo da seca (de 5/7/2006 a 25/10/2006), totalizando tres avaliacoes. Os cortes das plantas a 10 cm da superficie do solo foram realizados em area delimitada de 0,25 m2. A combinacao das doses de nitrogenio e de enxofre alterou as concentracoes de proteina bruta, fibra em detergente neutro e fibra em detergente acido na primeira avaliacao do periodo seco. O nitrogenio foi o nutriente que mais influenciou no valor nutritivo do capim-braquiaria, resultando em variacoes nas concentracoes desses nutrientes e na digestibilidade in vitro da massa seca. O enxofre promove variacao significativa na DIVMS no periodo chuvoso.

Produção de biomassa, diagnose nutricional e absorção de nitrogênio e cálcio durante crescimento inicial do pinhão-manso

Higher nitrogen (N) and calcium (Ca) requirements than other macronutrients in Euphorbiaceous species have been pointed out in the literature. Thus, the objective of this work was evaluate the effects of N and Ca combination rates on the visual deficiencies of both nutrients, on the macronutrient status, chlorophyll content and nitrate reductase activity (RNO3-) taken on the recent expanded leaves of Jatropha curcas, as well as to evaluate N and Ca uptake and biomass yield during early plant growth, subjected to 2; 9; 16; 23 e 30 mmol L-1 N rates and 0.5; 1.75; 3.0; 4.25 e 5.5 mmol L-1 Ca rates, in the nutrient solution. Nitrogen, Ca and K concentrations on the recent expanded leaves were changed by N and Ca rates, whereas leaf-Mg concentrations ranged only by Ca supply. Increasing N and Ca rates in solution led to increased leaf area and the leaf biomass yield by 400% and 245%, respectively. On average, N and Ca taken up on leaves accounted for 29% and 39% of the plant uptake. Biomass yield is directly related to RNO3 - activity and chlorophyll content, and the range of N concentration in these leaves related to highest plant dry matter production is 43-45 g kg-1. In conclusion, N supply causes greater impact on the plant biomass yield; however, the effects are more relevant with increased Ca uptake.