D. J. Silva

Modelagem de funções no cálculo dos índices DRIS

O objetivo deste trabalho foi modelar o fator k e as funcoes DRIS para a diagnose foliar de mangueiras cultivadas. Dez pomares comerciais, no estagio de producao, localizados no vale do Rio Sao Francisco, foram monitorados, mensalmente, durante dois anos, por meio da coleta de amostras foliares para determinacao dos teores de N, P, K, Ca, Mg, B, Fe, Mn, Zn e Cu. Os dados foram testados quanto a normalidade e as relacoes entre as concentracoes dos nutrientes foram usadas para calcular as normas DRIS, obtendo-se media, variância e limites maximo e minimo de cada relacao dentro da populacao amostrada. Os nutrientes foram classificados como macronutrientes de resposta frequente (MAF) (N, P e K), macronutrientes de resposta rara (MAR) (Ca e Mg); micronutrientes de resposta frequente (MIF) (B, Fe, Mn e Zn) e, micronutrientes de resposta rara (MIR) (Cu). Funcoes DRIS foram desenvolvidas para cada classe de nutrientes. O modelo desenvolvido expressa o balanco nutricional das plantas cultivadas ajustado a cada nutriente e reflete o comportamento biologico das plantas como resultado da variacao da disponibilidade dos nutrientes.

Acurácia do diagnóstico nutricional de pomares de mangueiras obtido por três fórmulas DRIS

The objective of this work was to test the application of accuracy measures to determine the usefulness of nutritional diagnosis to compare different DRIS formulas, and to evaluate the use of these measures in the DRIS function modeling process. Three DRIS formulas were evaluated: bivariate relations (simplified); multivariate relations; and DRIS function modeling. Monitoring data from commercial mango orchards grown at Sao Francisco River Valley, Brazil, were used. Formula performances were evaluated based on the agreement of their diagnoses with the one provided by the sufficiency range method. Global accuracy, and the ones for insufficiency, equilibrium, excess, deficiency, sufficiency and nutritional toxicity were determined. The simplified and multivariate formulas showed similar results for insufficiency and deficiency accuracies, but they had a lower performance than the DRIS function modeling formula. This latter, for allowing of the adjustment of each DRIS function sensibility coefficient, showed to be promising in reducing the risks of false diagnosis for deficiency (as for not recommend the nutrient when it is necessary) and for insufficiency (as for recommend the nutrient when it is not necessary). However, the DRIS formula for function modeling does not show a satisfactory performance for other accuracy measures.

Nutritional balance and physiological disorders in mango 'Tommy Atkins'

With the objective of evaluating the effect of the nutritional balance on the incidence of physiological disorders in mango cv. Tommy Atkins, grown in Sao Francisco River Valley, a trial was carried out with fruits harvested at physiological ripening stage, classified as fruits without and with physiological disorder symptoms. From all of them, skin, flesh and pit were separated and dried in a stove at 65oC. This material was mineralized in order to determine N, K, Ca, Mg and B contents. Before dehydration, part of the flesh was taken for estimation of the total soluble solids (TSS) and total titrable acidity (TTA). The results allow to conclude that: high concentrations of Ca and Mg , as well as low ratios N/Ca and K/Ca, both in the flesh and in the skin, were efficient to prevent physiological disorders in mango fruits; the nutrient concentration in the skin may show better the condition of physiological disorders than the nutrient concentration in fruit flesh; and the TSS values and TSS/TTA ratio in fruits with symptoms were much higher than in fruits without symptoms, due to over ripening of flesh tissues.

GIRDLING AND GROWTH REGULATORS: EFFECTS ON THE BIOMETRIC MEASUREMENTS AND QUALITY OF BUNCHES OF VINE 'SUPERIOR SEDLESS'

Aiming to increase the berry size, weight of bunches and yield, the bunches of the cv. Superior Seedless was powdered with gibberelic acid (1 + 20 mg.L-1), bio-stimulant Crop Set® in the dosis of 0.1 and 0.2%. In adition was used the treatment known as girdling. Those treatments were applied in an isolated way or combined to each other. The work was carried out during 2001-2002 (two harvest seasons), in the Experimental Station of Bebedouro, Semi-arid Embrapa in Petrolina, Pernambuco State. The experimental design were in randomized blocks with 12 treatments and three replications. The differences among the treatments were not statistical significant in the two evaluated seasons. However, when the gibberelic acid was associated with Crop Set® 0.1% and girdling, it was observed a tendency to increase the weight of bunches, as well as, the weight and berry size in the 2001 season. The bunches treated with gibberelic acid presented stronger rachis, although significant differences are not observed among the treatments. Some plants submited to the girdling presented problems with cicatrization, that caused death of them, recomending to avoid this practice in the conditions of this work.

Composto orgânico em mangueiras (Mangifera indica L.) cultivadas no semiárido do nordeste brasileiro

The objective of this study was to evaluate the soil chemical characteristics, the nutrient contents in leaves and the production of mango crops grown in the organic system. An experiment was carried out with three composts named A, B and C, using three levels (0, 5 and 10 t ha-1) of each compost in a commercial production of mango on organic cultivation. The experiment was carried out in a randomized block design, 3 x 3 factorial (3 composts x 3 levels) and three replications. The organic composts were prepared with animal and vegetable waste, enriched with castor bean, MB4® and thermo phosphate. The enrichment was efficient in increasing the content of nutrients in composts. The organic composts increased the levels of soil organic matter (SOM), especially in the compost C, whose soil analysis showed higher levels of total P, K, Ca, Mg, B, Cu, Mn and Zn. The SOM increased linearly with the enhancement of the compost levels. Production and fruit number per plant were higher with the use of the B and C composts, which showed higher contents of total nutrients. The compost levels provided a linear increase in N leaf content. The production of fruit (kg ha-1) and fruit number per plant showed quadratic increase with the compost concentrations, without presenting a maximum point.

Assessment on nutrient levels in the aerial biomass of irrigated guava in São Francisco Valley, Brazil

A aplicacao de fertilizantes em culturas perenes baseia-se na reposicao das quantidades de nutrientes removidas pelos frutos, mas a imobilizacao de nutrientes deve ser tambem considerada. Assim, foram determinadas as concentracoes de nutrientes nas folhas e nos frutos da goiabeira cv.Paluma, irrigada, em Petrolina-PE, bem como as quantidades de nutrientes removidas pelos frutos e pela poda de frutificacao do ciclo seguinte. Entre os macronutrientes, o N e o K foram os mais removidos pelos frutos, enquanto o Fe , o Zn e Mn apresentaram maiores valores entre os micronutrientes. No minimo, 60% das quantidades totais de N,P,K,Fe e B removidas pela poda estavam imobilizadas na folha e no fruto nao-comerciavel.

Cultivo de melão orgânico: fosfatos naturais como fontes alternativas de fósforo

Aiming to evaluate the efficiency of natural phosphates in melon organic cropping under irrigation, two experiments were carried out in Petrolina-PE, one in a Yellow Argisol (PA) and other in a Grey Argisol (PAC). The evaluated treatments were: 1 - without P, 2 - 50 kg ha-1 of P2O5 as triple super phosphate (TS), 3 - 100 kg ha-1 of P2O5 as TS, 4 - 150 kg ha-1 of P2O5 as TS, 5 - 100 kg ha-1 of P2O5 as thermo phosphate, 6 - 100 kg ha-1 of P2O5 as natural phosphate of Gafsa and 7 - 100 kg ha-1 of P2O5 as natural phosphate Fosbahia. The melon crop showed similar responses to the P application in both soils, whose maximum productivities of 26.00 t ha-1 and 25.46 t ha-1 were obtained with 107.6 kg ha-1 and 118.6 kg ha-1 of P2O5 in PA and PAC, respectively. The efficiency of thermo phosphate, phosphate of Gafsa and Fosbahia in relation to TS assumed the sequence of 86.2%, 77.1% and 71.9% in PA and 101.5%, 72.3% and 67.3% in PAC. These results suggest that thermo phosphate is the most appropriated phosphate source to be used in the melon organic cropping. It is necessary 843.12 kg of thermo phosphate to produce 25 t ha-1 of melon fruit that represent 3.4% of the production cost.

Efeito de fosfatos naturais em plantas de melão cultivadas em vasos.

Organic agriculture is an emerging activity in the upper mid Sao Francisco River Valley, requiring technologies that are in line with the principles of this agricultural system. A study was carried out at Embrapa Semi-Arido to evaluate the efficacy of natural phosphates applied to three regional soils (dystrophic Grey Argisol - PAGd, eutrophic Yellow Argisol - PAe and Vertisol - V) planted with melon (Cucumis melo) in pots accommodated on wooden benches. The factorial treatments (3 x 4) + 1 consisted of three phosphorus levels (40, 80 and 160 mg dm-3 P2O5), four phosphorus sources (triple superphosphate-ST, thermophosphate-TM, Gafsa natural rock phosphate-FG and Fosbahia natural phosphate-FB) and a control treatment without phosphorus, in a completely randomized design with three replications. Each soil represented a trial. Shoot dry matter (DM), P plant content and P soil concentration extracted by Mehlich-1 and anionic exchange resin (AER) were evaluated 38 days after planting. In V and PAGd soils the phosphates were less effective than in PAe soil. TM was the P source with the highest efficiency for DM production in the three soils (56 to 100 % in relation to triple super phosphate). In PAe, FG also presented relatively high efficiency, equivalent to 80 % of that obtained with triple super phosphate. The Mehlich-1 and AER extractors were equally effective at evaluating P availability.

Transporte de fósforo e de potássio em colunas com agregados de um latossolo vermelho distrófico

The objective of this work was to compare the diffusive-dispersive coefficients of phosphorus and potassium as well as to describe nutrient transport in different aggregate classes of a typic Haplortox, cultivated with maize over several years, by applying two theoretical models. The experiment was carried out using percolation columns and five classes of aggregate sizes (2.0-1.0, 1.0-0.5, 0.5-0.25, 0.25-0.105 and < 0,105 mm). The elution column consisted of a glass column with 2 cm internal diameter and 30 cm length, filled up with aggregates until 10 cm from the upper boundary. All columns were saturated with a 0.005 mol L-1 CaCl2 solution, under vacuum. The velocity of the effluent was controlled and kept near that obtained for the smallest aggregate class. The saturation solution was applied until reaching a steady flow. Then a slug of a 0.05 mol L-1 KH2PO4 (Co) solution was applied. In the collected effluent, concentration of phosphorus and potassium (C) was determined, which permitted to obtain the C/Co ratio as a function of the pore-volume number of the percolated solution. This allowed to obtain the experimental curve for these elements, which was compared with the theoretical breakthrough curves estimated by the two models; one of them considers only the dispersive transport while the other one considers the diffusive-dispersive transport. The diffusive-dispersive coefficient was higher for potassium than for phosphorus in those classes with greater-diameter aggregates. The opposite occurred in the smallest classes, which indicates that phosphorus moved faster than potassium in those aggregate columns, under the studied conditions. The model accounting only for the dispersive flow presented a better prediction for phosphorus and potassium transportation in all aggregate classes. The theoretical curves showed a better description for potassium than for phosphorus transport.

Fluxo de massa e difusão de enxofre para raízes de milho em solos ácidos de Minas Gerais

A greenhouse experiment was carried out during the period October, 1991 to December, 1992, to evaluate the mass flow and diffusion contributions on sulphur transport to corn roots in soil surface samples (0-20 cm) of three acid soils collected in Vicosa, Paracatu and Lassance, Minas Gerais State, Brazil. Originally, the soil samples presented 5.0, 1.2 and 1.4 mg dm-3 of available S, respectively, obtained by extraction with a Ca(H2PO4)2 solution containing 500 mg L-1 of P in HOAc 2 mol L-1 solution. A 3 x 5 factorial layout was used with three soils and five sulphur levels (0, 20, 40, 80 and 160 mg dm-3), arranged in randomized complete block design, with four replications. Tensiometers controlled the soil water potencial in each pot and it was mantained at approximately -10 kPa. The mass flow contribution was calculated multiplying sulphur concentration on soil saturation extract by volume of transpired water. The difference between total sulphur absorved and mass flow contribution was assumed to be due to diffusion contribution. Mass flow was the main process of sulphur transport to corn roots. At high sulphur concentration in soil solution, the sulphur quantities supplied by mass flow were higher than those required by plants. Diffusion process contributed to sulphur transport only at low sulphur concentration in soil solution.