J. A. Quaggio

Extraction of phosphorus, potassium, calcium, and magnesium from soils by an ion-exchange resin procedure

Abstract A procedure for the simultaneous extraction of phosphorus, potassium, calcium and magnesium from soils, by an ion‐exchange resin procedure applicable to large‐scale advisory soil testing, is described. The important steps are the disaggregation of soil by shaking in water during 15 minutes with a glass marble, the transference of the elements from the soil to a sodium bicarbonate treated mixture of anion and cation exchange resins during a 16‐hour shaking period, the separation of the resin from the soil by sieving and extraction of the elements from the resin. The results of resin extractable calcium, magnesium and potassium were comparable to the results of these elements extracted with 1M NH4OAc, to calcium and magnesium extracted with 1M KCl, and to potassium extracted with 0.025M H2SO4. For phosphorus the resin extractable values were not comparable to the results obtained by the former routine method, based on the extraction with 0.025M H2SO4. The results of resin extractable P presented cl...

Ammonia volatilisation from urease inhibitor-treated urea applied to sugarcane trash blankets

Restricoes legais a colheita de cana-de-acucar com despalha a fogo estao causando um aumento da area cultivada com cana crua. Essa pratica gera uma espessa camada de palha de cana sobre o solo apos a colheita, o que dificulta a incorporacao de fertilizantes. Uma vez que grandes quantidades de amonia podem ser perdidas quando a ureia e aplicada superficialmente sobre a palha, e importante buscar alternativas para maximizar a eficiencia de uso do N-ureia. O inibidor de urease NBPT retarda a hidrolise da ureia e pode contribuir para diminuir as perdas de amonia por volatilizacao. Para quantificar essas perdas, foram instaladas câmaras coletoras de amonia em sete areas de producao de cana-de-acucar colhida sem queima; estas foram fertilizadas com sulfato ou nitrato de amonio, ureia ou ureia tratada com NBPT. Todos os fertilizantes nitrogenados foram aplicados superficialmente em doses de 80 ou 100 kg ha-1de N. As perdas de N foram muito pequenas quando se usou nitrato ou sulfato de amonio. Entretanto, as perdas por volatilizacao de amonia decorrentes do uso de ureia variaram de 1% (com dias chuvosos apos a adubacao) a 25% do N aplicado. O uso de NBPT proporcionou reducoes de 15 a 78% nas perdas por volatilizacao, dependendo das condicoes climaticas nos dias posteriores a aplicacao de N. A adicao de NBPT a ureia ajudou a controlar as perdas de amonia, mas o inibidor foi menos efetivo quando chuvas suficientes para incorporar a ureia no solo ocorreram somente 10 a 15 dias, ou mais, apos a aplicacao dos fertilizantes.

Fruit yield of Valencia sweet orange fertilized with different N sources and the loss of applied N

Nutrient management recommendations are needed to increase nitrogen uptake efficiency, minimize nutrient losses and reduce adverse effects on the environment. A study of the effects of nitrogen fertilization on N losses and fruit yield of 6-yr-old Valencia sweet orange (Citrus sinensis (L.) Osb.) on Rangpur lime rootstock (C. limonia Osb.) grove was conducted in an Alfisol in Brazil from 1996 to 2001. Urea (UR) or ammonium nitrate (AN) fertilizers were surface-applied annually at rates of 20, 100, 180, and 260 kg N ha−1 split into three applications from mid-spring to early fall. A semi-open trapping system, using H3PO4 + glycerol-soaked plastic foams, was used for selected treatments in the field to evaluate NH3 volatilized from applied N fertilizers. Ammonia volatilization reached 26 to 44% of the N applied as UR at the highest rate of N used. Ammonia volatilization losses with AN were lower (4% of the N applied). On the other hand, AN resulted in greater nitrate leaching and greater soil acidification than UR. A marked effect of AN fertilizer on soil pH (CaCl2) in the 0–20 cm depth layer was observed with a decrease of up to 1.7 pH units at the highest N rate. Acidification was followed by a decrease in exchangeable Ca and Mg; consequently, after 5 yr of fertilization with AN, soil base saturation dropped from 77% in the plots treated with 20 kg N ha−1 per year, to 24% in those that received 260 kg N ha−1 per year. The effect of N sources on fruit yield varied from year to year. In 2001, for a calculated N application rate of 150 kg ha−1, the fertilizer efficiency index of UR was 75% of that of AN.

Alternative use of the SMP‐buffer solution to determine lime requirement of soils

Abstract A close relationship was found between the pH of soil suspensions in the SMP buffer solution (pHsmp) and the potential acidity of soils (H + Al) extracted by a neutral calcium acetate solution (r = 0.98), for twenty six soil samples of the State of Sao Paulo, Brazil, This relationship was represented by the equation lnY = 7.76 ‐ 1.053X, which allowed for the calculation of H + Al directly from the values of pHsmp. With the values of H + Al and the sum of bases, calcium, magnesium and potassium, the cation exchange capacity (CEC), and the base saturation (V) were calculated. Relationships between the base saturation of the soils and the active acidity of soil suspensions were close, both for pH determined in water (r=0.94) and pH determined in 0.01M CaCl2 solution (r ‐ 0.97). Thus the lime requirement (LR) of soils could be calculated, for given values of pH or base saturation, using the equation LR = CEC (V2 ‐ V1)/100, in which V1 is the base saturation of the soil and V2 is the expected value up...

Nutrient content of biomass components of Hamlin sweet orange trees

ABSTRACT: The knowledge of the nutrient distribution in trees is important to establish sound nutrientmanagement programs for citrus production. Six-year-old Hamlin orange trees [ Citrus sinensis (L.) Osb.] onSwingle citrumelo [ Poncirus trifoliata (L.) Raf. x Citrus paradisi Macfad.] rootstock, grown on a sandy Entisolin Florida were harvested to investigate the macro and micronutrient distributions of biomass components.The biomass of aboveground components of the tree represented the largest proportion of the total. Thedistribution of the total tree dry weight was: fruit = 30.3%, leaf = 9.7%, twig = 26.1%, trunk = 6.3%, and root =27.8%. Nutrient concentrations of recent mature leaves were in the adequate to optimal range as suggestedby interpretation of leaf analysis in Florida. Concentrations of Ca in older leaves and woody tissues weremuch greater than those in the other parts of the tree. Concentrations of micronutrients were markedly greaterin fibrous root as compared to woody roots. Calcium made up the greatest amount of nutrient in the citrus tree(273.8 g per tree), followed by N and K (234.7 and 181.5€g€per€tree, respectively). Other macronutrientscomprised about 11% of the total nutrient content of trees . The contents of various nutrients in fruits were: N= 1.20, K = 1.54, P = 0.18, Ca = 0.57, Mg = 0.12, S = 0.09, B = 1.63€x€10

PHOSPHORUS AND POTASSIUM SOIL TEST AND NITROGEN LEAF ANALYSIS AS A BASE FOR CITRUS FERTILIZATION

A network of six NPK long-term field trials was carried out on different soils of citrus-producing regions of São Paulo state, Brazil, in order to estimate quantitative relations of fruit yield to NPK fertilization and to determine parameters for fertilizer recommendation based on soil testing and leaf analysis. The experiments were set up in an incomplete factorial design 1/2 43 with 32 treatments, with four yearly rates of N (30, 100, 170 and 240 kg N/ha), P (9, 27, 45 and 63 kg P/ha) and K (25, 91, 157 and 223 kg K/ha). Four to seven harvests were recorded for the six experiments. Response surfaces of the type y = bo + b1N + b11N2 + b2P + b22P2 + b3K + b33K2 + b12NP + b13NK + b23PK were adjusted to the average yields of each trial. Correlation were established for yield increases, expressed as relative yields, and results of soil analysis of P and K, and leaf analysis of N. Soil samples taken at 0-20 cm depth in the beginning of each experiment were analyzed for resin extractable P and exchangeable K using an ion-exchange resin procedure. Yield responses for phosphorus and potassium applications were observed respectively in soils with less than 20 mg dm-3 of P and 20 mmolc dm-3 of K+. Yield responses to nitrogen were related to the total content of nitrogen in leaves, being largest for N values of 23 g kg-1 and smallest for N of 28 kg-1. With these field information, a practical approach for fertilizer recommendation for citrus, based on soil analysis for P and K and leaf analysis for N, was developed.

Calagem para a cana-de-açúcar e sua interação coma adubação potássica

SUGARCANE RESPONSE TO LIMING AND POTASSIUM FERTILIZATION Six experiments were carried out in the main sugarcane regions of the State of Sao Paulo, Brazil, in order to study sugarcane response to liming and potassium and its interactions. The treatments consisted of four rates of liming and tree rates of potassium, setup in factorial experiments, summing up twelve treatments, with four replications, organized in randomized block design. In four sites, the experiments were conducted during the first season and in two others, the ratoons were also evaluated. Four sites were cropped with the variety SP70-1143 and in the others, the varieties SP71-6163 and SP71-1406 were planted. Despite the high soil acidity in all sites, the response of sugarcane to liming was significant only in two sites, showing high tolerance of planted varieties to soil acidity conditions. The sugarcane response to potassium was linear in seven out of the 10 evaluated seasons. Significant interactions between liming and potassium were not observed in any studied site.

Soil and plant analyses for lime and fertilizer recommendations in Brazil

Abstract The fertilizer recommendation guidelines for over 160 crops for the State of Sao Paulo, Brazil were updated in 1996 based on recent results of research on soil and plant analysis, and crop responses. Recommendations are based mainly on soil analysis and expected yield. Limestone rates are calculated to raise soil base saturation as a percentage of the cation exchange capacity (CEC) of the soil at pH 7.0, to levels which vary with crop species (i.e., to 50% for rice, coffee, and cassava, 60% for sugar cane and soybeans, 70% for cotton and maize, and 80% for grapes and onions). In addition, exchangeable magnesium (Mg) contents must reach a minimum level. Exchangeable subsoil aluminum (Al) and calcium (Ca), and clay content are used to determine rates of gypsum as amendment of subsoil acidity. Fairly consistent data on soil phosphorus (P) and potassium (K) calibration are available for Brazilian soils. Potassium rates are recommended based on values of soil exchangeable K and, for P fertilization, i...

Response of Young Citrus Trees on Selected Rootstocks to Nitrogen, Phosphorus, and Potassium Fertilization

ABSTRACT The majority of the citriculture in Brazil is located in the state of São Paulo, with a total production area of 700,000 ha. Trees are grafted mostly on ‘Rangpur’ lime (RL; Citrus limonia Osbeck) rootstock. Despite its good horticultural performance, use of other rootstocks has increased with the search for disease-tolerant varieties to improve grove productivity and longevity. Furthermore, there is a lack of information on young tree response to fertilization, and optimal nutrient requirements of different scion/rootstock combinations for maximum fruit yield. A network of field experiments was conducted to study the differential response of young sweet orange trees on selected rootstocks to nitrogen (N), phosphorus (P), and potassium (K) fertilization. The application of soil and leaf analyses to develop optimal fertilizer recommendations was evaluated. Experiments were conducted in three locations using fractional factorial design of one-half (4 × 4 × 4) type with four rates of N, P, or K calculated to be applied for five years after tree planting. Fruit yield response was evaluated during the last two years and correlated with soil and leaf analyses data. The trees on RL rootstock demonstrated increased efficiency of nutrient use and fruit production compared with those on ‘Cleopatra’ mandarin (CL; C. reshni hort. ex Tanaka) or ‘Swingle’ citrumelo [SW; Poncirus trifoliata (L.) Raf. × C. × paradisi Macfad.] rootstocks. The trees on SW rootstock appeared to require greater N and K rates than those on RL rootstock. Phosphorus requirement was greater for ‘Natal’ or ‘Valencia’ trees on CL than on RL rootstock. These results will become the basis for revising current fertilizer recommendation guidelines for young trees in Brazil.

Extractable phosphorus availability indexes as affected by liming

Abstract In acidic soils, with high contents of Fe and Al oxides, the effect of liming in increasing P availability to plants has been observed for years. However, commonly used soil tests often fail to show increases in soil P due to liming. This subject was investigated using soil samples and results of leaf analysis of four liming experiments with soybeans, sunflower and beans. Soil P was extracted with the Mehlich I (0.05 N HCl + 0.025 N H2SO4), the Bray‐Kurtz (0.03 N NH4F + 0.025 N HCl), and the Olsen solutions (0.5 N NaHCO3 at pH 8.5), and by an ion‐exchange resin procedure. Leaf analysis indicated significant increases in P content due to liming. However, soil P was unaffected when determined by the Mehlich I and the Bray‐Kurtz methods, whereas the results by Olsens method were unaffected in two cases and decreased with increases in soil pH in the two other experiments. The results of resin‐extractable P were related to leaf content of P, increasing with liming, demonstrating the superiority of th...