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Plant availability of phosphorus in the neutral ammonium citrate fraction of Brazilian acidulated phosphates (1998)

Prochnow, L.I. ; Kiehl, J.C. ; van Raij, B.

Springer

Nutrient cycling in agroecosystems 52 (1998), S. 61-65

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ISSN: 1573-0867

Keywords: acidulated phosphates ; available P ; cationic impurities ; corn ; phosphorus sources ; water soluble P ; Zea mays

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract In Brazil, where the rock phosphates are high in impurities, no attempthas been made to evaluate the P supplying efficiency of the neutral ammoniumcitrate fraction (NAC) of P fertilizers, or to verify if the NAC +H2O extraction solution (AOAC) is satisfactory for estimatingthe P availability. To attain these objectives, a greenhouse experiment wascarried out with samples of a Typic Hapludox soil. Four acidulatedphosphates obtained from Brazilian raw materials were studied; monocalciumphosphate p.a.[Ca(H2PO4)2·H2O]was included as a standard source of P, as well as leached samplescontaining no water-soluble P. The fertilizers were thoroughly mixed withthe whole soil in the pots or with only 1% of its volume, at the rateof 50 mg kg-1 of P, soluble in NAC + H2O. Cornplants (Zea mays, L.) were grown for 35 days and the amounts of dry matterand P accumulated in plant tops were determined. Increasing the amount ofcationic impurities in the raw materials decreased the concentration ofwater-soluble P, NAC + H2O-soluble P and water-soluble P/NAC+H2O soluble P ratio of the fertilizers obtained. The P in theNAC fraction was not as much available to plants as in the NAC +H2O fraction or in pure MCP. The great variation found in drymatter (5.4 to 17.1 g pot-1) and in P uptake (6.3 to 22.2 mgpot-1) indicates that the AOAC method is not an adequate indexfor evaluating the P availability of fertilizers with high amounts ofcationic impurities.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1016335612914

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Phosphorus and potassium soil test and nitrogen leaf analysis as a base for citrus fertilization (1998)

Quaggio, J. A. ; Cantarella, H. ; van Raij, B.

Springer

Nutrient cycling in agroecosystems 52 (1998), S. 67-74

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ISSN: 1573-0867

Keywords: citrus ; soil analysis ; leaf analysis ; calibration ; fertilizer response ; fertilizerrecommendation

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract 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.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1009763027607

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Calcium sulphate, phosphogypsum and calcium carbonate in the amelioration of acid subsoils for root growth (1997)

Carvalho, M.C.S. ; van Raij, B.

Springer

Plant and soil 192 (1997), S. 37-48

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ISSN: 1573-5036

Keywords: Al toxicity ; Ca deficiency ; maize ; phosphogypsum ; root growth ; subsoil acidity

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract The chemical barrier to root development existing in the subsoils of acid soils is a subject of increasing interest. In order to better understand the factors involved in the amelioration of subsoil acidity, the effects of calcium sulphate, phosphogypsum and calcium carbonate on the properties of the solid and liquid phases of subsoil samples and on the growth and nutrient uptake by maize (Zea mays L.) were evaluated. The soils used were two alic red-yellow latosols, two acric dusky red latosols and one alic dark-red latosol from the State of São Paulo, Brazil. A vertical split-root technique was used in a greenhouse experiment, with the plants initially grown in a small pot with 130 g fertile soil, which was introduced in a larger pot containing 2 dm3 of the subsoil samples. The treatments consisted of a control (C) and applications of calcium carbonate (CC), calcium sulphate (CS) and phosphogypsum (PG) at the rate of 10 mmolc Ca2+ dm-3. CS and PG reduced soil acidity, but in a much smaller proportion than CC. Calcium carbonate reduced the activity of Al3+ because of the increase in pH. Total aluminum and calcium contents in the soil solution were much higher for the red-yellow latosols than for the other soils, indicating lower sorption of Ca2+ and $$SO_4^{2 - } $$ in these soils. The activity of Al in the soil solution was decreased in different ways for the five soils, depending on the ionic strength and the formation of the ionic pair $$AlSO_4^ + $$ and, in the case of PG, the formation of complexes of Al with F (AlF2+, $$AlF_2^ + $$ and $$AlF_3^\bigcirc $$ ). The subsoil samples presented severe restrictions for maize root growth and all three treatments were equally effective in increasing root development, which could be attributed to the supply of calcium in one of the acric dusky red latosols and a combined effect of the amendment in reducing the activity of Al and increasing the activity of Ca in the soil solution in the other soils. As a consequence the three treatments increased in the same manner water, N and K uptake from the subsoil and the dry matter production of maize. It can be concluded that, for the soils considered in this research, phosphogypsum is an effective amendment for acid subsoils containing low calcium or toxic aluminum contents.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1004285113189

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