Evaluation of the Need for Copper with Several Soil Extractants¹

Abstract

Copper deficiencies have been observed in a number of crops grown on both organic and mineral soils in the Atlantic Coastal Plain. In order to recommend fertilization correctly, soil test calibrations are needed for the extractants used in the region. Soybeans (Glycine max), corn (Zea mays), and wheat (Triticum aestivum) were grown in the greenhouse on 15 soils fertilized with Cu at several rates. Percent maximum yield for the plant growth on each untreated soil was calculated from the dry matter produced. Four soil extractants were used: Double acid (DA); Mehlich‐Bowling (MB); Ammonium bicarbonate‐DTPA (AB); and Mehlich‐3 (M3). Percent maximum yield was expressed as a function of Cu released from the untreated soils by each extractant with a linear plateau model. The extractants performed similarly in explaining plant response, with each accounting for about 70% of the variation. The soil critical levels, determined by the junction of the response and the plateau portions of the surface, for DA, MB, AB, and M3 were similar among crops and averaged 0.26, 0.62, 0.53, and 0.37 mg L−1 Cu, respectively. Wheat and soybeans were also grown in the field on seven soils with two rates of Cu. Grain yields of the two crops were related to MB extractable Cu with the Cate‐Nelson method, which indicated a critical level of 0.70 mg L−1. Critical whole plant and leaf Cu concentrations were also determined. The critical whole plant Cu concentrations for soybeans, corn, and wheat, each grown 5 weeks in the greenhouse, were 3.8, 1.8, and 3.8 mg kg−1, respectively. Deficiency symptoms developed on corn and wheat at slightly lower values, 1.5 and 2.9 mg kg−1, respectively. In the field, the critical leaf concentrations at early flowering were 6 mg kg−1 for soybeans and 4 mg kg−1 for wheat.

Métodos de aplicação de cobre e avaliação da disponibilidade para a soja num Latossolo Vermelho-Amarelo franco-argilo-arenoso fase Cerrado

“…Assim, Makarim & Cox (1983) constataram que, de cinco locais, apenas dois revelaram resposta da soja à aplicação de 2,2 kg ha -1 de cobre a lanço, com aumentos de 14 e 10% no rendimento de grãos. Robertson et al (1973) obtiveram com a adição de 2,8 kg ha -1 de cobre no sulco de semeadura aumento de 180 kg ha -1 de grãos de soja.…”

“…A equação completa é dada por Y = A + BX, em que Y e X são os teores de cobre extraídos do solo (mg dm O nível crítico de cobre na folha foi de 3,9 mg kg -1 (Figura 2), estando abaixo do limite inferior das faixas de suficiência de 10 a 30 mg kg -1 (Malavolta et al, 1989) e de 5 a 20 mg kg -1 (Jones Jr., 1973) e do nível crítico de 6,0 mg kg -1 (Makarim & Cox, 1983), apesar de terem sido obtidos altos rendimentos de grãos (Quadro 1). Sugere-se, portanto, a realização de estudos de calibração para se definir melhor a faixa de suficiência de cobre na folha da soja.…”

“…No exterior, o número de trabalhos que avaliaram o efeito da aplicação de cobre no rendimento de grãos de soja também é reduzido (Sims & Johnson, 1991). Assim, Robertson et al (1973) obtiveram aumentos que variaram de 13 a 23% e Makarim & Cox (1983) constataram, em dois locais, aumentos de 14 e 10%. Na literatura consultada não se encontrou trabalho que avaliasse o efeito de métodos de aplicação de cobre no rendimento de grãos da soja.…”

Determination of Nutrient Availability and Elemental Toxicity by AB-DTPA Soil Test and ICPS

“…Cox (1987) in a review paper showed that soil properties other than the extractable level of micronutrients should be considered when soil test results are interpreted. Makarim and Cox (1983) found an R 2 value of 0.47 for AB-DTPA Cu and percent maximum yield using the Cate-Nelson analysis of variance method. This value was lower than the value for the Mehlic 1 test (R 2 = 0.70).…”

Nutrient status of potato grown on fine sandy loams in Prince Edward Island

“…Toxic Cu values for potatoes range from 17 -30 mg/kg (Mathur and Levesque, 1983;Trehan and Grewal, 1984). Mehlich 3 soil Cu levels of 0.4 mg/dm 3 are considered critical (Makarim and Cox, 1983).…”