Potassium Removed from Some Southern Brazilian Soils by Exhaustive Cropping and Chemical Extraction Methods

Abstract

Soils from the orders Alfisol, Inceptisol, Mollisol, Ultisol, and Oxisol contained exchangeable K (neutral 1N NH4OAc) and boiling 1N HNO3 extractable K varying from 31 to 358 ppm and 62 to 652 ppm, respectively. Total K varied from 1,780 to 14,200 ppm. Quantities absorbed from each soil by 7 cuttings of perennial ryegrass (Lolium perenne) in the greenhouse ranged up to 13 times that of exchangeable K and up to 5 times that of HNO3‐extractable K. Total plant uptake represented 3.5 to 29.7% of total soil K. In no soil did K become limiting in the first four cuttings. However, except for the Mollisols, uptake decreased abruptly in the later cuttings, indicating very little “slowly” available K. Even though exchangeable K and K removed by strong acids were highly correlated with plant uptake (r = 0.744** to 0.881**), all extractants greatly underestimated actual plant‐available K under intensive cropping. Total soil K did not significantly correlate with plant uptake (r = 0.211).

The potassium paradox: Implications for soil fertility, crop production and human health

“…Initial recoveries were three-to fivefold higher for non-exchangeable than exchangeable K, followed by a gradual decline toward a stable level of 240-300 kg ha − 1 , with approximately 3000 kg ha − 1 as the cumulative recovery of non-exchangeable K. The resilient behavior of soil K is further revealed, in that 4 years of crop K removal had no consistent effect on soil concentrations of exchangeable, non-exchangeable or total K, implicating the mineral fraction as an important source of buffering. These findings are to be expected, considering what has long been known about the availability and dynamics of non-exchangeable and mineral K, based on chemical extraction 19,[85][86][87] (see also supplemental references [22] and [27][28][29][30] for the online version of the paper), exhaustive cropping 81,86,88,89 (see supplemental references [8], [15] and [16] for the online version of the paper) and electrodialysis 83,90 .…”

Nível crítico e resposta das culturas ao potássio em um Argissolo sob sistema plantio direto

“…Isto parece indicar que a recomendação da adubação potássica está desbalanceada, visto que, enquanto 73,1 % das amostras apresentaram teores acima do nível crítico de K, apenas 20,5 % mostraram-se suficientes em fósforo, contra 49,3 e 23,6 %, respectivamente, emNa Região Sul do Brasil, vários trabalhos de pesquisa estudaram a contribuição de diferentes formas de potássio do solo e suas interações na disponibilidade desse nutriente às plantas (Oliveira et al, 1971;Silva & Meurer, 1988;Meurer & Anglinoni, 1993;Melo et al, 1995;Silva et al, 1995;Meurer et al, 1996;Castilhos & Meurer, 2002;Melo et al, 2004). A estimativa das formas de potássio tem sido realizada com cultivos sucessivos de plantas (Mielniczuk & Selbach, 1978;Patella, 1980;Nachtigall & Vahl, 1991a) químicos (Nachtigall & Vahl, 1991b).…”

Efeito residual da adubação potássica do azevém sobre o arroz subseqüente em plantio direto

“…Isto significa que aproximadamente metade do potássio acumulado na parte aérea da cultura na ausência de adubação potássica foi proveniente de formas de K inicialmente não detectadas pelo Mehlich-1. Esta contribuição de K não computado pelo Mehlich-1 foi verificada em outros trabalhos (Oliveira et al, 1971;Lopes et al, 1995;Natale et al, 1996;Espinal, 1997;Simonete et al, 1998), explicando, pelo menos em parte, a ausência de resposta da cultura à adubação potássica neste solo. …”