Modifications of phosphorus in Latosol as a function of humic acids and acidity

Abstract

Palavras-chave:fosfato sorção substâncias húmicas A B S T R A C TThe effect of humic acids (HA) on phosphorus (P) availability is still contradictory; thus, it is necessary to identify the conditions that play a crucial role in this effect. The aim of this study was to investigate the effect of HA application, combined with doses of P, on the content of this nutrient in a Latosol with and without acidity correction. Two experiments were carried out, one with HA from peat and another with HA from mineral charcoal (leonardite). Doses of these acids (0; 1.12 and 5.62 mg C g -1 of soil) and P (26.2 and 104.7 mg P g -1 of soil, 1 and 4-fold higher than recommended, respectively) were tested at soil pH 4.5 and 7.0, in a three-factorial design. The soil was incubated for 20 days and the soil-P content was measured by Mehlich-1 and remaining-P tests. The effect of HAs on P availability varied with the P doses and soil acidity. Humic acids application increases P content in Latosol when P dose is higher than recommended and there is no acidity correction (pH 4.5). However, there is no effect of HAs application on soil-P content when applying the recommended amount of this nutrient, irrespective of the pH value.Modificações de fósforo em Latossolo em função de ácidos húmicos e acidez R E S U M O O efeito de ácidos húmicos (AH) na disponibilidade de fósforo (P) ainda é contraditório. Assim, é necessário identificar as principais condições que podem influenciar esse efeito. Com o trabalho, objetivou-se investigar o efeito da aplicação de AH, combinada com doses de P, no teor desse nutriente em Latossolo com e sem correção de acidez. Foram conduzidos dois experimentos, um com AH extraído de turfa e outro com AH extraído de carvão mineral (leonardita). Doses desses ácidos (0; 1,12 e 5,62 mg C g -1 de solo) e de P (26,2 e 104,7 mg P g -1 de solo, 1 e 4 vezes maior que o recomendado, respectivamente) foram testadas, em dois valores de pH do solo (4,5 e 7,0), em esquema trifatorial. O solo foi incubado por 20 dias e os teores de P foram extraídos com os métodos Mehlich-1 e P remanescente. O efeito dos AHs na disponibilidade desse nutriente variou com as doses de P e o pH do solo. A adição desses ácidos aumenta o teor desse nutriente em latossolo somente quando a dose de correção de P for maior que a recomendada e a acidez (pH 4,5) não for corrigida. Por outro lado, os AHs não influenciam o teor desse nutriente quando a dose de correção aplicada corresponder à quantidade recomendada, independentemente do pH do solo.

Accumulation of humic substances in an Oxisol fertilized with pig slurry for 15 years

“…Ventura et al (2018) observed improvements in soil quality caused by increases in SOC, mainly HS in HU and FA fractions evaluated in biogenic aggregates. Beck et al (2018) found higher P availability in soils with application of P at rates higher than that recommended, combined with HU, in soil with pH 4.5. Organic compounds affect microbial activity and nutrient availability in the long-term (Dall'Orsoletta et al, 2018).…”

Enhanced Phosphorus Release from Phosphate Rock Activated with Lignite by Mechanical Microcrystallization: Effects of Several Typical Grinding Parameters

“…In the ultrafine pulverization of phosphate minerals, the addition of a high surface-reactive P activator such as lignite plays an important role in improving the product performance [13]. The positive effect of humic acid by lignite addition was confirmed by the generation of effective P applied to the soil [14]. Lignite humic acid was used to modify PR powder to prepare humic acid-activated phosphate fertilizer.…”