Phosphorus analysis in soil under herbaceous perennial leguminous cover by nuclear magnetic spectroscopy

Abstract

-The availability and the reserves of organic phosphorus are controlled by its mineralization rate and are also influenced by changes in soil management. The objective of this study was to evaluate the influence of soil covering with different leguminous plant on soil organic P by 31 P-NMR spectroscopy. Alkaline soil extracts were obtained from two depths (0-5 and 5-10 cm) of an Ultisol cultivated with herbaceous perennial leguminous plants (Arachis pintoi, Pueraria phaseoloides, Macroptilium atropurpureum). In an adjacent area, samples of the same soil cover with a secondary tropical forest and grass (Panicum maximum) were also collected. The leguminous management was divided into with removal and without removal of shoot parts after cut on soil surface. Phosphate monoesters are the dominant P species in all soil samples and P diesters accumulated on the superficial layer of secondary forest soil. The P amount of this fraction is higher for the legume covered soil when compared with the grass covered soil. The permanence of leguminous plants on the topsoil after the cut promoted an increase in P diester/P monoester ratios. These findings can be accounted for an enhancement of P availability to plants in soils cultivated with leguminous plants.Index terms: cultivation, deforestation, cover crops. Análise de fósforo em solo com leguminosas herbáceas perenes por meio de ressonância magnética nuclearResumo -A disponibilidade e as reservas de fósforo orgânico são controladas pela taxa de mineralização e influenciadas pelas alterações no manejo do solo. O objetivo deste trabalho foi avaliar o fósforo orgânico mediante espectroscopia de ressonância magnética nuclear de 31 P (RMN 31 P) em solo sob cobertura de plantas leguminosas. Extratos alcalinos foram obtidos em duas profundidades (0-5 e 5-10 cm) de um Argissolo numa área cultivada com leguminosas herbáceas perenes (Arachis pintoi, Pueraria phaseoloides e Macroptilium atropurpureum). Em áreas adjacentes ao experimento foram coletadas amostras do mesmo solo sob cobertura de floresta tropical secundária (capoeira) e capim-colonião (Panicum maximum). O manejo das leguminosas foi dividido em com e sem a remoção da parte aérea da superfície após o corte das plantas. Os fosfatos em ligações monoésteres foram predominantes em todas as amostras de solo e os fosfatos em ligações diésteres foram acumulados na camada superficial do solo sob floresta secundária. A quantidade de fósforo em ligações diésteres foi maior nas amostras de solo sob cobertura de leguminosas do que sob gramíneas. A permanência da parte aérea na superfície do solo promoveu aumento na razão P diéster/P monoéster. Esses resultados podem ser usados para justificar o aumento da disponibilidade de fósforo para as plantas em solos cultivados com leguminosas.Termos para indexação: cultivo, desmatamento, culturas de cobertura do solo.

Desempenho de bananeiras consorciadas com leguminosas herbáceas perenes

“…No uso de plantas de cobertura do solo, mostra-se uma estratégia de manejo para os agroecossistemas, possibilitando aumentos de produtividade associados à otimização de processos biológicos (Espindola et al, 2006b). Entre as vantagens trazidas por essa prática, podem ser destacados a proteção do solo contra agentes climáticos causadores de erosão (Derpsch et al, 1991), o controle de plantas de ocorrência espontânea (Espindola et al, 2000) e o aumento da disponibilidade de nutrientes ligados à matéria orgânica do solo (Canellas et al, 2004).…”

Options for Improved Phosphorus Cycling and Use in Agriculture at the Field and Regional Scales

“…Monoesters, and particularly inositol phosphates, have long been considered to make up the majority of Po in soil, and because they readily sorb to soil surfaces they have been assumed to be less susceptible to mineralization (Condron et al, 1990; Turner et al, 2002; Giles et al, 2011). Certain diesters, including RNA and phospholipids, are thought to be relatively labile and readily mineralizable (Makarov et al, 2002; Canellas et al, 2004; Vincent et al, 2013; Cade‐Menun, 2017). The accurate quantification of monoesters and diesters has been challenging because some diester degradation occurs during sample analysis by NMR spectroscopy, especially the degradation of RNA and phospholipids (Makarov et al, 2002; Turner et al, 2003; Turner and Newman, 2005; Smernik et al, 2015; Cade‐Menun, 2015); however, this has been improved with correction protocols that can convert measured degradation products back into their original compounds and estimate concentrations more precisely (Schneider et al, 2016; Cade‐Menun, 2017; Abdi et al, 2019).…”

“…Recent studies have shown that diesters may make up significantly more soil Po than has been previously assumed (Vincent et al, 2013; Smernik et al, 2015; Schneider et al, 2016; Zhang et al, 2017). Greater diester concentrations have been correlated with uncultivated or perennial systems (Hawkes et al, 1984; Condron et al, 1990; Mahieu et al, 2000) and leguminous crops (Guggenberger et al, 1996; Canellas et al, 2004; Schneider et al, 2016), while the effect of P fertilization is unclear as varied results have been observed (McDowell et al, 2007; Schneider et al, 2016; Liu et al, 2017; Abdi et al, 2019). This illustrates that further research is required to understand how crop rotation and agroecosystem management may affect soil Po forms, so that through management we may be able to promote Po forms that are readily mineralizable and potentially increase P availability in low‐input systems at appropriate times.…”

Can tropical grasses grown as cover crops improve soil phosphorus availability?

“…The P o is mainly composed of orthophosphate monoesters (Stutter et al ., ), which can be classified as labile monoesters such as the breakdown products of DNA, and nonlabile monoesters such as inositol phosphates (Shears & Turner, ). Phytate is an inositol phosphate that can account for more than 70% of total P o (Canellas et al ., ), being the least bioavailable P o form due to its strong affinity to soil particles and fast precipitation as insoluble forms (Berg & Joern, ).…”