Phosphorus fractionation in a sandy soil under organic agriculture in Northeastern Brazil (original) (raw)
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Organic Phosphorus Fractions in Soil Fertilized with Cattle Manure
Revista Brasileira de Ciência do Solo, 2015
Inorganic phosphorus (Pi) usually controls the P availability in tropical soils, but the contribution of organic P (Po) should not be neglected, mainly in systems with low P input or management systems that promote organic matter accumulation. The aims of this study were to evaluate the changes in the Po fractions over time in soil fertilized and not fertilized with cattle manure and to correlate Po forms with available P extracted by anion exchange resin. The experiment was carried out under field conditions, in a sandy-clay loam Haplustox. The experimental design was a 2 × 9 randomized complete block factorial design, in which the first factor was manure application (20 t ha-1) or absence, and the second the soil sampling times (3, 7, 14, 21, 28, 49, 70, 91, and 112 days) after manure incorporation. Labile, moderately labile and non-labile Po fractions were determined in the soil material of each sampling. Manure fertilization increased the Po levels in the moderately labile and n...
Soil Organic Matter as Affected by Green Manure at Brazilian Conditions
The use of green manure has been associated with increasing soil organic matter (SOM), which is an essential component of high-quality agricultural soils, especially in tropical environments such as Brazil. The aim of this review was to present evidence of the effectiveness that green manures use has on the improvement of Brazilian SOM stocks. The contribution of soil aggregation to SOM stabilization, the importance of returning high amounts of plant residues to the soil, and the effectiveness of including N-fixing legumes in the cropping systems are all summarized. Soil aggregation is highly dependent on the continual addition of crop residues to the soil, and creates favorable conditions for SOM accumulation. SOM build-up is directly correlated to the amount of crop residues added to the soil and it is closely dependent on the duration, in the long-term, of this soil residue input. Moreover, the quality of these crop residues is of major importance, considering not only the high content of C directly added to the soil by the green manures, but also their N content, which is a determinant in the growth of subsequent crops, resulting in increased amounts of residue-derived C returned to the soil. The inclusion of green manures in cropping systems, especially legume species, in association with appropriate soil management practices, is a feasible and sustainable way to increase long-term SOM stocks in Brazilian tropical conditions.
Agronomy
The input of organic matter in the soil by the no-tillage system (NTS) increases as the system becomes established, raising the levels of organic phosphorus (P) and reducing the P soil adsorption. This study evaluated the availability of organic and inorganic P in areas under different management systems and stages of adoption in the Cerrado. The data were analyzed as a completely randomized design, corresponding to: (1) an NTS after 5 years of its implantation (NTS5); (2) an NTS after 17 years of its implantation (NTS17); (3) a conventional tillage system more than 20 years old (CTS); (4) Native Cerrado (NC). There were five repetitions for all treatments. Depths of 0–5 and 5–10 cm were evaluated for the available P (P-avail), remaining P (P-rem), organic P (oP), and inorganic P (iP) forms extracted with Sodium bicarbonate (NaHCO3) (P-avail), Sulfuric acid (H2SO4) (moderately labile), and Sodium hydroxide (NaOH) (moderately resistant). The P from the sequential extractions accumula...
Agronomy, 2021
Understanding phosphorus (P) dynamics in tropical sandy soil treated with organic residues of contrasting quality is crucial for P management using organic amendments. This research determined P fractions in a tropical sandy soil under the application of organic residues of different quality, including groundnut stover (GN), tamarind leaf litter (TM), dipterocarp leaf litter (DP), and rice straw (RS). The organic residues were applied at the rate of 10 t DM ha−1 year−1. The P fractions were examined by a sequential extraction procedure. Organic residue application, regardless of residue quality, resulted in P accumulation in soils. For unamended soil, 55% of total P was mainly associated with Al (hydr)oxides. Organic residue application, regardless of residue quality, diminished the NH4F-extractable P (Al-P) fraction, but it had a nonsignificant effect on NaOH-extractable P (Fe-P). The majority of Al-P and Fe-P fractions were associated with crystalline Al and Fe (hydr)oxides. NH4Cl...