Soil phosphorus dynamics as affected by Congo grass and P fertilizer

Abstract

Some plant species can change soil phosphorus (P) availability and this may be an important tool in managing tropical high fixing phosphorus soils. An experiment was conducted to evaluate phosphorus transformations in the soil and phosphatase activity during periods of Congo grass (Brachiaria ruziziensis, Germain et Evrard) growth in two tropical soils receiving 20, 40, 80, 160 mg dm −3 of inorganic P. Plants were grown for 84 days in 8-L pots. Acid phosphatase activity, P in the microbial mass, soil organic and inorganic P and P accumulation by Congo grass were evaluated. Phosphorus fertilization increased soil P availability, Congo grass yields and P accumulation in the plant. On average, less labile P forms in the soil were not changed by Congo grass; however, the P in the soil extracted with HCl (P-Ca -non labil form) decreased. This decrease may have resulted from the combination of the presence of grass and phosphatase capacity to dissolve less available P in the soil. Thus, soil exploration by Congo grass roots and the subsequent extraction of calcium phosphate may have increased the P concentration in the plant tissue. Despite the decrease in the P extracted from the soil with HCl resulting in increased labile P forms in the soil, the effect of Congo grass on the availability of P depends on the soil type.

Hydrolytic soil enzymes and their response to fertilization: a short review

“…Various studies have reported a negative effect of phosphorus fertilization on alkaline phosphatase (Kandeler et al, 1999;Sinsabaugh et al, 2008;Spohn & Kuzyakov, 2013) and acid phosphatase soil activity (Olander & Vitousek, 2000;Rosolem et al, 2014 (Marklein & Houlton, 2012).…”

Brachiaria as a Cover Crop to Improve Phosphorus Use Efficiency in a No-till Oxisol

“…The availability of P was lower in the presence of ruzi grass with both P sources in the first year (Table 1). However, Rosolem et al (2014) observed in a greenhouse experiment with more controlled conditions that ruzi grass can make soil P more available in the first cropping cycle. Moreover, higher accumulation of P in the plant tissue in the first year contrasted with a lower dry matter weight of ruzi grass compared to the second year (Table 3), and resulted in lower physiological efficiency of P in the 2010/2011 season, showing that weather conditions such as low rainfall and temperatures were possibly limiting the full potential for grass development.…”

“…They are important in nutrient recycling because of their high efficiency in taking up soil P through mechanisms such as development of large root system and lowering soil P fixation by exuding low weight organic acids like citrate, malate, and oxalate. They have specific, high affinity P carriers, and acid phosphatase activity is increased in the Brachiaria rhizosphere (Nanamori et al, 2004;Calonego and Rosolem, 2013;Janegitz et al, 2013;Rosolem et al, 2014).…”

Understanding Soil Phosphorus

“…No till or minimum tillage systems allow the accumulation of organic materials on the surface, which supply energy, carbon skeletons and electrons for growth and development of microorganisms [128] hence increase in biomass and eventually microbial P. Accumulated Po in the undisturbed rhizosphere may also result in high microbial activity; hence build-up of more stable Po fractions [165]. Additionally, minimal soil disturbance may promote increased populations of microorganisms and plant roots, thereby increasing synthesis and exudation of phosphatase enzymes and leading to enhanced transformation of Po into plant -available Pi [166].…”

“…The effect of tillage practices on soil P dynamics within the soil profile has been explained differently by different authors. Rosolem et al [166] attributed accumulation of P in the surface soil under zero-tillage to lack of physical disturbance that mixes fertilizer P thoroughly within the plough layer. On the other hand, Bolland and Brennan [168] argued that tillage practices which mix the topsoil increase availability through mixing the previously applied P, and thus improving the effectiveness of P fertilizer for subsequent crops.…”