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Title: Cover crops alter phosphorus soil fractions and organic matter accumulation in a Peruvian cacao agroforestry system

item HALL, HOLLIE - University Of Florida
item LI, YUNCONG - University Of Florida
item COMERFORD, NICHOLAS - University Of Florida
item GARDINI, ENRIQUE AR'VALO - Tropical Crop Institute (ICT)
item CERNADES, LUIS ZUNIGA - Tropical Crop Institute (ICT)
item Baligar, Virupax
item POPENOE, HUGH - University Of Florida

Submitted to: Agroforestry Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2010
Publication Date: 7/6/2010
Citation: Hall, H., Li, Y., Comerford, N., Gardini, E., Cernades, L., Baligar, V.C., Popenoe, H. 2010. Cover crops alter phosphorus soil fractions and organic matter accumulation in a Peruvian cacao agroforestry system. Agroforestry Systems. 80:447-455.

Interpretive Summary: Soils under long term cacao plantations are degraded due to intensive cultivation, non application of fertilizers and soil erosion. Leguminous cover crops due to their vegetative cover reduce soil loss by erosion, improve soil organic matter content and there by enhance soil quality. Research was under taken at Tarapoto Peru to determine the effects of leguminous cover crops on soil organic matter content and plant available phosphorous pool under cacao agroforestry system. Cover crops improved the soil organic matter content and phosphorous availability. Use of legume cover crops in cacao plantations could improve the soil fertility and reduce soil degradation. These findings are helpful to researchers, extension personnel and cacao farmers to improve the sustainability and production of cacao in highly degraded soils of the Andean region.

Technical Abstract: In many tropical soils, excessive weathering of primary minerals confounded by intense agricultural production has resulted in the depletion of organic matter and plant available forms of phosphorus (P). Long-term growth of cover crops in tropical agroforestry systems have been shown to influence nutrient cycling and soil organic matter pools. The objective of this experiment was to assess the effects of 2 years of cover-crop cultivation on organic matter accumulation and P bioavailability using Mehlich I and sequential fractionation methods. The experiment included six treatments in the understory of a cacao-plantain agroforestry system adjacent to lower mountain tropical forests of the San Martin district of Eastern Peru. Cacao and plantain formed the primary canopy on otherwise abandoned agricultural land. The treatments consisted of four perennial leguminous cover crops (Arachis pintoi,Calopogonium mucunoides, Canavalia ensiformis, and Centrosema macrocarpum), a non-legume cover crop (Callisia repens), and a control treatment (no cover crop). After only 2 years of cultivation, results suggest that all cover crop species accessed residual P pools in 0–5 cm soil depths as indicated by a decrease in the 0.5 M HCl extractable P pools when compared to control. Additional use of residual P pools by A. pintoi and C. macrocarpum were indicated by significant reduction in the 6.0 M HCl extractable P pool. Significant differences occurred between treatments. The C. ensiformis, C. mucunoides and C. repens treatments in 5–15 cm soil depths contained significantly more organic matter than the A. pintoi treatment. In 15–30 cm soil depths the C. ensiformis treatment contains significantly more organic matter than the A. pintoi treatment. Continued research should focus on monitoring the long-term effects of cover crop cultivation on the bioavailability of soil P pools in surface soil horizons, development of organic matter pools and the productivity of the cacao.