Vegetation cover affects soil organic matter and activity of soil microorganisms. We investigated the intercropping effect of forage cactus with tree legumes on soil microbial biomass and organic matter in the semi-arid tropic, state of Pernambuco, Brazil. We assessed the following cropping systems: (i) Gliricidia sepium intercropped with cactus cv. IPA-Sertânia; (ii) Leucaena leucocephala intercropped with cactus cv. IPA-Sertânia; and (iii) Cactus cv. IPA-Sertânia in monoculture. Samples were collected during the dry and rainy seasons in the 0- to 0.10- and 0.10- to 0.20-m soil layers at 0, 1.5, 3.0, and 4.5 m in a perpendicular gradient from tree legume rows. The following responses were determined: δ13C and δ15N, C and N, microbial activity and biomass, and metabolic, microbial, and mineralization quotient. δ13C and δ15N varied with the distance from the trees. In the dry season and beginning of the rainy season, the cropping systems showed similar values for C, N, microbial activity, carbon, and nitrogen in the microbial biomass. The presence of tree legumes at the end of the rainy season favored soil microbiota, which showed a reduced loss of C-CO2, with no indication of metabolic stress and greater microbial biomass and microbial quotient in relation to forage cactus in monoculture.

Forage cactus responds positively to organic fertilization. However, little is known about the mineralization dynamics of the various sources of existing organic fertilizers. Thus, the objective was to evaluate the release of nutrients from different manure types and the nutrient accumulation in forage cactus across different cropping systems. Different manure sources (cattle, goat, sheep, and broiler litter) were evaluated for the following cropping systems: (i) Gliricidia sepium intercropped with cactus cv. IPA-Sertânia; (ii) Leucaena leucocephala intercropped with cactus cv. IPA-Sertânia; and (iii) Cactus cv. IPA-Sertânia in monoculture, in the tropical semiarid region of Brazil. The rate of decomposition and release of N, P, and K from manure was determined by incubating a litterbag, evaluated in different periods (0, 4, 8, 16, 32, 64, 128, and 256 days). Broiler litter released the greatest amount of N and P. Sheep manure released the greatest amounts of K. The greatest accumulations of N, P, and K in cactus biomass occurred when broiler litter was applied. Cactus monoculture accumulated less N over 256 days, indicating that the presence of tree legumes favors the accumulation of N in cactus. Broiler litter promoted the best synchronism between N release and N uptake in different cropping systems.

The use of agricultural practices such as fertilization and intercropping can improve the production of forage cacti. The objective of this study was to evaluate the agronomic characteristics of forage cactus intercropped with leguminous trees and fertilized with different sources of manure in the tropical semiarid region of Brazil. The research was carried out at the Agricultural and Livestock Research Enterprise of Pernambuco State during the period from March 2011 to September 2013. The following cultivation systems were used: (i) Gliricidia sepium (Jacq.) Kunth + forage cactus cv. IPA-Sertania [Opuntia cochenillifera (L.) Mill]; (ii) Leucaena leucocephala (Lam.) de Wit + forage cactus; and (iii) forage cactus in monoculture. All of these systems were fertilized with different sources of manure (cattle, goat, sheep, and broiler litter). The goat and sheep manure (16.6 and 16.5 Mg DM ha−1 year−1) provided the least production of cactus in the different cropping systems. Cattle manure provided greater production of forage and wood from legumes (1.4 and 4.3 Mg DM ha−1 year−1) and cactus (20.9 Mg DM ha−1 year−1). Gliricidia produced more forage and wood than Leucaena. Total production of the forage cactus-Gliricidia system produced 4.7 and 3.8 Mg DM ha−1 of biomass and wood in two years, respectively. The production and morphological characteristics of the cactus increased at further distance from the trees (3 m), and the opposite effect was observed for the concentrations of N, p, and K. Thus, cropping systems using forage cactus and tree legumes fertilized with manure represent an option for tropical semiarid regions.

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