title: Decomposition, nitrogen and carbon mineralization from food and cover crop residues in the central plateau of Haiti.
abstract: Cover crops are a major focus of conservation agriculture efforts because they can provide soil cover and increase nutrient availability after their mineralization in cropping systems. To evaluate the effect of residue type and placement on rate of decomposition and carbon (C) and nitrogen (N) mineralization, residues from two food crops, maize (Zea mays L.) and common bean (Phaseolus vulgaris L.), and two promising cover crops, sunn hemp (Crotalaria juncea L.) and sorghum sudangrass (Sorghum bicolor [L.] Moench x S. bicolor var. Sudanese [Piper] Stapf) were used in a litterbag study in the Central Plateau region of Haiti from May to September, 2013. Residues were placed in litterbags at a rate equivalent to 3.25 Mg residue ha(-1) either on the soil surface or buried at 15 cm to represent a tilled and no-tillage system, respectively. Initial C:N ratios were: maize > common bean > sorghum sudangrass > sunn hemp. Highest residue mass loss rates and C and N mineralization generally occurred in the reverse order. Overall, surface-placed residues decomposed more slowly with 40 and 17 % of initial residue mass of surface and buried residues, respectively, remaining at 112 days. Carbon and N mineralization was higher when residues were buried. Net N mineralization of buried residues was 0.12, 0.07, 0.06, and 0.03 g N g residue(-1) for sunn hemp, sorghum sudangrass, maize, and common bean, respectively over 112 days. To achieve the goal of increasing nutrient supply while maintaining year-round cover, a combination of grass and legume cover crops may be required with benefits increasing over multiple seasons.
authors.affiliation: Department of Crop and Soil Environmental Science, Virginia Tech, Blacksburg, VA 24061 USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Lynch
authors.affiliation: West Florida Research and Education Center, University of Florida, Jay, FL 32565 USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Mulvaney
authors.affiliation: Department of Crop and Soil Environmental Science, Virginia Tech, Blacksburg, VA 24061 USA.
authors.forename: S C
authors.initials: SC
authors.lastname: Hodges
authors.affiliation: Department of Crop and Soil Environmental Science, Virginia Tech, Blacksburg, VA 24061 USA.
authors.forename: T L
authors.initials: TL
authors.lastname: Thompson
authors.affiliation: Department of Crop and Soil Environmental Science, Virginia Tech, Blacksburg, VA 24061 USA.
authors.forename: W E
authors.initials: WE
authors.lastname: Thomason
keywords: Conservation agriculture; Cover crop; Haiti; No tillage; Nutrient cycling