Effects of soil management practices on soil fertility measurements on Agave tequilana plantations in Western Central Mexico

Agaves have historically been an important crop in the Western Central Highlands of Mexico, used for food, livestock fodder and beverage production. The best known of these products, and one of the most financially significant, is the distilled spirit, Tequila. The success of agaves in this region has been attributed, in part, to unique environmental adaptations. Agaves used for production of the distilled spirit Tequila (Blue agave) have also been considered to have a minimal impact on soil fertility because they are harvested only every 6-10 years. In the past 20 years, with the rising global consumption of Tequila, cultivation of Blue agaves has grown more intense, prompting questions regarding the impact of commercial practices on soil quality. Researchers on related agave species have shown the potential for severe nutrient depletion and subsequent declines in yield in the absence of proper soil fertility management. This study examined the key physical and chemical indicators of soil fertility and how they were affected by tillage, the amendment of soils with distillery effluent, and the grazing of livestock. It was found that tillage decreased soil carbon levels along with nutrients associated with organic matter; mean levels of 2.44% C, 0.20% N and 10.99 mg P/kg soil were found on untitled sites compared with 1.29% C, 0.10% N and 3.53 mg P/kg soil for tilled sites. The addition of distillery effluent was found to increase soil cation levels (mean soil K, Mg, and Ca were 436.50, 364.40 and 1416.2 mg/kg on amended sites versus 299.50, 228.36 and 1013.5 mg/kg on non-amended sites) while livestock grazing had only a small effect on nutrient levels. The effects of tillage and livestock grazing need to be addressed by proper soil fertility management strategies need to be addressed to insure the long term health of soils in the region. (c) 2005 Elsevier B.V. All rights reserved.