Effects of long-term cultivation, grass reestablishment, and short-term cultivation on selected soil properties
Rolong-Cañas, Nelson A.
Improper soU management has resulted in the degradation of more than an estimated 6 million hectares of agricultural land in the Soudiem High Plains of Texas and New Mexico. The 1985 Food Security Act estabhshed the Conservation Reserve Program (CRP) whereby owners voluntarily bid highly erodible lands into the Program. Lands in the CRP are protected through accepted conservation practices for ten years. Assessment of the impact of mechanized agricidture and grass reestabhshment on soil properties is indispensable in order to understand soil response to seven decades of cidtivation and short-term effects of cultivation in reconverted CRP lands to agriculmre. The effects of long-term cultivated agriculture (approximately 70 years), conversion to native vegetation about 40 years ago, and reconversion to cultivated agriculture in 1985 in different plots were evaluated in the study. Changes in sod morphological, micromorphological, mineralogical, and selected physical and chemical properties were measured. The results indicated that the greatest differences occurred in the lower part of die plow layer (Ap2 horizons). The physical and chemical conditions of the Ap2 horizons were associated with the dominant type of grasses in the vegetated area, and the presence of an extremely dense Ap2 horizon in bodi die long-term and short-term cultivated fields. The influence of grass on sod properties was evident. Higher organic matter under grass significantiy improved the stabUity of aggregates and hence the properties dependent on soil structure. Conversely, the depletion of organic matter in the cultivated fields significantiy reduced the stability of aggregates and increased the susceptibility to wheel traffic compaction. The dense Ap2 horizon adversely affected the normal development of roots and restricted the transport of water.