Can Crop Productivity Benefit From Cover Crops and Organic Additions in an Irrigated Environment?.

Nationwide interest in improving soil quality has led many federal and state institutions in the semi-arid southwest to explore the feasibility of improving soil quality through the adoption of cover cropping, rotations, and the addition of compost or manures. Whether or not this can successfully be done in an irrigated environment of the semi-arid southwest is the long-term goal of an ongoing study in southeastern New Mexico, USA.  Soils were amended in 1998 with either synthetic fertilizers or manures to supply 1X or 2X the estimated nitrogen need of different cash crops. An untreated control was included in a randomized complete block design with five replicates.  Crops have included cotton, corn, chile, fescue pasture grass, and pinto beans.  Crop productivity and soil fertility parameters will be presented along with soil organic matter content, a measure active carbon, available water holding capacity, and percent aggregation. Soils treated with manure or compost over time improved soil aggregation over that of the control. Manure and compost applied at 2X rate improved the percent soil aggregation, active carbon, and organic matter over that applied at the 1X rate and had greater levels than traditional fertilization.  The application of manure and composts also improved soil-test P, K, Zn, Mn, and B levels over that of the synthetic sources but varied by rate of application.  Relative productivity will be compared among the treatments to assess agronomic benefits to the standards of farming in an irrigated environment.