Soil Quality Management Under the Desert Southwest Farming System.

A long-term experiment was established in Artesia, NM to assess soil quality in a desert southwest soil under sprinkler irrigation, managed with organic and inorganic fertilizers. The treatments tested included a control plot with no fertilizer nitrogen input; synthetic nitrogen fertilizers and manure or compost applied at two rates to meet either the soil test recommended N rate or twice that rate. The experimental design was a randomized complete block replicated five times. The first applications of amendments were made to traditionally farmed with furrow irrigated row crops with tillage in 1997. All plots were converted to fescue pasture in 2003 and sprinkler irrigated. The plots are currently in the seventh year of production with the last treatment application made in 2009. Physical soil quality indicators assessed included available water capacity, dry aggregate size distribution, wet aggregate stability, field penetration resistance at 0-0.15m, 0.15-0.3m and 0.3-0.45m. Chemical measurements assessed included pH, electrical conductivity, nitrate-nitrogen at two depths (0-0.3 m and 0.3-0.6 m), extractable phosphorus and potassium. Biological indicators assessed were organic matter and active carbon. Results show that significant management effects were detected for several soil quality indicators. Indicators showing significant differences include wet aggregate stability, dry aggregate size distribution, organic matter and extractable soil phosphorus. Generally, manure/compost amended plots that received twice the recommended soil test plant available nitrogen, showed more favorable soil quality indicator values, while the control treatments with no fertilizer application gave the least favorable soil conditions. This work demonstrates the importance of the addition of organic sources of fertilizers in combination with no tillage for soil quality improvement in irrigated desert southwest soils.