Soil Nitrate and Irate Dairies: Finding Sanity with Nutrient Management in New Mexico.

Nutrient management plans have been part of a collaborative training effort in New Mexico since 1998.  New Mexico NRCS, NMSU Cooperative Extension Service, and the NM Environment Department have trained 160 individuals representing private consultants, dairy operators, NRCS and Cooperative Extension personnel.   Despite this training the New Mexico Environment Department reports (personal communication) that more than 50% of the groundwater monitoring wells exceed the 10 mg/l nitrate-N standard set by the New Mexico Water Quality Control Commission.  This appears, at first glance, to be a failure of nutrient management plans.  However, locations that follow through with annual soil sampling, routine visits by crop consultants, and make informed decisions regarding crop rotations have been able to reduce residual soil nitrate that would otherwise be subject to leaching into groundwater resources.  Successful locations have used the NMSU Soil Test Interpretation Software to assist in estimating loading rates of effluent or solid manure. Residual soil nitrate-N levels above 100 mg/kg have been successfully reduced to less than 30 mg/kg by rotating out of corn/wheat rotations and into perennial crops such as alfalfa or bermudagrass.  Improved irrigation water management has also helped avoid nitrate-N losses due to leaching in some fields.  Overall, success is defined by New Mexico clientele as avoiding delays in permit renewal from the state environment department.  Successful nutrient management from an agronomic point of view is demonstrated by acceptable yields and lower fertilizer bills coupled with the beneficial use of residual soil nitrate to helps reduce its threat to groundwater contamination.