Vol. 11, Núm. 2 (2013)

Abstract

Organic agriculture is growing rapidly in New Mexico, USA and world-wide primarily due to the concerns
related to soil and environmental problems associated with conventional farming system. The organic
system relies on manure and the salts associated with the feed and manure carries a risk of soil
salinization. The objective of this study was to determine the salinity and sodicity levels of furrow or flood
irrigated soil under several years of organic farming system. In 2009, three organic farms selected were
under organic agriculture for last seven (OF7), ten (OF10) and thirteen (OF13) years since certification. A
conventional farm was also selected as a control. The estimated nitrogen content in soils of organic farms
showed a surplus; however, care must be taken to account properly for soil nitrogen losses due to leaching,
immobilization and other complex processes related to nitrogen transformation in soil. The soil salinity
(1:1 soil to water extract method) determined during 2009 ranged from 0.67 to 1.04 dS/m under OF7,
from 0.65 to 0.80 dS/m under OF10, and from 1.09 to 1.41 dS/m under OF13, indicating slightly saline
conditions under the oldest organic farm below the 4 dS/m threshold for soil salinity for crops grown in
experimental farms. Similarly, sodium adsorption ratio (SAR) showed an increasing trend from OF7 (4.9)
to OF13 (8.8), but was below the threshold of 15 for most agricultural crops. There is a need to continuously
monitor the soil fertility, salinity and sodicity in the organic fields.