Soil Health and Economic Potential of Organic, Reduced-till Cropping Systems in the Palouse.

Recent research suggests that organic, reduced-till (ORT) dryland cropping systems may have the potential to be economically viable and meet soil health and conservation needs in the hilly, highly erodible Palouse silt-loam soils of northern Idaho and eastern Washington. To investigate impacts on soil health, we measured chemical, physical and biological indicators in replicated plots allocated to two ORT cropping systems and one non-organic reduced-till system after five years of crop rotations. Earthworms were measured in winter wheat phases of organic and conventional wheat-pea rotations (Org-WP, Con-WP), and in four years of an organic alfalfa-wheat rotation (Org-Alf-5yr). Economic potential was assessed through cost of production analysis. Averaged across years, log transformed earthworm density was significantly greater (p<0.01) in Org-WP (109 individuals m^-2) than in Con-WP (51 individuals m^-2).  In Org-Alf-5yr, earthworm density did not change significantly during three years of perennial alfalfa, but increased significantly in the following winter wheat crop (187 individuals m^-2) (P<0.01). Fumigated extractable carbon as a measure of microbial biomass was marginally greater in Org-WP (100.3 µg g^-1) compared to Con-WP (76.9 µg g^-1) (p=0.06), and SOC was greater in Org-WP (28.6 Mg ha-1) than Con-WP (23.5 Mg ha^-1) in the top 10 cm of soil. Soil pH was greater in Org-WP (5.8) compared to Con-WP (5.5) (p<0.05) in the top 30 cm of soil and was similar between the two organic systems. Soil physical properties were not significantly different between cropping systems. The annual equivalent net present value (AENPV) of returns over total costs (RTC) is higher in Org-WP ($136 ac^-1) and Org-Alf-5yr ($42 ac^-1) assuming organic price premiums are available, compared to AENPV of RTC for a non-organic, wheat-spring pea rotation typical to this region ($31 ac^-1). Thus, development of small-scale ORT crop production has conceivable agronomic and economic value in Palouse agricultural systems.