Productivity and Nutritive Value of No-Input Minimum Tillage Organic Forage Systems

Strong interest in organic produce has warranted great demand in organically produced forages. However, extremely limited research has focused on organic forage production and its ecological contribution. Grass-legume biculture has been suggested to reduce dependency on external N inputs, control weed encroachment, and achieve better soil health. A 2-year study was designed as a conservative organic system with minimum tillage and no external inputs to investigate productivity, botanical composition, nutritive value, mineral concentration, economic benefit, and soil total carbon changes in five certified forage biculture systems; including (1) one annual rotation of winter wheat-Austrian winter pea biculture followed by sorghum-sudangrass hybrid-cowpea biculture, and four perennial systems of (2) bermudagrass-alfalfa, (3) tall fescue-white clover, (4) old world bluestem-sainfoin, and (5) orchardgrass-alfalfa bicultures. Annual systems indicated the greatest productivity (12.7 Mg ha(-1)) followed by old world bluestem-sainfoin (11.3 Mg ha(-1)) and bermudagrass-alfalfa (10.3 Mg ha(-1)) bicultures; but with very limited nutritive value advantages, low mineral concentration, and poor economic return. Perennial systems, particularly old world bluestems-sainfoin biculture, indicated great adaptation, soil carbon enhancement capacity. Monthly biomass production was influential on several nutritive value indices (P < 0.05, R-2 approximate to 0.5) within many forage systems. No treatment effects were detected on soil total carbon (P = 0.27), but significant year-wise increase was found under old world bluestems-sainfoin biculture (P < 0.05). Soil moisture levels were affected by treatments and correlated well to botanical composition. Path analysis indicated that Radiation Use Efficiency is the key driver for determining forage yield in the temperate environment.