Upendra M. Sainju1, Brett L. Allen1, TheCan Caesar-TonThat1 and Andrew W. Lenssen2, (1)USDA-ARS, Sidney, MT (2)Agronomy, Iowa State University, Ames, IA
Information on the effect of long-term management on soil nutrients and chemical properties is scanty. We examined the 30-yr effect of tillage frequency and cropping sequence combination on dryland soil Olsen-P, K, Ca, Mg, Na, SO4-S, and Zn concentrations, pH, electrical conductivity (EC), and cation exchange capacity (CEC) at the 0-120 cm depth and annualized crop yield in the northern Great Plains. Treatments were no-till continuous spring wheat (Triticum aestivum L.) (NTCW), spring till continuous spring wheat (STCW), fall and spring till continuous spring wheat (FSTCW), fall and spring till spring wheat-barley (Hordeum vulgare L., 1984-1999) followed by spring wheat-pea (Pisum sativum L., 2000-2013) (FSTW-B/P), and spring till spring wheat-fallow (STW-F, traditional system). At 0-7.5 cm, P, K, Zn, Na, and CEC were 23 to 60% were greater, but pH, buffer pH, and Ca were 6 to 31% lower in FSTCW, FSTW-B/P, and STCW than STW-F. At 7.5-15 cm, K was 23 to 52 % greater, but pH, buffer pH, and Mg were 3 to 21% lower in FSTCW, FSTW-B/P, and STCW than STW-F. At 60-120 cm, soil chemical properties varied with treatments. Annualized crop yield was 23 to 30% lower in STW-F than the other treatments. Continuous N fertilization probably reduced soil pH, Ca, and Mg, but greater crop residue returned to the soil increased P, K, Na, Zn, and CEC in NTCW and STCW compared to STW-F. Reduced tillage with continuous cropping may be adopted for maintaining long-term soil fertility and crop yields compared with the traditional system.