Comparison of soil quality and productivity at two sites differing in profile structure and topsoil properties

Abstract

Improved means for assessing the impact of management on soil quality (SQ) are needed. Objectives of this study were to assess SQ of two soils with similar taxonomy but dissimilar soil profile characteristics and compare SQ ratings with crop productivity. Soils evaluated included a glacial-till derived (GTD) loam/clay loam and an alluvial-derived (AD) sandy loam in central North Dakota, USA (403mm mean annual precipitation). Application of the Soil Management Assessment Framework (SMAF) to seven properties showed the soils had similar SQ index (SQI) values of 69 and 68 (out of 100 possible) for GTD and AD soils at 0–30cm depth, respectively, while they had SQI values of 89 and 87 at 0–5cm depth. The GTD soil had 17.1gkg−1 organic C compared to 9.8gkg−1 for AD soil, and higher SMAF scores for organic C and available water capacity (AWC), but lower scores for Olsen P and potentially mineralizable N. Soil productivity, as expressed by seed yield of dry pea (Pisum sativum L.), spring wheat (Triticum aestivum L.), and maize (Zea mays L.), was determined from two multi-crop sequence experiments conducted under no-tillage. Seed yields of spring wheat following spring wheat in 2003 and 2005 were 35% and 14% greater on GTD soil than on AD soil, but not different in 2003. Dry pea and maize forage yields were generally equivalent between soils, but 2004 maize seed yields on GTD soil following dry pea, spring wheat, and maize were 28%, 30%, and 54% lower, respectively, than on AD soil. Lower maize yields on GTD soil compared to AD soil during 2004 were associated with low subsoil hydraulic conductivity and shallower soil water depletion and root growth on GTD soil. Although GTD soil had higher levels of more stable SQ indicators (organic C, AWC) than AD soil, their similar, relatively high SQI values indicate positive responses to soil conservation management. Our results show the need for integration of soil profile and subsoil information with near-surface SQ assessments.