Soil Fertility and Crop Responses at Selected Landscape Positions

A large part of the glacial drift plain of North Dakota is composed of sloping surfaces which are the result of late Wisconsin glaciation and post glacial erosion and sedimentation. The geologic processes of erosion and sedimentation affect soils, their properties, and crop response at various landscape positions. There is limited research data on the effect of landscape position on soilfertility levels and crop production. Knowledge of these relationships on a hillslope can aid in understanding crop growth at various landscape positions. The objectives of this research were to gain an understanding and insight into the occurrence and distribution of soils and their properties as they exist on the landscape in relation to crop responses. Soil properties measured with respect to landscape position were soluble salt content, inorganic C content, water table levels, and soil test levels of N, P, and K. The crop responses measured were emergence plant counts, plant height, maturity, and crop yield. Soil NO₃-N and extractable P levels were minimal at the shoulder position, where erosion activity was greatest and maximal at the toeslope where sedimentation and higher soil moisture contents were found. Minimum exchangeable K levels were found at the salt rim where electrical conductivity values were high. Initial plant populations were lowest at the salt rim located at the footslope position. Plant height was greatest at the backslope and least at the footslope. Lowest yields and highest grain moisture contents were found at the lowest landscape positions. Highest yields occurred at the backslope while lowest grain moisture contents were found at the shoulder position. Results of this study show that differences in plant responses to landscape position exist primarily because of changes in soils and their associated properties. Landscape position is helpful in identifying soil types which can aid in fertilizer management decisions.