Lime-fertilizer placement experiment on alfalfa

Many greenhouse and field experiments have been conducted to investigate the effects on yield and nutrient content of different crops when lime and/or fertilizer are mixed in the surface layer of acid, infertile soils. Nutrients can be absorbed by plant roots at deep soil levels if they are available and can result in a pronounced effect both upon the quantity and quality of the crop. Hence, information concerning the nature of the subsoil and the pattern of root distribution in it can add materially to our understanding of crop production. Root development and activity in the lower soil horizons has been investigated. Low crop production on soils with a hardpan or a tight subsoil is a common problem. The explanation frequently given for this low production centers around limited root development due to (a) the low fertility of the subsoil, (b) poor aeration, (c) the presence of a physical barrier preventing root penetration, or a combination of these factors. Many investigations on the possibility of increasing crop yields by deep plowing or by subsoiling have shown no improvement in yield over that obtained by conventional tillage. Some recent studies in humid regions, however, have shown some benefits derived from deep tillage when lime and fertilizer were incorporated to greater depths. For example, cotton and alfalfa have been studied in Tennessee (20), corn and oats in Iowa (12), corn in Illinois (9), and corn and sweet clover in Missouri (47). The use of lime, and large amounts of phosphate and potash fertilizers is essential for satisfactory forage production on many of the highly acid soils of the Southeastern United States. Lime is generally credited with a dual role in acid soils. Its direct function is to correct soil acidity and improve soil structure, and thus create an environment suitable to the growth and development of the roots. At the same time it performs several indirect functions. It stimulates microbiological activity in the soil, thereby increasing the availability of nitrogen, phosphorus, and sulfur to plants. It reduces phosphorus fixation by precipitating aluminum and manganese from the soil solution. In some soils at least, lime is responsible for enhancing the availability of potassium. Within the plant, lime performs several important functions. Calcium is essential for the growth of the meristems, especially in the development and functioning of the root tips. It is also believed that calcium is concerned with certain enzymes involved in respiration. The influence of lime on acid soils in promoting the growth, yield, and uptake of nutrients is of fundamental importance and immediate concern to agronomists. Therefore, experiments to investigate the effects of lime and/or fertilizer placement are very important in providing information on the wise use of these materials.