Liming of alfalfa in a greenhouse study

The use of agricultural lime has been recognized down through the ages as a practice that is basic to good soil management in humid regions. The effects of liming are a complex of many contributing physical, chemical. microbiological and physiological factors. Its direct function is to correct soil acidity, improve soil structure and create an environment suitable to the growth and development of plants. Liming enhances the availability and plant uptake of elements such as nitrogen, phosphorus, molybdenum, calcium, and magnesium. At the same time it drastically reduces the concentration of iron, aluminum and manganese, which under very acid conditions are apt to be present in toxic quantities. In at least some soils, it enhances the availability of potassium. Lime stimulates the general-purpose. heterotrophic soil organisms, thereby increasing their activity on organic matter and the releasing of nitrogen. This favors the formation of humus and also encourages the elimination of certain intermediate products that might be toxic to higher plants. Within the plant, too, lime performs many functions. Calcium is essential for the growth of the meristems. the development and functioning of root tips, and for certain enzymatic reactions involved in respiration. The uptake of nutrients by roots of plants from the soil medium is a complex physiological process, the rate of which is greatly influenced by environmental factors. Greenhouse experiments have several advantages in this regard, most important of which is the control of numerous environmental factors. It is also possible under greenhouse conditions to design experiments to include a large number of treatments and a variety of soils; they can be carried out at any time of the year Irrespective of the season. Furthermore, Investigations of a fundamental nature such as soil-plant relationships, can be made in a greenhouse without the involvement of elaborate field studies, high cost and undue labor. At the same time, they can serve as pilot projects for appropriate field studies in the future. The influence of lime on acid soils in promoting the growth, yield and uptake of nutrients is one of fundamental importance and immediate concern to the agronomist. Lime-fertilizer experiments in the greenhouse involving the use of calcium, phosphorus and potassium on acid infertile soils are therefore very important in giving some indication as to the wise use of these nutrients. Since root development of crops in acid soils is very much dependent on the soil condition, its lime content and the nature of its zone of penetration, the placement of lime as an additional factor in the balance of fertilization assumes relatively great importance. This work was undertaken with the following objectives in view: 1. To study the influence of liming and fertilization of an acid soil on growth, yield, root development and uptake of various cations by plants. 2. To study the influence of placement of lime in different layers of the soil on the above factors. Hartsells loam was the soil used for the study. It was low in all nutrients. Alfalfa was used as the indicator plant because it is known to be sensitive to soil acidity