The Influence of Excessive Liming on Boron Deficiency in Soils

Greenhouse liming investigations begun in 1923 at the Alabama Agricultural Experiment Station showed negative results from liming on many of the soils of the Coastal Plains; such results are now referred to as over-liming injury (1, 3). Over-liming on these soils was not overcome with moderate amounts of fertilizers containing nitrogen, phosphorus, and potassium, nor were the additions of magnesium, calcium silicate, manganese, or iron of any value in preventing the injury caused by over-liming. The injury was associated with pH values above 6.8 and with soils of low base exchange capacities. The problem of over-liming remained unsolved until recently when a study on a Norfolk sandy loam was reported which showed that boron deficiency was the causative agent (g). Since the above studies on overliming were conducted on the relatively light-textured soils of the Coastal Plains, it seemed important to determine whether similar results would be obtained on widely different soils in texture and origin. Accordingly, twenty soils representing fifteen soil series were obtained for conducting greenhouse pot experiments. These experiments were made using none, moderate, and excessive amounts of C. P. CaC03 both with and without boron amendments to the soils. Observations made on growth and yield curves of several successive crops from these pot cultures served to indicate when over-liming and boron deficiency occurred. Soluble boron and pH determinations were made on the soil cultures at different intervals for use in interpreting the growth response to the lime and boron applications. Results of plant growth in the pot cultures showed that excessive lime brought about over-liming injury on fifteen of the twenty soils under investigation. The injured plants showed evidence of boron deficiency which was partially or completely overcome in the pot cultures treated with boron (See Figure 1). Over-liming was independent of soil texture but was related to the acidity and the degree of leaching to which the soils had been naturally subjected. Undoubtedly, the chemical composition of the soil is important since over-liming did not occur on Cecil clay which contains tourmaline, a boro-silicate mineral. In some of the soils not over-limed, there was some increase in yield from the application of boron. Typical examples of yields of four successive crops on several soils are given in Table 1.