Lime and foliar application of molybdenum affects nodulation, nutrient uptake and pod production in soybean grown in acid soils

Soil acidity is commonly ameliorated with lime while little attention is given to the application of molybdenum which is deficient in acid soils. Molybdenum is an important component of the nitrogenase enzyme essential for the symbiotic nitrogen fixing bacteria.  An experiment was conducted in a controlled environment at the University of KwaZulu-Natal to evaluate the effect of lime and molybdenum on nodulation, growth and shoot nutrient content of soybean. The experiment was a randomised complete block design with three rates of lime applied at 0, 2650 and 4280 kg ha-1 and molybdenum as ammonium molybdate at 0 and 0.5 g L-1. Lime significantly (p<0.01) increased the uptake of Ca and P but decreased that of Mn. Also, increasing lime levels positively influenced most of the important plant growth parameters measured in the study. Molybdenum application significantly increased nodule formation but did not influence the concentration and uptake of the nutrients measured. Lime application also improved soil Ca and Mg but reduced Mn and exchangeable acidity levels at the end of the study.  The treatment combination of lime at 4280 kg ha-1 and ammonium molybdate at 0.5 g L-1 gave the best result in nearly all parameters tested and it can hence be concluded that this combination improves both the nutrient uptake and nodulation of soybean grown in soil with very high acid saturation.