Assessment of Potassium Element on Lentil ( Lens culinaris Medic) Agronomy and Nutrient Use Efficiency in Calcareous Soils

Potassium (K) is considered as key element for plant growth and physiology and improvement of productivity and quality of crops. The potassium (K) reduction from agricultural soils of Indo-Gangetic plain had been observed due to rapidly increasing intensive cropping systems, in combination with imbalanced fertilization. Now, burning issue is needed to better understand the role and dynamic of K in plants and K-use efficiency of crops. Hence, this study was undertaken during two consecutive years of 2015-16 and 2016-17 to know the effects of different levels of potassium on lentil productivity, nodulation, nutrient uptake and K use efficiency. The experiment was laid out in randomized complete block design considering five treatments with thrice replicates. The treatments were T1 (K Control), T2 (15 kg K ha-1), T3 (30 kg K ha-1), T4 (45 kg K ha-1) and T5 (60 kg K ha-1) along with the blanket dose of N18P20S10Zn2B1.5 kg ha-1 and cowdung 3 t ha-1. Yield and yield attributes of lentil responded significantly to K fertilizer. The highest mean seed yield (1684 kg ha-1) and maximum seed yield increase over control (31.9%) got from T5 treatment followed by T4 treatment. The highest total nutrient (N, P, K, S, Zn and B) uptake, maximum nodulation and the highest protein content (29.4%) in seed was, however, recorded from the plot receiving of 60 kg K ha-1. Apparent K recovery efficiency was recorded higher (17.8%) from T4 treatment. Apparent K recovery efficiency followed the order: T4>T5>T3>T2. From the economic point of view, T5 followed by T4 treatment is viable and sound. The results of the experiment suggest that 60 kg K ha-1 might be applied along with N18P20S10Zn2B1.5 kg ha-1 for lentil cultivation in calcareous soils of Bangladesh. The K rates for fertilizer recommendation in lentil need to be revised to take account for highest yield by higher increasing rate of K in soil.