ABSTRACT A field experiment was conducted at Gopalpur, Natore during November 2020 to March 2021 with the objectives to evaluate the effects of combined application of organic fertilizer and rhizobium bio-fertilizer to reduce N-fertilizer use in terms of growth and yield maximization of lentil. The experiment used lentil Binamasoor-8 laid out in a randomized complete block design (RCBD) having six treatments with three replications. Unit plot size was 2mx3m (6 m2), row to row and plant to plant distances were 40 cm and        10 cm, respectively. Six treatments were T1 = N + P, K, S, Zn and B, T2= Bio-fertilizer + P, K, S, Zn and B, T3 = Organic fertilizer + P, K, S, Zn and B, T4= Organic fertilizer + Bio-fertilizer + P, K, S, Zn and B, T5 = N + P, K, S, Zn and B + Organic fertilizer+ Bio-fertilizer and T6= Control. All the fertilizers were applied as per recommendation. The used sources of N, P, K, S, Zn and B were urea, TSP, MOP, gypsum, zinc sulphate and boric acid, respectively. Data on growth and nodulation were recovered at 50 % flowering stage. Yield attributes were recovered after ripening. The results of the experiment revealed that the integrated use of Organic and Bio-fertilizer (T4) ensured the better performances in respect of plant height, number of branches, number of nodule, number of pod per plant, and number of seeds per pod, 100-seed weight, and grain yield of lentil.

Key words: Rhizobium, organic fertilizer, lentil, growth, yield.

Introduction Bangladesh is an agro-based nation where numerous crops are developed. Among them, pulses constitute the main sources of plant protein for people, especially the poor people of Bangladesh, particularly the destitute individuals of Bangladesh. Lentil (Lens culinaris Medik) is an important grain legume crop in Asia. It’s the second most important pulse crop of Bangladesh in terms of area (2.704 Lac hectares) and production (3.555 Lac metric ton) (BBS, 2016) and it ranks the highest in terms of consumer preference as total pulse consumption (Krishi Diary, 2018). Lentils productivity is below potential due to low input use and limited use of modern agronomic practices.

Declining soil fertility is a major obstacle to crop production. For the solution of above concern, the management of soil fertility, soil health and environmental threat through INM system is the key for the development of sustainable agriculture. Nutrition is essential for proper growth and high grain yields of lentil. Organic and Bio fertilizer can help to improve most of the physical, biological and chemical properties of the soil, thereby improving soil fertility (Vishnoi et al., 2013). Possible interventions in agriculture include the combined use of organic and bio-fertilizers as well as bio-stimulants in order to increased balanced nutrient supply (Wani et al., 2016). However, integrated nutrient management (INM) is an approach that seeks both increase in agricultural production and safeguard the environment for future generations by integrated using of organic and bio-fertilizers, crop residues, and other living materials in such a balance that enhances fertilizer use efficiency, thus resulting in increased crop yields while indirectly minimizing the environmental risks in the World.