Application bio-fertilizers to increase yields of zero-tillage soybean of two varieties under different planting distances in dry season on vertisol land of Central Lombok, Indonesia

Soybean crop is capable of establishing symbiosis with both Rhizobium bacteria and arbuscular mycorrhizal fungi (AMF) to form tripartite symbiosis. Symbiosis with Rhizobium bacteria enables a host plant to perform biological nitrogen fixation, while symbiosis with AMF enables host plants to increase nutrient uptake and water absorption so that they can be more tolerant to drought in dry seasons. This study aimed to examine the effect of application of Rhizobium and AMF bio-fertilizers on growth and yield of two soybean varieties under two treatments of plant spacing in vertisol ricefield during the dry season 2009 following rice crop without tillage. The experiment was arranged in a Randomized Block Design, with three blocks (replications) and three treatment factors, namely soybean varieties (V1= Anjasmoro; V2= Wilis), plant spacing (30x20 and 25x25 cm), and types of fertilizers (F1= without fertilizer; F2= Rhizobium application; F3= NPK only; F5= Rhizobium + AMF). Results indicated that application of both bio-fertilizers (Rhizobium and AMF) significantly increased soybean yield components, including grain yield, weight of 100 grains, grain number and total biomass per clump, compared with fertilization only with NPK or no fertilizers. There was no significant effect of plant spacing, but both varieties showed differences in plant height, grain yield, harvest index, and weight of 100 grains. However, there were interaction effects especially between variety and fertilization on plant dry weight, grain number and grain yield per clump, in which the highest grain yield was on soybean bio-fertilized with both Rhizobium and AMF, both in V1 and V2, but the average was higher in V1 (25.58 g/clump) than in V2 (15.03 g/clump). V1 was more responsive to dual application of the bio-fertilizers than V2.Soybean crop is capable of establishing symbiosis with both Rhizobium bacteria and arbuscular mycorrhizal fungi (AMF) to form tripartite symbiosis. Symbiosis with Rhizobium bacteria enables a host plant to perform biological nitrogen fixation, while symbiosis with AMF enables host plants to increase nutrient uptake and water absorption so that they can be more tolerant to drought in dry seasons. This study aimed to examine the effect of application of Rhizobium and AMF bio-fertilizers on growth and yield of two soybean varieties under two treatments of plant spacing in vertisol ricefield during the dry season 2009 following rice crop without tillage. The experiment was arranged in a Randomized Block Design, with three blocks (replications) and three treatment factors, namely soybean varieties (V1= Anjasmoro; V2= Wilis), plant spacing (30x20 and 25x25 cm), and types of fertilizers (F1= without fertilizer; F2= Rhizobium application; F3= NPK only; F5= Rhizobium + AMF). Results indicated that application of b...