Pengaruh Kombinasi Pemberian Biochar dan Kotoran Sapi Terhadap Fase Vegetatif Tanaman Padi (Oryza sativa L.) dan Populasi Bakteri Penambat N-free

Abstract

Land degradation caused by declining soil organic matter and microbial activity has become one of the major constraints to rice productivity. Organic soil amendments, such as biochar and cattle manure, have the potential to improve soil quality while enhancing microbial activity involved in nutrient availability. This study aimed to evaluate the effects of combined biochar and cattle manure applications on the vegetative growth of rice (Oryza sativa L.) and the population of free-living nitrogen-fixing (N-free) bacteria. The experiment was conducted at the Greenhouse of Universitas Brawijaya and the Microbiology Laboratory of the Halal Center, Universitas Islam Malang, from December 2025 to June 2026 using a Randomized Complete Block Design with five treatments and four replications. The treatments consisted of a control, biochar at 30 t ha⁻¹, cattle manure at 40 t ha⁻¹, biochar at 30 t ha⁻¹ combined with cattle manure at 20 t ha⁻¹, and biochar at 15 t ha⁻¹ combined with cattle manure at 40 t ha⁻¹. Data were analyzed using analysis of variance followed by the Least Significant Difference test at the 5% significance level. The combined application of biochar and cattle manure significantly affected all vegetative growth parameters and the population of free-living nitrogen-fixing bacteria. The treatment of biochar at 15 t ha⁻¹ combined with cattle manure at 40 t ha⁻¹ produced the highest leaf number, leaf area, fresh biomass, dry biomass, and bacterial population, whereas the highest tiller number was obtained from the combination of biochar at 30 t ha⁻¹ and cattle manure at 20 t ha⁻¹. Although all plants developed chlorosis before entering the reproductive stage, the combined application of biochar and cattle manure improved soil biological quality and promoted vegetative growth. These findings indicate that the combined use of biochar and cattle manure has considerable potential as an organic soil amendment for sustainable soil fertility management, although further optimization of cultivation practices is required to support crop development through the reproductive stage.