Response of integrated use of humic acid and chemical fertilizer on growth and yield of rice crop (ORYZA SATIVA L.) in calcareous soil

Poor soil organic carbon and low fertility are interrelated problems that can significantly negatively impact agricultural productivity and ecosystem health. Organic carbon is crucial to soil fertility as it supports soil structure, water retention, and nutrient availability. That's why scientists suggest using organic fertilizers to overcome this issue. Humic acid (HA) is one of such organic amendment that plays a critical role in soil health and fertility. Although a lot of work has been done so far on HA, the novelty of current study was the utilization of K and GA3-enriched humic acid. For experimental purposes, 3 levels of fertilizers (i.e., control, 50% and 100% recommended NPK) were applied with and without HA in rice. There were 3 replicates following the randomized complete block design (RCBD). Results showed that the 50% RDF application rate resulted in a 140.7% increase in plant height, while a 100% RDF application rate led to a 184.2% increase. Specifically, a 50% RDF application rate resulted in a 8.8% increase in spike length, while a 100% RDF application rate led to a 23.4% increase. The use of 50% RDF with humic acid resulted in a significant increase of 41.4%, while the application of 100% RDF with humic acid led to a 40.1% increase compared to the control treatment in 1000 grains weight. In conclusion, the combined use of humic acid and 50% RDF could prove a better strategy to obtain optimum yield in rice crop in calcareous soil than 100% RDF. However, 100% RDF can maximize plant height and spike length. More investigations are recommended at the field level to introduce GA3 and K-enriched HA as effective amendments to improve rice growth under limited fertilizer supply in poor, fertilized calcareous soils. (author)