Abstract
In sustainable agriculture, seeking eco-friendly methods to promote plant growth and improve crop productivity is a priority. Humic acid (HA) and plant growth promoting rhizobacteria (PGPR) are among the most effective methods that utilize natural biologically-active substances. The aim of the present study was to analyze the effect of the presence of HA on potato (Solanum tuberosum L.) inoculation with PGPR (Bacillus megatorium and Bacillus subtilis) when compared to control and recommended doses of NPK. Seed tubers treated by humic acid (200, 400, and 600 kg ha−1) and PGPR, separately or in combination, and NPK (50% and 100%) were planted into soil and untreated soil. Treatments were assessed for plant growth, classified tuber yields, quality, and mineral contents of potato tubers. There were highly significant increases in potato growth, tuber yields, and quality in PGPR and HA inoculated crops. Tuber size, weight, specific gravity, dry matter, starch, protein, and mineral contents (except Cu) were improved with PGPR treatments and further increased when administered with humic acids. Inoculation with PGPR mixed culture and 400 kg ha−1 HA increased total potato tuber yield by about 140% while conventional single treatment of 100% NPK fertilizer only led to an increase in potato production of 111% when compared to the control. The results demonstrated that this integrated approach has the potential to accelerate the transformation from conventional to sustainable potato production.
Highlights
The intensive input agricultural systems that ensure high yield and quality are one of the most disruptive practices for the planet’s resources, but are justified by economic requirements, and the need to feed a growing population
Significant increases were observed in potato growth, tuber yields, and quality after inoculation with both plant growth promoting rhizobacteria (PGPR) (Bacillus strains) and PGPR mixed culture (Bacillus megatorium M3 and Bacillus subtilis OSU-142), and further improved after combined application with humic acid
These two strains in Bacillus genus are known for their effects that supported by the capacities to produce indole-3-acetic acid (IAA) and 1–aminocyclopropane–1-carboxylate (ACC) deaminase, to fix nitrogen or to solubilize phosphorus, and their biocontrol capacity against a wide range of bacterial and fungal pathogens that lead to significant economic losses in agricultural crops [26,27,28]
Summary
The intensive input agricultural systems that ensure high yield and quality are one of the most disruptive practices for the planet’s resources, but are justified by economic requirements, and the need to feed a growing population. Excessive use of non-renewable chemical fertilizers and pesticides risks agricultural sustainability through the deterioration of soil and water resources, environmental quality and health. Current trends in agriculture are focused on improving the efficiency of fertilizer use and reflect a revived an interest in transition from conventional to organic farming for basic vegetables consumed for human nutrition. Potatoes are widely cultivated in more than 164 countries and consumed in fresh or processed form almost daily by more than a billion people. Organic production of this crop for human consumption promotes human health and enhances nutritional safety. The development of a vibrant, profitable, and sustainable organic potato sub-industry in potato growing countries depends mainly on improved nutrient management through organic matter mineralization and biological control of diseases and pests
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