Agronomic Impact and Cost Analysis of Natural Rocks and Biological Inoculants in Potato Production

Potato ( Solanum tuberosum ) is an important food crop. However, intensive cultivation has led to increased reliance on chemical fertilizers, raising environmental and economic concerns. One of the concerns in potato plantations is phosphorus, which often exhibits low availability due to leaching and poor use efficiency, coupled with rising fertilizer production costs. This study investigates the agronomic and economic impacts of using natural rock amendments combined with plant growth-promoting rhizobacteria (PGPR) as sustainable alternatives to chemical fertilizers on the yield and tuber quality of potato. A field experiment assessed three treatments: conventional chemical fertilizers (T1), reduced chemical fertilizers combined with PGPR ( Bacillus megaterium , Bacillus mucilaginosus , and Azotobacter ) (T2), and natural rock amendments of potassium feldspar and rock phosphate combined with PGPR (T3). Results showed that T2 and T3 demonstrated improved tuber quality compared to T1, with T3 achieving the highest starch content (314.05 mg/g FW) and reduced sugar content (102.03 mg/g FW). Furthermore, T3 improved soil quality after the growing season, showing higher phosphorus and potassium availability compared to T1. Economically, T3 reduced operating costs by 11% and achieved the highest yield (42 tons/ha). The return on investment for T3 reached approximately 79.48% (USD 3988/ha), with a 40.9% profit increase compared to T1 (USD 2460/ha) These findings confirm that integrating PGPR with natural rock fertilizers offers a cost-effective and durable alternative to conventional fertilization practices, enhancing productivity and profitability while providing significant opportunities for achieving the Sustainable Development Goals and promoting long-term soil sustainability.