Purple nonsulfur bacteria affect nutrient uptake, growth, and yield of hybrid maize by solubilizing potassium in dyked alluvial soil

<h2>Abstract</h2> Although potassium (K) solubilizing microbes have been widely investigated, a candidate that can adapt to a wide range of environments is needed in the era of climate change. Among them, purple nonsulfur bacteria (PNSB) are suggested. Therefore, the study was conducted to evaluate the effectiveness of K-solubilizing PNSB (K-PNSB) on soil chemistry, plant growth, yield, and K uptake of hybrid maize grown in alluvial soil in An Phu district, An Giang province, Vietnam under a nethouse condition. The experiment was designed with factor A as K fertilization rates (0 %, 25 %, 50 %, 75 %, and 100 %) and factor B as K-PNSB (the negative control, <i>Cereibacter sphaeroides</i> M-Sl-09, <i>Rhodopseudomonas thermotolerans</i> M-So-11, <i>Rhodospeudomonas palustris</i> M-So-14, and a mixed use of M-Sl-09, M-So-11, and M-So-14). The results indicated that fertilizing with K increased maize grain yield by 2.50–6.19 % compared to the control, with the optimum yield achieved at a 75 % K fertilization rate. The application of K-PNSB improved plant growth, including plant height by 7.83–9.37 %, number of green leaves by 23.7–35.1 %, leaf length by 2.77–4.30 %, and ear forming height by 11.3–15.7 %; and yield traits, including ear length by 4.22–5.42 %, number of grains per row by 5.11–9.12 %, and grain yield by 3.51–8.33 %. Additionally, the application of K-PNSB also led to an increase in pH_H2O by 2.59–5.79 %, NH₄⁺ by 19.4–52.8 %, soluble P by 11.0–18.7 %, and exchangeable K by 13.0–34.0 %, total K uptake by 15.8–30.0 %, and a decrease in EC by 12.8–18.0 % and Ca-P by 3.92–10.9 %. The mixed use of the three K-PNSB strains was as effective as using 100 % K fertilizer according to local recommendations. These results demonstrate that the three selected K-PNSB strains effectively provide nutrients for plants.