Biofertilizers have been used as sources to improve plant nutrients in sustainable agriculture. Experiments were conducted to evaluate the potential of phosphate solubilizing bacteria (PSB) Bacillus megaterium var. phosphaticum and potassium solubilizing bacteria (KSB) Bacillus mucilaginosus inoculated in nutrient limited soil planted with pepper and cucumber. Results showed that rock P and K applied either singly or in combination did not significantly enhance soil availability of P and K, indicating their unsuitability for direct application. PSB was a more potent P-solubilizer than KSB, and co-inoculation of PSB and KSB resulted in consistently higher P and K availability than in the control without bacterial inoculum and without rock material fertilizer. Integrated rock P with inoculation of PSB increased the availability of P and K in soil, the uptake of N, P and K by shoot and root, and the growth of pepper and cucumber. Similar but less pronounced results were obtained when rock K and KSB were added concomitantly. Combined together, rock materials and both bacterial strains consistently increased further mineral availability, uptake and plant growth of pepper and cucumber, suggesting its potential use as fertilizer.

An excess of salinity and boron (B) can limit production of hot pepper (Capsicum annuum L.), but little is known about the physiological responses, including antioxidant activities, in response to these excesses. We investigated the physiological responses and defense mechanisms of hot pepper grown under salinity (NaCl) stress at 3 and 6 dS/mand B stress at 15 and 30 mg/kg. Dry weight and the total chlorophyll content decreased with increasing salinity and B levels. The toxic effect of B was greater under saline conditions. Higher levels of salinity and B resulted in increased B concentrations in leaves. The stomatal resistance values increased as the combined levels of salinity and B increased. Furthermore, increasing salinity, B or both increased activities of H 2 O 2 , SOD, POX, APX and GR, which increased oxidative stress, compared to the control plants. Increases in combined salinity and B levels disrupted plant nutrient balance and water use, and induced production of secondary toxic substances leading to an increased plant tissue concentration of H 2 O 2 , and suppression of growth in hot pepper.