Sustainable Enhancement of Sugar Beet Productivity in Salt-Affected Soils Using Humic Substances and Bacillus biofertilizers

The current study evaluates the efficiency of using humic-substances and biofertilizers, individually or in combinations, to boost sugar-beet growth and productivity in a saline-sodic soil (EC=9.7-11.3 dS m-1-ESP>15) while improving soil properties. To attain this aim, a two-season field-experiment was conducted in a complete-randomized-block-design, comprising 7-treatments: the recommended doses of (NH4)2SO4+CaH2PO4 (reference, T1), (NH4)2SO4+H3PO4(T2), bio-N&P-biofertilizers+ rock-phosphate(T3), bio-N&P-biofertilizers+ rock-phosphate+ HK (T4), bio-N&P-biofertilizers+ rock-phosphate+HA(T5), bio-N&P-biofertilizers+ rock-phosphate+FA (T6), N-fixer+H3PO4(T7). Results revealed that stressed-plants exhibited high proline-levels in shoots, especially in treatments from T3 to T6. This rise in proline was strongly correlated with tuber yield quantity and quality, while also contributing to significant reductions in soil EC and ESP. Additionally, proline-level was correlated positively with each of available-P-content in soil, and the corresponding P-concentrations in plant tissues. Probably, stressed-plants augmented activities of soil-bacteria within their microhabitat that dissolved-P; while intensifying more carriers to take up soil-P. Likewise, K-content rose significantly in treatments T3 to T7. Substituting CaH2PO4 with H3PO4 in T2 recorded the highest tuber-yield, which was statistically comparable to the ones achieved by T4 and T6. Concerning EC, it significantly declined across all treatments, including T1; though all soils remained saline. Similarly, soils turned into non-sodic by the end of the 2nd season. Soil additives likely enhanced nutrient uptake by promoting low-affinity K carriers, which hardly distinguish between K and Na, thereby reducing ESP. These findings confirm that sugar beet can help reclaim highly saline soils when supplemented with biofertilizers and humic-substances; nevertheless, extended periods are needed to attain optimum results.