Phosphate-Solubilizing Bacteria as a Panacea to Alleviate Stress Effects of High Soil CaCO3 Content in Phaseolus vulgaris with Special Reference to P-Releasing Enzymes

The present study examines the role of leguminous compost (LC), humic acids (HA), and phosphate-solubilizing bacteria (P-SB) in alleviating the stress effects of high soil CaCO3 content in Phaseolus vulgaris. Two pot trials for two consecutive seasons; fall 2019 and summer 2020 were implemented in an open greenhouse. A mixed three-way ANOVA, two independent factors (season and soil treatments) and one within factors (time) were used with four replicates. Residual maximum likelihood (REML) analysis was used for the mixed model of the studied traits. Inoculation of calcareous soil with P-SB (a 1:1 mixture of two Pseudomonas sp.; Ps. mallei and Ps. cepaceae) significantly exceeded LC, HA, or even LC+HA for the positive results obtained. P-SB facilitated nutrient solubility (e.g., N, K, Fe, and Mn), including conversion of insoluble phosphorous into a form available in the tested soil due to increased soil enzymatic activities (e.g., phosphatases and phytases). This mechanism, combined with a decrease in soil calcium carbonate content and an increase in cation exchange capacity (CEC) and organic matter (OM) content, increased the availability of various nutrients to plants, including P, in the soil, which contributed to the increased plant output. Adequate P content in plants led to a marked decrease in plant acid phosphatase activity under high content of CaCO3. The study concluded that the use of P-SB promotes biological activities, nutrient availability, and thus the productivity of calcareous soils, enabling Phaseolus vulgaris plants to withstand stress produced by high CaCO3 content through the development and/or adoption of potentially effective mechanisms. Strong highly significant interactions between the treatments and time were observed using the Wald’s statistics test, which indicates a positive correlation.

Lime requirement of acidic Queensland soils.II. Comparison of laboratory methods for predicting lime requirement

A number of laboratory procedures for predicting lime requirement were evaluated by using 40 acidic surface soils from eastern Queensland. The methods were compared on the basis of their ability to predict the lime requirement to pHw values of 5.5 and 6.5 obtained from soil-CaCO3-moist incubations. The laboratory methods evaluated included 1M KC1 extractable Al, equilibration of soil : water suspensions with varying amounts of added Ca(OH)2, the Shoemaker, McLean and Pratt (SMP) single-buffer method, the SMP double-buffer method, the Yuan double-buffer method and the Mehlich single-buffer method. Aluminium extracted ,with 1M KCl was a poor predictor of lime requirement to pH, 5.5. In most of the soils tested, the actual amounts of lime required to reduce Al to a predetermined level far exceeded those calculated on the basis of 1 M KCl extractable Al values of untreated soils. Batch equilibration of soil : water suspensions containing Ca(OH)2 proved a reliable but relatively time-consuming method of determining lime requirement. All of the buffer methods were reasonably well correlated with lime requirement (0.61 < r2 < 0.82). Buffer methods which had a high initial buffer pH and a relatively high buffer strength were less well correlated with lime requirement than weaker buffers of lower initial pH. The Mehlich single-buffer method (initial pH 6.6) fitted both these latter criteria and gave good correlations with lime requirements to pHw 5.5 (r2 =0.78) and pHw 6.5 (r2 = 0.80). Compared with the single-buffer methods, neither of the double-buffer methods (which require two pH measurements) was better correlated with lime requirements.

Effects of increased levels of soil CaCO3 on Lupin (Lupinus angustifolius) growth and nutrition

Little published evidence exists which relates narrow-leafed lupin growth to lime levels in soils when compared with growth on a soil with minimal or zero levels of lime. This pot experiment measured lupin growth and nodulation plus plant levels of Ca and Fe by using mixtures of a gilgaid black earth soil with varying quantities of free lime. A sand control allowed a plant growth comparison at minimal levels of lime. Iron sequestrene was added to all treatments to eliminate iron chlorosis. Plants harvested 68 days after sowing showed adequate levels of Fe. However, plant height, branch number, shoot and root dry weight and nodulation were markedly lower for plants grown on the low lime depression soil than those from the sand. Further major reductions in all aspects of growth occurred with increasing levels of the mound (high lime) soil. These effects were strongly related to soil and plant Ca levels; it is suggested that poor lupin growth on highly calcareous soils may be related to adverse direct effects of Ca.

Poor soil aeration or excess soil CaCO3 induces Fe deficiency in lupins

The poor growth and chlorosis suffered by lupins when grown on fine-textured alkaline soils appears primarily related to Fe deficiency which is affected by the level of HCO3-; and CaCO3 in the soil.Plants of Lupinus angustifolius were grown on an alkaline, sandy clay loam which was either acidified or limed. Additionally, plants received either adequate water (field capacity) or excess water to adjust the aeration of the soil.Plant growth was closely related to the concentration of Fe within the young leaves. Liming the soil or watering above field capacity reduced the Fe concentrations in shoots, induced chlorosis and reduced growth. Chlorosis and reduced growth was not caused by Mn deficiency, even though treatments that reduced growth also reduced Mn concentrations in shoots.The lime chlorosis disorder in lupins therefore is primarily caused by an inability of the plants to obtain Fe in calcareous soils and not caused by Mn deficiency or by inactivation of Fe within the shoots.