The distribution and availability of phosphorus fractions in restored cut slopes soil aggregates along altitude gradient

The distribution and availability of phosphorus (P) fractions in restored cut slope soil aggregates along altitude gradients were studied. We examined soil aggregates total phosphorus (TP), available phosphorus (AP) and phosphorus activation coefficient (PAC), and discovered that there was no significant difference in TP at four altitudes (p> 0.05), but there was a significant difference in AP at 3009 m, 3347 m and 3980 m (p< 0.05). At 3009 m, 3347 m and 3654 m, the AP accumulation in small size aggregates were more advantageous. Overall, PAC dropped steadily as aggregate size increased, as shown by PAC (3654 m)> PAC (3347 m)> PAC (3009 m)> PAC (3980 m) in altitudes. In all particle size soil aggregates, total inorganic phosphorus (TPi) > total organic phosphorus (TPo) > residual phosphorus (R-P) at 3009 m, 3347 m and 3654 m; TPo> TPi> R-P at 3980 m. Through correlation and multiple stepwise regression analysis, we concluded that active NaHCO3-Pi was the main AP source. It was suggested that more attention should be paid to the ratio of small particle size aggregates, so as to increase soil AP storage. At low (3009 m) and high altitude (3980 m), inorganic P fertilizer and P activator were added into soil to improve the activation ability of soil P and the AP supply, so as to promote the healthy development of slope soils ecosystem.

Effect of long term fertilization on phosphorus dynamics in root zone environment under finger millet - Maize cropping sequence

In an agro-ecosystem, phosphorus (P) is found in organic and an inorganic form which includes soluble P, sorbed P and mineral bounded P. In soil, added P sources undergo various soil processes like mineralization, immobilization, precipitation, weathering, dissolution, sorption and desorption. For understanding the P dynamics in clay loam (Vertic Ustropept) soil, the present study was undertaken in P dynamics under rhizosphere and non-rhizosphere environment of maize in Long Term Fertilizer Experiment at Tamil Nadu Agricultural University, Coimbatore. The results revealed that the fractions of various pools of inorganic NaOH extractable Fe - P, H2SO4 extractable Ca- P, NH4F extractable Al- P, NH4Cl extractable Saloid P and Na citrate - Dithionate extractable Reductant soluble P were dominant in the non-rhizospheric soil than rhizospheric environment. The order of inorganic P fractions in the non-rhizospheric and rhizospheric region of the soil was found as Ca-P > Fe-P > Al-P > Reductant soluble-P > Saloid P and the knee-high stage of the non - rhizosphere soil recorded the highest inorganic as well organic P fractions. Irrespective of P fractions, Ca – P was recorded high (192.5 & 186.7 mg kg-1 ) followed by Fe - P (40.8& 34.9 mg kg-1) at a knee-high stage in non-rhizosphere and rhizosphere, respectively. Practising various nutrient management systems, application of 100% recommended dose of fertilizer along with FYM @ 10 t ha-1 (T8) recorded significant changes in all inorganic (Ca-P, Fe-P, Al-P, Reductant soluble-P, Saloid P), organic fractions and also Total P followed by 150% NPK (T3) in sandy clay loam soil. Nowadays, increasing demand for P fertilizer in India, judicious use of P fertilizer is important. Despite that, intensively cultivated soils have a lot of P reserves like organic and inorganic P pools and effective way of P transformation management could reduce the quantum of P fertilization in soil.

Addition of Phosphatases and Phytases to Mature Compost to Increase Available Phosphorus: A Short Study

Agriculture depends on fertilizers to provide nutrients for plants. Phosphorus (P) is one of these nutrients and is the second-most necessary for plant growth. Global production of P fertilizer is concentrated in Morocco, China and the United States. A large amounts of P resources are found in organic wastes that can be transformed through phosphate-solubilizing microorganisms during the composting process. In this study, we first determined the enzymatic activity of phosphatases and phytase from Pseudomonas aeruginosa ATC 15442. Second, we evaluated the mineralization of P in mature compost when inoculated with P. aeruginosa ATC 15442, phytases, a cocktail of phosphate-solubilizing enzymes and their combinations. Finally, we evaluated different concentrations of the cocktail trying to release more P in the compost. The results indicated that P. aeruginosa exuded alkaline phosphatases, acid phosphatase, neutral phosphatase and phytase. The enzymatic cocktail increased inorganic P (Pi) when added to the mature compost: this was able to release up to 95% more Pi in the compost compared to the amount of Pi released in the control compost. The current study demonstrated the importance of adding the cocktail to enhance Pi in mature compost; however, further studies are required to confirm the results and practical applications.

Cd and Zn Concentrations in Soil and Silage Maize following the Addition of P Fertilizer

Studies of soil Cd and Zn are often performed on sites that are contaminated or have deficient Zn conditions. Soil characteristics and crop management could impact the soil mobility and uptake of Cd and Zn, even when considering unpolluted Cd soils and adequate soil Zn levels. The concentrations of these two metals were assessed in soil and silage maize under five P fertilization treatments at two growth stages under low Cd and sufficient Zn conditions. Pearson correlation coefficients and stepwise linear regressions were calculated to investigate the soil characteristics influencing the bioavailable metal fraction in soil and the metal concentration in silage maize. P treatments did not impact Cd accumulation in maize; however, the Zn uptake was affected by P placement at the leaf development stage. From early development to maturity, the Cd level in maize decreased to 10% of the initial uptake, while the Zn level decreased to 50% of the initial uptake. This reduction in both metals may be attributed to a dilution effect derived from high biomass production. Silage maize could alleviate the initial Cd uptake while diminishing the depressant effect of P fertilizer on Zn concentration. Further research is required to understand the effect of P fertilizer on Cd uptake and its relation to Zn under field conditions at early and mature stages.

Dynamic and equilibrium precipitation of struvite from the concentrated cellulosic ethanol stillage

The phosphate rock mineral is the main source of P-fertilizer production. It is estimated to become depleted in next century. Thus, the recovery of phosphorus from waste streams have attracted great interest. The cellulosic ethanol production is seen more and more important in future. During the production of cellulosic ethanol, the phosphorus element is released from lignocellulosic biomasses and end up dissolved as phosphate ions in the stillage stream. In this study, the struvite (MgNH4PO4 · 6 H2O) recovery from the concentrated cellulosic ethanol stillage (ES) was conducted under room conditions with an initial pH at 7–9. The effect of Mg2+, PO43−, NH4+ and Ca2+ during struvite precipitation testes are investigated. The optimized pH value for struvite recovery is estimated at 8.5, by which 85% of PO43− and 46% of Mg2+ are removed from the liquid stream. The mass fraction of struvite in recovered crystal sample reaches 82 wt.%. The economic evaluation of struvite recovery from ES was also investigated. This work proves that the struvite is potentially to be recovered with high purity from the concentrated cellulosic ethanol stillage.

Physiological and Morphological Responses of Hydroponically Grown Pear Rootstock Under Phosphorus Treatment

Phosphorus (P) is an essential macronutrient for the growth and development of fruit trees, playing an important role in photosynthesis, nucleic acid synthesis, and enzyme activity regulation. The plasticity of plant phenotypic has been investigated in diverse species under conditions of P-deficiency or P-excess. Based on these researches, P level fluctuations in different species result in different characteristics of the response. Nevertheless, little is known about the response of pear seedling rootstock (Pyrus betulifolia Bunge) to the changing of P levels. To explore the effects of different levels of P on the growth of pear seedling rootstock, we performed the hydroponic assays to determine and analyze the biological indexes including growth parameters, photosynthetic rate, root and shoot morphological traits, and concentrations of macro- and micronutrients. The results show that either deficiency or excess of P inhibited the growth and development of pear seedling rootstock. Root growth (down 44.8%), photosynthetic rate (down 59.8%), and acid phosphatase (ACP) activity (down 44.4%) were inhibited under the P-deficiency conditions (0mM), compared with normal P conditions (1mM). On the other hand, dark green leaves, suppression of root elongation (down 18.8%), and photosynthetic rate (down 25%) were observed under regimes of excessive P, compared with normal P conditions (1mM). Furthermore, the root concentration of not only P, but also those of other mineral nutrients were affected by either P treatment. In brief, these results indicated that a careful choice of P fertilizer supply is crucial to ensuring normal growth and development of pear seedling rootstock.

Estimation of the P Fertilizer Demand of China Using the LePA Model

Modern phosphate (P) fertilizers are sourced from P rock reserves, a finite and dwindling resource. Globally, China is the largest producer and consumer of P fertilizer and will deplete its domestic reserves within 80 years. It is necessary to avoid excess P input in agriculture through estimating P demand. We used the legacy P assessment model (LePA) to estimate P demand based on soil P management at the county, regional, and country scales according to six P application rate scenarios: (1) rate in 2012 maintained; (2) current rate maintained in low-P counties and P input stopped in high-P counties until critical Olsen-P level (CP) is reached, after which rate equals P-removal; (3) rate decreased to 1–1.5 kg ha−1 year−1 in low-P counties after CP is reached and in high-P counties; (4) rate in each county decreased to 1–8 kg ha−1 year−1 after soil Olsen-P reached CP in low P counties; (5) rate in each county was kept at P-removal rate after reduction; (6) P input was kept at the rate lower than P-offtake rate after reduction. The results showed that the total P fertilizer demand of China was 750 MT P2O5, 54% of P fertilizer can be saved from 2013 to 2080 in China, and soil Olsen-P of all counties can satisfy the demand for high crop yields. The greatest potential to decrease P input was in Yangtze Plain and South China, which reached 60%. Our results provide a firm basis to analyze the depletion of P reserves in other countries.

Unravelling the Role of Rhizosphere Microbiome and Root Traits in Organic Phosphorus Mobilization for Sustainable Phosphorus Fertilization. A Review

Moving toward more sustainable sources for managing phosphorus (P) nutrition in agroecosystems, organic phosphorus (Po) derived from organic inputs and soil is increasingly considered to complement mineral P fertilizer. However, the dynamics of P added by organic input in soil-plant systems is still poorly understood and there is currently no clear information on how the Po composition of these amendments determines P availability through interactions with the soil microbiome and root traits. Here, we review the main mechanisms of rhizosphere microbiome and root traits governing the dynamics of organic input/soil-derived Po pools in the soil-plant system. We discuss the extent to which the major forms of Po derived from organic input/soil can be used by plants and how this could be improved to provide efficient utilization of organic inputs as potential P sources. We provide new insights into how a better understanding of the interactions between Po forms, root traits, and rhizosphere microbiomes can help better manage P fertilization, and discuss recent advances in the mobilization and recovery of Po from organic inputs. We then develop proposed strategies in agroecology that could be used to improve Po utilization, specifically by better linking plant traits and Po forms, and developing new cropping systems allowing more efficient Po recycling.