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.

Sequestration of P fractions in the soils of an incipient ferralisation chronosequence on a humid tropical volcanic island

Background Phosphorus (P) is the limiting nutrient in many mature tropical forests. The ecological significance of declining P stocks as soils age is exacerbated by much of the remaining P being progressively sequestered. However, the details of how and where P is sequestered during the ageing in tropical forest soils remains unclear. Results We examined the relationships between various forms of the Fe and Al sesquioxides and the Hedley fractions of P in soils of an incipient ferralitic chronosequence on an altitudinal series of gently sloping benches on Green Island, off the southeastern coast of Taiwan. These soils contain limited amounts of easily exchangeable P. Of the sesquioxide variables, only Fe and Al crystallinities increased significantly with bench altitude/soil age, indicating that the ferralisation trend is weak. The bulk of the soil P was in the NaOH and residual extractable fractions, and of low lability. The P fractions that correlated best with the sesquioxides were the organic components of the NaHCO3 and NaOH extracts. Conclusions The amorphous sesquioxides, Feo and Alo, were the forms that correlated best with the P fractions. A substantial proportion of the labile P appears to be organic and to be associated with Alo in organic-aluminium complexes. The progression of P sequestration appears to be slightly slower than the chemical and mineralogical indicators of ferralisation.

The distribution of phosphorus from recycled fertilizers to different soil fractions determines the phosphorus availability in soil

Recycling of agricultural wastes to reduce mineral fertilizer input, in particular phosphorous (P), plays crucial role in sustainable agriculture production. Understanding the transformation of phosphorous (P) fractions and their bioavailability following soil application of different renewable P-contained fertilizers is very important for improving P use efficiency and reducing environmental risks. In this study, the effects of mineral P-fertilizer superphosphate and recycled P-fertilizers, i.e., poultry manure, cattle manure, maize straw and cattle bone meal, on their distribution to different soil P fractions, their transformation and the availability of soil P were determined by soil P sequential fractionation and 31P solution nuclear magnetic resonance (NMR). The results showed that addition of mineral P fertilizer, poultry manure and cattle manure increased P fixation in a red soil more than that in a fluvo-aquic soil. In both fluvo-aquic and red soils, cattle manure out-performed all other recycled P sources used in improving soil P availability. The concentration of Olsen-P in fluvo-aquic and red soils supplemented with cattle manure were increased by 41 %–380 % and 16 %–70 % than the other recycled P sources. A structural equation model (SEM) explained 95 % and 91 % of Olsen-P variation in fluvo-aquic and red soils, respectively. Labile P fractions had positive effects on Olsen-P of fluvo-aquic and red soils. 31P-NMR study showed that amount of orthophosphate was the main factor affecting the availability of P from different P sources. In summary, cattle manure was found to be a superior renewable source of P in improving bioavailable P in soil, and its use thus has considerable practical significance in P recycling.

Litter inputs and phosphatase activity affect the temporal variability of organic phosphorus in a tropical forest soil in the Central Amazon

Purpose The tropical phosphorus cycle and its relation to soil phosphorus (P) availability are a major uncertainty in projections of forest productivity. In highly weathered soils with low P concentrations, plant and microbial communities depend on abiotic and biotic processes to acquire P. We explored the seasonality and relative importance of drivers controlling the fluctuation of common P pools via processes such as litter production and decomposition, and soil phosphatase activity. Methods We analyzed intra-annual variation of tropical soil phosphorus pools using a modified Hedley sequential fractionation scheme. In addition, we measured litterfall, the mobilization of P from litter and soil extracellular phosphatase enzyme activity and tested their relation to fluctuations in P- fractions. Results Our results showed clear patterns of seasonal variability of soil P fractions during the year. We found that modeled P released during litter decomposition was positively related to change in organic P fractions, while net change in organic P fractions was negatively related to phosphatase activities in the top 5 cm. Conclusion We conclude that input of P by litter decomposition and potential soil extracellular phosphatase activity are the two main factors related to seasonal soil P fluctuations, and therefore the P economy in P impoverished soils. Organic soil P followed a clear seasonal pattern, indicating tight cycling of the nutrient, while reinforcing the importance of studying soil P as an integrated dynamic system in a tropical forest context.

Release and distribution changes of phosphorus in three alkaline sandy soils as a function of bone char applications

An incubation experiment was carried out to assess bone char application on the availability and distribution of phosphorus in agricultural alkaline sandy soils. Three alkaline agricultural sandy soils in Upper Egypt have been collected from Arab El-Awamer at Assiut governorate, West El-Minia at El-Minia governorate, and New Valley Governorate. 100 grams were taken from each soil under study and placed in a plastic jar. The bone char is applied at level 0.4 g jar-1 into these soils. This experiment was incubated at 23 ºC in the dark for periods of 7, 16, 35, 65, and 84 days and arranged in a completely randomized design with three replicates. The results revealed that bone char applications to the soils resulted in a significant positive increase in the availability of phosphorus affected by the soil type and incubation periods in Arab El-Awamer soil. The percentage of increase in available phosphorous after adding bone char compared to before incubation was as follows: Arab El-Awamer soil ˃New Valley soil ˃West El-Minia soil. The available phosphorous was negatively correlated with electrical conductivity (r=-0.288*), soluble calcium (r=-0.306*), and soluble sulfate (r=-0.413*). The concentrations of NH4Cl-Pi, NaHCO3-Pi, NaOH-Pi, HCl-Pi, residual-P fractions increased significantly in some soil types with applying bone char. The concentrations of available phosphorous in all soils under study were positively correlated with all phosphorus fractions. We conclude that bone char applications into P-poor soil are important to potentially enhance phosphorus availability. Bone char is considered a promising strategy in sustainable agriculture.

Influence of Soil Properties on P Pools and Its Effect on Forest Productivity in Mediterranean Calcareous Soils

Although soil phosphorus is essential for vegetation growth it is not always found in labile forms, hampering its absorption by plants, and is limited in forest ecosystems. This study explores soil P state and availability in calcareous soils, determining which processes affect its different pools and which soil parameters influence forest productivity of a Mediterranean pine species. We used a sequential fractionation method to determine P fractions in the soil according to their lability and their organic or inorganic nature. Those fractions were related to different soil and climatic parameters and to the site index in 32 Pinus halepensis plots of the National Spanish Forest Inventory. Soil texture, carbonates content, water retention capacity and organic matter substantially affected P fractions in the calcareous soils studied. Membrane extractable P was mainly influenced by organic matter-related parameters while the predominant P fraction in these soils, the primary P, was linked to the carbonates content. The biological mineralization processes played a key role in the soil P cycle. Total P, carbonates content, soil texture and water availability drove forest productivity in the studied plots.

Effect of biochar addition on legacy phosphorus availability in long-term cultivated arid soil

Background Continuous application of phosphorus (P) nutrient in association with its low recovery results in large amounts of P being accumulated in soil in different forms. Use of biochar can be a possible means to mobilize soil legacy P and increase its bioavailability. Therefore, the aim of this study was to identify the potential impact of a range of biochar types on P fractions in a long-term cultivated arid soil with high legacy P content. Methodology The soil was treated with biochar produced from four feedstock sources (BFS): sewage sludge (SSB), olive mill pomace (OPB), chicken manure (CMB), and date palm residues (DRB) pyrolyzed at 300, 500, or 700 °C in addition to an untreated control. The soil biochar mixture was incubated for 1 month followed by soil P fractionations using sequential chemical extraction to separate soil P into: labile (Resin-Pi, NaHCO3-Pi, NaHCO3-Po), moderately labile (NaOH-Pi, NaOH-Po), and non-labile (HCl-Pi and Residual-P) pools. Results Biochar addition clearly influenced most of the soil P fractions; however, the extent of this effect greatly varied depending on BFS and pyrolysis temperature (PT). The most evident biochar impact was observed with labile P pool, with the greatest increase being observed in NaHCO3-Pi fraction in most biochar treatments. Irrespective of PT, SSB and CMB were the most effective biochar type in increasing labile inorganic P; the SSB and CMB increased Resin-Pi by 77 and 206% and NaHCO3-Pi by 200 and 188%, respectively. In contrast, DRB made no changes in any P fraction. Differences in effects of biochar types on labile P is presumably related to the higher content of P in biowaste-based biochar compared to plant-based biochar which have much lower P content. The SSB, CMB, and OPB produced at low temperature reduced HCl-Pi content, indicating that these biochars may have stimulated organic matter decomposition and thereby dissolution of non-labile Ca-associated P to labile P forms. Conclusion Overall, biochar addition appeared to be an effective approach in enhancing legacy P availability in arid soil. However, further studies are necessary to verify these findings in the presence of plant and for a longer period. Graphic abstract

Phosphorus Dynamics in Sugarcane Fertilized With Filter Cake and Mineral Phosphate Sources

Organic residual material such as filter cake, combined with mineral phosphate fertilizers, may alter the soil phosphorus (P) bioavailability for sugarcane as a consequence of the competing effect in adsorption sites. This study aimed to quantify the changes in both the inorganic and organic soil P fractions as amended by phosphate fertilizer sources and filter cake and to link the P fractions to sugarcane response. An experiment was conducted in an Oxisol, in a randomized block design with factorial arrangement of 4 × 2, and three replications. Three P fertilizer sources (triple superphosphate, Araxá rock phosphate, and Bayóvar® reactive phosphate) plus a control (no P) were evaluated under both the presence and absence of filter cake. At the end of the second crop cycle, the following were measured: the cane yield, the tissue P content, and soil P fractions. All fertilizer sources were efficient in supplying P to sugarcane. Araxá rock phosphate generated a higher accumulation in moderately labile P, whereas the soluble triple superphosphate resulted in higher labile P. The filter cake, as a source of nutrients and organic matter, has an important contribution to maintain more available P for sugarcane absorption, especially when associated with triple superphosphate. The amount of P absorbed by sugarcane was correlated with the soil labile P (r = 0.58) and also with the inorganic P moderately labile (r = 0.42). Both fractions must be taken into account for a short- to medium-term availability of P for sugarcane in Oxisols.