Phosphorus Management Research Articles

Management of Nitrogen and Phosphorus in Castor Bean Culture

Management of Nitrogen and Phosphorus in Castor Bean Culture

Response of Groundnut Varieties to Phosphorus Management in Groundnut-Baby Corn Cropping Sequence

The experiment was conducted during 2019 and 2020 (March to August) at Regional Research Station, Bidhan Chandra Krishi Viswavidyalaya, Jhargram, West Bengal, India to find out the response of phosphorus management on growth and yield of groundnut varieties and its residual effect on succeeding baby corn. The three main plot treatments (variety- TAG 24, TG 51, TG 37A) and six subplot treatments of phosphorus dose were laid out in split plot design with three replications. Highest plant height (70.3 cm), number of branches plant-1 (8.5), crop growth rate (3.67 g m-2 day-1), pod yield (2007 kg ha-1), haulm yield (2876.22 kg ha-1), kernel yield (1360.76 kg ha-1) and oil yield (689.36 kg ha-1) were obtained with groundnut variety TG 51. Whereas phosphorus dose (100% RDF+PSB @ 25 g kg-1 of seed+FYM @ 2 t ha-1) provided highest value for the above characters. Interaction effect was significant for pod yield and kernel yield. The residual effect on succeeding baby corn was found maximum for variety TAG 24 and treatment (100% RDF+PSB @ 25 g kg-1 of seed+FYM @ 2 t ha-1) applied to previous groundnut. So, application of phosphorus @ 60 kg ha-1 along with P.S.B @ 25 g kg-1 of seed and F.Y.M @ 2 t ha-1 may be successful for groundnut variety TG 51 alone and TAG 24 in sequence with baby corn.

Reagentless electrochemically assisted desorption for selective phosphate recovery from wastewater: Proof of concept and mechanism

Adsorption is a promising technology for removing and recovering phosphorus (P) from wastewater. However, the chemical-intensive regeneration of adsorbents increases carbon emissions and introduces potential secondary pollution. Most existing approaches cannot achieve simultaneous P desorption and selective recovery. For this purpose, a new-type electrochemically assisted phosphate desorption and recovery (EPDR) process was investigated and developed for the efficient desorption and recovery of P and simultaneous regeneration of the adsorbent in situ. In the EPDR process, the adsorbent amorphous zirconium oxide (am-ZrO2) coated carbon felt (CF) was employed as a cathode in an anion-exchange membrane (AEM) water electrolysis cell for P adsorption/desorption and recovery. The P desorption and recovery efficiency from the adsorbent were over 90% at 3.5 V. It was found that the high concentration of OH– at the cathode surface derived from water splitting reaction and electrodialysis under the applied electric field was playing a critical role in the desorption process. Low concentrations of P in actual wastewater were effectively removed, concentrated and recovered under multiple adsorption–desorption cycles with easy-to-scale-up stacked EPDR. The nature of reagent-free, high efficiency and selectivity make EPDR the foundation for developing a cost-effective and green technology for sustainable phosphorus management.

Biomass Allocation and Nutrients Utilization in Wheat as Affected by Phosphorus Placement and Salt Stress

Phosphorus (P) management in wheat grown under saline soil conditions requires a better understanding of how P placement and salt stress affect spatial root distribution, plant agronomic performance, and nutrient utilization. A column culture experiment was conducted with two wheat genotypes, Alice and LX99, five P placements (‘Top Dressed High P’, TopHP; ‘Top Dressed Reduced P’, TopRP; ‘Deep Banded High P’, DeepHP; ‘Deep Banded Reduced P’, DeepRP; and ‘No P added’, −P), and two salt stress levels (‘salt stress’, +S; ‘non-salt stress’, −S) to investigate differences in biomass accumulation, nutrient utilization, and root distribution (0–20 cm, 20–40 cm, and 40–100 cm) among treatments. Deep P placement under non-salt stress increased root distribution at 20–40 cm soil depth for both genotypes compared to top P placement. P application under salt stress increased root weight at all three soil depths in both genotypes and P accumulation in aboveground plant parts (except for LX99 under TopRP). The highest P utilization efficiency occurred in Alice with TopRP and in LX99 with DeepRP under non-salt and salt stresses. Overall, a coordinated adaptation in allocating biomass between belowground and aboveground plant parts, along with altered nutrient utilization, was necessary to reach a growth compromise in response to P supply changes and salinity. Therefore, genotype, P placement depth, and soil salinity should be considered to improve wheat P utilization efficiency under saline conditions.

System-based management of phosphorus in a non-flooded rice-lentil system on alkaline soil

System-based management of phosphorus in a non-flooded rice-lentil system on alkaline soil

Influences of peanut hull-derived biochar, Trichoderma harzianum and supplemental phosphorus on hairy vetch growth in Pb- and Zn-contaminated soil.

In the present study, in order to improve the growth performance of hairy vetch (Vicia villosa Roth., Local landrace from Ardabil, Iran) seedlings grown in the soil contaminated with heavy metals Pb and Zn, our attention was directed toward the application of biochar, inoculation with conidial suspension of Trichoderma harzianum Rifai-T22 and management of phosphorus (P) nutrition. Heavy metal toxicity reduced leaf greenness, membrane stability index, maximum quantum yield of PSΙΙ (Fv/Fm), P concentration and uptake in plant tissues and root and shoot biomass, but increased Pb and Zn concentration and uptake in root and leaf, H2O2 and malondialdehyde content and CAT and POX activity in the leaves. The application of biochar, inoculation with Trichoderma fungus and P supplementation increased the shoot P content, which might contribute to the alleviation of P insufficiency and a subsequent elevation in P transfer to aboveground biomass, and eliminated the toxicity of heavy metal on hairy vetch plants, which was revealed in reducing oxidative stress and enhancing plant growth performance. The biochar considerably increased Zn immobilization, while being able to slightly stabilize Pb. Co-application of Trichoderma and 22mg P/kg soil (22P) increased the concentration and uptake of Zn in the roots and decreased the translocation of this element to the shoots, especially when biochar was not amended. Although the biochar and P inputs could compensate the negative Trichoderma effects, the results suggested that biochar application in combination with fungal inoculation and 22-P supplementation could not only increase hairy vetch growth performance but also decline heavy metal uptake to ensure the production of a forage crop in soils polluted with heavy metals based on the nutritional standards of livestock.

What are stakeholder views and needs for achieving phosphorus sustainability?

Our society depends on the effective management of phosphorus (P). Phosphorus is a key component of agricultural fertilizers to improve crop yields, and also plays a critical role in many industrial processes and consumer products. In the past decade, there have been numerous calls for innovative approaches to manage P more sustainably, as it is a nonrenewable resource that can adversely impact aquatic ecosystems from runoff and inefficiencies in P use. To develop more sustainable solutions that will ultimately be adopted, diverse stakeholder perspectives must be recognized, including those in industry, government, academia, non-governmental organizations, and other civil groups. This study responds to this need by identifying stakeholder views, needs, concerns, and challenges regarding P sustainability. An online survey was developed and deployed to individuals identified as P sustainability experts and professionals in the U.S. and abroad. Based on responses from 96 stakeholder participants from a range of sectors, areas of expertise, and geographies, we found that the vast majority of stakeholders considered current P use to be unsustainable and were very concerned about the ability to manage P sustainably. Stakeholder participants did not distinguish between urgent and long-term challenges, and perceived financial and regulatory issues to be of greatest importance. Stakeholder participants expressed a range of needs to improve P management systems, including improved management practices, new technologies, enhanced regulations, and better approaches for engagement. Outcomes from this work can help inform future research, engagement, and policy priorities to ensure sustainable P management solutions based on stakeholder-identified perspectives and needs.

Integrated application of phosphorus-accumulating bacteria and phosphorus-solubilizing bacteria to achieve sustainable phosphorus management in saline soils

The challenge of managing agricultural phosphorus (P) in saline regions entails both reducing leaching for environmental protection and maintaining soil available P levels for crop production, which could be achieved through functional microorganisms that can facilitate P transformation processes like P assimilation, inorganic P solubilization, and organic P mineralization. In this study, we proposed an integrated utilization of phosphorus-accumulating bacteria (PAB) and phosphorus-solubilizing bacteria (PSB) to reach the goal of alleviating P leaching while improving soil available P levels. The study conducted a microcosm experiment that combined a soil column test, soil incubation, and pot experiment to evaluate the effect of bacterial inoculants on soil P leaching, soil P availability, and plant P accumulation. The results showed that the application of PAB reduced 22.6 % of dissolved P leaching through the absorption of labile phosphate in the soil, and 17.3 % of particulate P leaching through the promoted soil aggregation. The integrated inoculation of PSB and PAB synergistically improved soil available P content by 18.3 % through the mineralization of soil organic P, and remarkably boosted wheat growth and its P accumulation. Microbial community analysis revealed that the integrated microbial treatment decreased the diversity of soil bacterial community and increased the abundance of native microbial species, i.g. Lysobacter and Ramlibacter, which were positively correlated with soil available P content and alkaline phosphatase level. In conclusion, the integrated microbial strategy based on halotolerant PAB and PSB has great potential for sustainable P management in saline areas and agricultural activities.

Conservation tillage and microbially mediated integrated phosphorus management enhance productivity, profitability and energy use efficiency of maize

AbstractSustainability of maize production systems is threatened by poor economic returns and resource intensiveness. Therefore, an experiment was conducted at the ICAR-Indian Agricultural Research Institute, New Delhi during 2016–17 to 2017–18 to assess the effect of tillage and microbial inoculantsintegrated phosphorus (P) management on productivity, quality, economic outcome and energy dynamics of maize. Three tillage practices viz., CT–R (conventional tillage with no residue), ZT–R (zero tillage with no residue) and ZT + R (zero tillage with wheat crop residue at 2.5 Mg/ha) were assigned in main plots and five P management practices viz., P1 (control–NK as per recommendation, but no P), P2 (17.2 kg P/ha), P3 (17.2 kg P/ha + PSB), P4 (17.2 kg P/ha + compost inoculants) and P5 (34.4 kg P/ha) were allocated in subplots in three times replicated split-plot design. The maximum grain yield (5.96 Mg/ha), protein content (9.13%), protein yield (546 kg/ha) and gross energy returns (209 × 103 MJ/ha) were recorded under ZT + R while higher benefit: cost ratio (B: C ratio – the amount of economic gain per unit investment) (1.53) and energy efficiency (12.5) was noticed under ZT–R. Among the P management practices, the application of 34.4 kg P/ha recorded the highest grain yield (6.45 Mg/ha), protein content (9.34%), protein yield (603 kg/ha), B: C ratio (1.65) and energy efficiency (10.1). The results suggested that the application of P at the rate of 34.4 kg/ha under ZT + R is an economically robust approach for the quality maize production in semi-arid region.

Phosphorus management is key to effective deployment of root ideotypes in complex soil environments

PurposeWe questioned how root ideotypes selected for deep or shallow root architecture function in complex environments with heterogeneous distributions of phosphorus (P), such as in many cropping systems in north-eastern Australia.MethodsWe used the rhizobox method to evaluate how contrasting genotypes of durum wheat and sorghum (wide and narrow root angle) responded to combinations of starter-P and deep P bands.ResultsAlthough we found evidence that root angle may influence spatio-temporal exploration for deep P bands, (early) plant access to P was the critical driver for plant growth. Without P, root system growth was retarded such that genotypic differences were hardly observed. Access to P boosted root exploration at depth by virtue of greater root system size, such that wide-angle genotypes with P outperformed narrow-angle ones without P. Plastic root responses to P benefited the expression of the broader root system architecture. We observed variation between species and individual parameters, but overall Starter-P and deep P bands tended to deliver complementary benefits when considering plant growth, P uptake, and phenological development together.ConclusionOur study highlights that nutritional constraints may limit the ability of root ideotypes to function in complex target environments. Development and deployment of root ideotypes should consider how local conditions (including soil nutrient distribution, physical and biological properties) influence crop phenotype and their ability to deliver the intended benefits. Within this, soil nutrient management is a critical determinant and an opportunity to influence the target environment.

Prevalence and factors associated with hyperphosphatemia in continuous ambulatory peritoneal dialysis patients: A cross-sectional study.

Hyperphosphatemia remains a major complication in patients with Continuous ambulatory peritoneal dialysis (CAPD) leading to increased morbidity and mortality. However, phosphorus management still has many challenges. This study aimed to investigate the prevalence and factors of hyperphosphatemia among continuous ambulatory peritoneal dialysis patients in a tertiary public hospital in Shanghai, China. The single-center cross-sectional study recruited end-stage renal failure patients who received continuous ambulatory peritoneal dialysis (CAPD) for at least 3 months. The participants aged 18-80 years had undergone CAPD between 1 July 2021 and 30 May 2022, in Shanghai, China.The patients' sociodemographic, clinical, and laboratory data were collected prospectively from medical records and via face-to-face interviews. A sample size of convenience decides the sample size. This study used the information-motivation-behavioral (IMB) skills model as a theoretical framework. The questionnaire included knowledge and behavior of diet and medication in patients with hyperphosphatemia of chronic kidney disease, self-efficacy for managing chronic disease, and social support rating scale. Univariate analysis and binary logistic regression were performed to identify the influencing factors of hyperphosphatemia by SPPS 27.0. In total, 141 CAPD patients (73% hyperphosphatemia) were included in the final analysis. In logistic regression analysis, dialysis vintage (OR: 0.975, 95%CI: 0.957-0.993), dialysis exchanges (OR: 0.317, 95%CI: 0.131-0.768), urine output (OR: 0.997, 95%CI: 0.995-0.999), serum albumin (OR: 1.166, 95%CI:1.008-1.349), serum creatinine (OR: 1.005, 95%CI: 1.001-1.008), hyperphosphatemia knowledge behavior score (OR: 0.888, 95%CI: 0.797-0.991), and social support level (OR: 0.841, 95%CI:0.765-0.925) were the influencing factors of hyperphosphatemia. Hyperphosphatemia is a frequent complication in CAPD patients. Dialysis vintage, dialysis exchanges, urine output, serum albumin, serum creatinine, hyperphosphatemia knowledge behavior, and social support were the associated factors of hyperphosphatemia in CAPD patients. It is crucial for healthcare providers to maintain phosphorus balance among CAPD patients using phosphorus management strategies.

192 Serum Phosphorus Management in Hemodialysis (HD) Patients Who Initiated Sucroferric Oxyhydroxide (SO) as a First-line Phosphate Binder Within the First Year of HD

192 Serum Phosphorus Management in Hemodialysis (HD) Patients Who Initiated Sucroferric Oxyhydroxide (SO) as a First-line Phosphate Binder Within the First Year of HD

Validation of a Phosphorus Food Frequency Questionnaire in Patients with Kidney Failure Undertaking Dialysis.

Nutritional guidelines recommended limiting dietary phosphorus as part of phosphorus management in patients with kidney failure. Currently, there is no validated phosphorus food frequency questionnaire (P-FFQ) to easily capture this nutrient intake. An FFQ of this type would facilitate efficient screening of dietary sources of phosphorus and assist in developing a patient-centered treatment plan. The objectives of this study were to develop and validate a P-FFQ by comparing it with the 24 hr multi-pass recall. Fifty participants (66% male, age 70 ± 13.3 years) with kidney failure undertaking dialysis were recruited from hospital nephrology outpatient departments. All participants completed the P-FFQ and 24 hr multi-pass recalls with assistance from a renal dietitian and then analysed using nutrient analysis software. Bland-Altman analyses were used to determine the agreement between P-FFQ and mean phosphorus intake from three 24 hr multi-pass recalls. Mean phosphorous intake was 1262 ± 400 mg as determined by the 24 hr multi pass recalls and 1220 ± 348 mg as determined by the P-FFQ. There was a moderate correlation between the P-FFQ and 24 hr multi pass recall (r = 0.62, p = 0.37) with a mean difference of 42 mg (95% limits of agreement: 685 mg; -601 mg, p = 0.373) between the two methods. The precision of the P-FFQ was 3.33%, indicating suitability as an alternative to the 24 hr multi pass recall technique. These findings indicate that the P-FFQ is a valid, accurate, and precise tool for assessing sources of dietary phosphorus in people with kidney failure undertaking dialysis and could be used as a tool to help identify potentially problematic areas of dietary intake in those who may have a high serum phosphate.

Periphyton Phosphorus Uptake in Response to Dynamic Concentrations in Streams: Assimilation and Changes to Intracellular Speciation.

Effective modeling and management of phosphorus (P) losses from landscapes to receiving waterbodies requires an adequate understanding of P retention and remobilization along the terrestrial-aquatic continuum. Within aquatic ecosystems, the stream periphyton can transiently store bioavailable P through uptake and incorporation into biomass during subscouring and baseflow conditions. However, the capacity of stream periphyton to respond to dynamic P concentrations, which are ubiquitous in streams, is largely unknown. Our study used artificial streams to impose short periods (48 h) of high SRP concentration on stream periphyton acclimated to P scarcity. We examined periphyton P content and speciation through nuclear magnetic resonance spectroscopy to elucidate the intracellular storage and transformation of P taken up across a gradient of transiently elevated SRP availabilities. Our study demonstrates that the stream periphyton not only takes up significant quantities of P following a 48-h high P pulse but also sustains supplemental growth over extended periods of time (10 days), following the reestablishment of P scarcity by efficiently assimilating P stored as polyphosphates into functional biomass (i.e., phospho-monoesters and phospho-diesters). Although P uptake and intracellular storage approached an upper limit across the experimentally imposed SRP pulse gradient, our findings demonstrate the previously underappreciated extent to which the periphyton can modulate the timing and magnitude of P delivery from streams. Further elucidating these intricacies in the transient storage potential of periphyton highlights opportunities to enhance the predictive capacity of watershed nutrient models and potentially improve watershed P management.

Effect of Nano-Phosphorus Formulation on Growth, Yield and Nutritional Quality of Wheat under Semi-Arid Climate

Appropriate phosphorus (P) management techniques increase yield and nutritional properties while minimizing environmental concerns. The widespread use of nano-fertilizers (NFs) in agriculture endangers soil and plants. It is vital to research the behavior of nano-phosphors (nano-P) on plant growth and quality, as well as their technique of interaction with soil properties in order to obtain key ecosystem benefits. With this in mind, a field experiment was conducted using wheat as a test crop to explore the impact of nano phosphorus (nano-P) on soil. The study’s goal was to examine how the foliar application of nano-P to wheat affects its growth, yield and nutrient concentration. Treatments consisted of: T1: 100% NPK (120:137:72 kg N:P2O5:K2O ha−1) by RDF (recommended dose of fertilizer); T2: 100% NPK by RDF + 2 foliar sprays of nano-P @ 494.21 mL ha−1; T3: 100% NK + 0% P (no foliar); T4: 100% NK + 75% P + 2 foliar sprays of nano-P @ 494.21 mL ha−1; T5: 100% NK + 50% P + 2 foliar sprays of nano-P @ 494.21 mL ha−1;T6: 100% NK + 0% P + 2 foliar sprays of nano-P @ 494.21 mL ha−1; T7: 100% NPK by RDF + 1 foliar spray of nano-P @ 494.21 mL ha−1; T8: 100% NK + 75% P + 1 foliar spray of nano-P @ 494.21 mL ha−1; T9: 100% NPK + 1 foliar spray of nano-P @ 494.21 mL ha−1; T10-100% NK + 75% P + 1 foliar spray of nano-P @ 494.21 mL ha−1. According to the findings, applying 100% NK + 75% P + 2 foliar applications of nano-P at the tillering and panicle initiation stages increased yield over 100% RDF by 37.1%. Additionally, the highest micronutrient concentration (Zn (36.4 mg kg−1), Cu (21.2 mg kg−1), Mn (22.9 mg kg−1) and Fe (61.1 mg kg−1)) in grain were noticed in T3 (100% NK + 0% P no foliar spray of nano-P) treatment, which was superior to T1 (100% NPK). Furthermore, foliar application of nano-P fertilizer in combination with different levels of diammonium phosphate (DAP) slightly increased the amount of N, P and K, as well as micronutrients in post-harvest soil. In summary, the use of 100% NK + 75% + 2 foliar applications of nano-P saved 25% recommendation dose P if supplied as nano-P as a form of phosphorus, and can be a suitable substitute for DAP, especially in smart agriculture, as it possibly reduces P leaching into groundwater, while maintaining or increasing wheat crop yield over the 100% RDF.

Potential of existing strategies to reduce net anthropogenic inputs of phosphorus to land in the United States

Improving phosphorus (P) management is important for both ecosystem protection and avoiding mineable P scarcity. In order to inform the development of impactful solutions to both of these issues, we assessed the potential of several specific management strategies to reduce demand for new mined P in fertilizers and supplements for livestock, thereby reducing net P inputs to land. The strategies assessed were variable rate fertilizer (VRF) application, improvements to P digestibility for livestock, efficient utilization of manure and wastewater treatment (WWT) P, and elimination of avoidable domestic food waste. The potential of these strategies to reduce net anthropogenic P inputs was assessed at the county level for the coterminous US using the commodity-specific net anthropogenic P and nitrogen inputs (CSNAPNI) model. The largest contributions toward eliminating NAPI in the US can come from efficient manure utilization either at national (30%–50% NAPI reduction) or county-level (21%–30% NAPI reduction). However, widespread adoption of VRF (10%–41% NAPI reduction), and all other strategies considered (5% or greater NAPI reductions each) could make significant contributions. In combinations of strategies that included VRF or P digestibility improvements, negative feedbacks occurred. VRF reduced demand for fertilizer, thereby reducing the potential for efficient manure and WWT P utilization at the county-level. P digestibility improvements in poultry and swine diets reduced the expected production of recoverable manure P by 36%, decreasing the total manure P that could be used to replace mined P fertilizer. However, P digestibility improvements also reduced county-level excess manure P by 25%. Prior studies have focused on quantifying P inputs or the potential of in-situ best management practices to reduce losses to water, but strategies to reduce P inputs are understudied.

Enhanced phosphorus-fertilizer-use efficiency and sustainable phosphorus management with intercropping

Enhanced phosphorus-fertilizer-use efficiency and sustainable phosphorus management with intercropping

Optimized multilateral crop trade patterns can effectively mitigate phosphorus imbalance among the involved countries

Phosphorus imbalance for cropland can greatly influence environmental quality and productivity of agricultural systems. Resolving cropland phosphorus imbalance may be possible with more efficient multilateral crop trade within the involved trading countries; however, the driving mechanisms are unclear. This study calculates phosphorus budgets in China and five central Asian countries and proposes two optimal multilateral crop trade models to mitigate the phosphorus imbalance. Results show that the current trading pattern between China and Central Asia is causing a phosphorus imbalance intensification. Phosphorus surpluses in China and Uzbekistan are 41.7 and 8.9 kg/ha, while Kazakhstan, Kyrgyzstan, Tajikistan, and Turkmenistan exhibit phosphorus deficits with the negative value of −0.7, −1.2, −0.8, and −0.8 kg/ha, respectively. However, under the optimal multilateral crop trade patterns, phosphorus budget of China and Central Asia will become balanced. Phosphorus imbalance intensification for China is reduced to −2525 and −2472 kt under the single- and bilevel-objective-based crop trades. In Kyrgyzstan, it will drop 61.5 % and 50.0 % and change to 321 and 417 kt under the two optimal crop trades. Moreover, changes of phosphorus imbalance mitigations for other central Asian countries range from 11.9 % to 28.2 %. This provides a scientific basis when establishing policies for strengthening optimal multilateral crop trading across the world to promote global phosphorus management.

Accumulation, Migration, and Transformation of Soil Phosphorus in Facility Agriculture and Its Influencing Factors

The aim of this study was to apply phosphorus fertilizer scientifically and reasonably and reduce the pollution risk to the facility agricultural environment. Taking the facility agriculture concentration area in Daxing District of Beijing as the research object, the phosphorus content in soil (0-100 cm) of the facility agriculture profile with different planting years was measured and analyzed to explore the characteristics of phosphorus accumulation, migration, and transformation. The results showed that the contents of total phosphorus and available phosphorus in the surface soil of facility agriculture varied widely, which was significantly higher than that in the surrounding grain field soil, which was mainly related to the amount of phosphorus applied by farmers in different planting years. With the increase in soil depth, the contents of total phosphorus and available phosphorus decreased gradually, showing surface aggregation ω (total phosphorus) ranging from 0.38 to 2.58 g·kg-1 and ω (available phosphorus) ranging from 1.60 to 256.00 mg·kg-1. With the increase in planting years, the contents of soil total phosphorus and available phosphorus first increased and then decreased, reached a peak in approximately 15 years, then gradually decreased, tended to be stable, and generally remained at a high level. Inorganic phosphorus was mainly concentrated in the surface soil of the facility agriculture, in which Ca-P accounted for the largest proportion of inorganic phosphorus, up to 98.38%; Ca10-P was the main form of Ca-P, up to 78.70% of Ca-P, and Ca2-P accounted for the smallest proportion, only 9.50% of Ca-P. The contents of different forms of inorganic phosphorus showed the vertical distribution characteristics of enrichment in the surface soil and a decrease downward. There were differences in the proportion of different forms of inorganic phosphorus to total phosphorus in different soil depths, in which the change in Ca-P was obvious, whereas the change in Fe-P and 0-P was not significant, indicating that the migration and transformation of Fe-P and O-P in the facility agricultural soil was poor, and the migration and transformation of inorganic phosphorus was mainly Ca-P. According to the correlation and path analysis, the direct path coefficient of Ca2-P to available phosphorus was the largest (0.787), which was not only the main source of soil available phosphorus but also the main form of inorganic phosphorus migration and transformation. Under the condition of protected cultivation, soil phosphorus showed a large accumulation trend, the availability of Ca10-P was low, and the accumulation was large. How to improve this portion of phosphorus sources is the key to the management of protected soil phosphorus.

Effects of phosphorus application on carbohydrate metabolism in cottonseed kernel during the key development period provided a new insight for phosphorus management in cotton production

Cottonseed provides abundant and high-quality raw materials for biodiesel, fine chemical, and other industries due to its rich oil, but phosphorus-deficient farmland and finite phosphate resource hinder its production. Cottonseed development is based on its carbohydrate, and exploring the response of cottonseed carbohydrate metabolism to phosphorus could contribute to optimizing phosphorus management in cotton production and continuously obtaining high-quality cottonseed. Here, the experiment on phosphorus rates [0 (phosphorus deficient), 100 (phosphorus critical), and 200 (phosphorus excess) kg P2O5 ha−1] was conducted using Lu 54 (low-phosphorus sensitive) and Yuzaomian 9110 (low-phosphorus tolerant) in a field containing 16.9 mg kg−1 available phosphorus to assess the effects of phosphorus on cottonseed yield, cottonseed total phosphorus, ash, and oil contents, carbohydrate metabolism related carbohydrate contents, and enzymes activities. The results showed that phosphorus application increased cottonseed yield and oil content by 32.4%−54.2% and 14.8%−20.1% on average, respectively, which could be attributed to the improvements in sucrose transport and hydrolysis in cottonseed kernel during 18–26 days post anthesis induced by higher total phosphorus content (17.1%−26.7%). During the key development period of cottonseed kernel, phosphorus application increased sucrose content (13.0%−19.4%) by increasing the expression of sucrose transporter genes, and promoted sucrose hydrolysis by elevating enzymes activities, especially sucrose synthase (11.2%−19.1%) in cottonseed kernel. Consequently, phosphorus application increased hexose levels in cottonseed kernel and thus provided more substrates for its development, which promoted the formation of cottonseed kernel biomass (6.2%−10.6%), cottonseed and oil yields. Additionally, carbohydrate metabolism in Lu 54 was more sensitive to phosphorus than Yuzaomian 9110 during the key development period, resulting in greater increases in cottonseed kernel biomass, cottonseed yield, and oil content for Lu 54. Notably, the increments generated by unit phosphate fertilizer on the above indicators attenuated markedly with phosphorus application. Based on sucrose content, the key substance, the critical phosphorus concentration in the subtending leaf to cotton boll (LPC) needed by the efficient operation of the key carbohydrate metabolic pathway was 0.38% for Lu 54 versus 0.34% for Yuzaomian 9110. This report first unveiled the key carbohydrate metabolic pathway regulated by phosphorus for cottonseed and oil yield formation and its demand for LPC during the key development period, providing a new insight for diagnosing and regulating phosphorus in cotton production.