Identifying the critical phosphorus balance for optimizing phosphorus input and regulating soil phosphorus effectiveness in a typical winter wheat-summer maize rotation system in North China

Phosphorus(P)is a nonrenewable resource and a critical element for plant growth that plays an important role in improving crop yield.Excessive P fertilizer application is widespread in agricultural production,which not only wastes phosphate resources but also causes P accumulation and groundwater pollution.Here,we hypothesized that the apparent P balance of a crop system could be used as an indicator for identifying the critical P input in order to obtain a high yield with high phosphorus use efficiency(PUE).A 12-year field experiment with P fertilization rates of 0,45,90,135,180,and 225 kg P_(2)O_(5)ha^(-1)was conducted to determine the crop yield,PUE,and soil Olsen-P value response to P balance,and to optimize the P input.Annual yield stagnation occurred when the P fertilizer application exceeded a certain level,and high yield and PUE levels were achieved with annual P fertilizer application rates of 90-135 kg P_(2)O_(5)ha^(-1).A critical P balance range of 2.15-4.45 kg P ha^(-1)was recommended to achieve optimum yield with minimal environmental risk.The critical P input range estimated from the P balance was 95.7-101 kg P_(2)O_(5)ha^(-1),which improved relative yield(>90%)and PUE(90.0-94.9%).In addition,the P input-output balance helps in assessing future changes in Olsen-P values,which increased by 4.07 mg kg^(-1)of P for every 100 kg of P surplus.Overall,the P balance can be used as a critical indicator for P management in agriculture,providing a robust reference for limiting P excess and developing a more productive,efficient and environmentally friendly P fertilizer management strategy.

Assessment on Phosphorus Efficiency Characteristics of Soybean Genotypes in Phosphorus-Deficient Soils

A glasshouse study compared the growth and phosphorus （P） efficiency of 96 genotypes of soybean [Glycine max （L.） Merrill] in a P-deficient soil. The soybean genotypes differed greatly in growth, nodulation and P uptake after growing in the soil for 45 days, with shoot biomass ranging from 0.91 to 1.75 g per plant. The application of P improved biomass production, nodulation and P uptake and decreased root to shoot ratio, root length and surface area and P utilization efficiency. The 96 soybean genotypes were divided into 3 categories in P efficiency using the principal component analysis and cluster analysis, and 4 categories according to F values in combination with growth potentials. The Pefficient genotypes were associated with high biomass production, root to shoot ratio, root length and surface area and P uptake but low shoot to root P concentration ratio under P deficiency. The results indicate that there is a substantial genotypic variation in P efficiency in existing germplasm, and that P efficiency was correlated positively with dry weights of shoots and roots, ratio of root to shoot dry weight, root length and surface area, root P content and total P uptake. The shoot dry weight under P deficiency and relative shoot dry weight （deficient P/adequate P supply） are effective and simple indicators for screening P-efficient genotypes at the seedling stage.

Responses of Phosphorus Use Efficiency, Grain Yield, and Quality to Phosphorus Application Amount of Weak-Gluten Wheat

Phosphorus （P） is one of the most widely occurring nutrients for development and growth of wheat. In this study, the effects of P application amount on grain yield, protein content, and phosphorus use efficiency （PUE） were studied by agronomic management of P fertilizer on spring weak-gluten wheat （Triticum aestivum L.） grown under field conditions for 2 yr. The experiments were performed at five levels of P205 application amount, including 0, 72, 108, 144, and 180 kg ha-1. As a result, with increase in P fertilizer, grain yield, and P agricultural efficiency （AEp） increased in a quadratic equitation, but partial factor productivity of P （PFPp） decreased in a logarithmic eq. When 108 kg ha-1 P2Os was applied, the grain yield reached the highest level, but the protein content in gain was lower than 11.5%, a threshold for the protein content to evaluate weak-gluten wheat suitable for production of cake and biscuit. Yangmai 13 and Ningmai 9 could tolerate to higher P level of soils than Yangmai 9 that had more loss in grain yield when P fertilizer was over-applied. AEp had a concomitant relationship with grain yield and was a better descriptor for P use efficiency in the wheat. A high P use efficiency resulted in leaf area index （LAI）, increased chlorophyll content and photosynthetic rate, and stable acid phophatase （APase） activity to accumulate more dry matter after anthesis, which explained that the optimum P fertilizer increased grain yield and improved grain quality of weak-gluten wheat.

Effect of Phosphorus Fertilization to P Uptake and Dry Matter Accumulation in Soybean with Different P Efficiencies

Phosphorus （P） is an essential element for plant growth and yield. Improving phosphorus use efficiency of crops could potentially reduce the application of chemical fertilizer and alleviate environmental damage. Soybean （Glycine max （L.） Merr.） is sensitive to phosphorus （P） in the whole life history. Soybean cultivars with different P efficiencies were used to study P uptake and dry matter accumulation under different P levels. Under low P conditions, the P contents of leaf in high P efficiency cultivars were greater than those in low P efficiency cultivars at the branching stage. The P accumulation in stems of high P efficiency cultivars and in leaves of low P efficiency cultivars increased with increasing P concentration at the branching stage. At the late podding stage, the P accumulation of seeds in high and low P efficiency cultivars were 22.5 and 26.0%, respectively; and at the mature stage were 69.8 and 74.2%, respectively. In average, the P accumulation in whole plants and each organ was improved by 24.4% in high P efficiency cultivars compared to low P efficiency cultivars. The biomass between high and low P efficiency cultivars were the same under extended P condition, while a significant difference was observed at late pod filling stage. At the pod setting stage, the biomass of high P efficiency cultivars were significant greater （17.4%） than those of low P efficiency cultivars under high P condition. Meanwhile, under optimum growth conditions, there was little difference ofbiomass between the two types of cultivars, however, the P agronomic efficiency and P harvest index were significant higher in high P efficiency cultivars than those in low P efficiency cultivars.

Tolerance to low phosphorus in rice varieties is conferred by regulation of root growth

Phosphorus use efficiency(PUE)can be improved through cultivation techniques and breeding.However,little is known about rice(Oryza sativa L.)agronomic and physiological traits associated with high PUE.We characterized the agronomic and physiological traits of rice varieties with different tolerances to low phosphorus in nutrient solution.Two varieties with strong tolerance to low phosphorus(STVs)and two with weak tolerance(WTVs)were grown at normal(NP,control)and low phosphorus(LP,1/20 of NP)concentrations.Plants grown at LP produced significantly lower grain yield than those grown at NP.WTVs yields were lower than STVs yields.Compared to NP,LP significantly increased phosphorus translocation efficiency(PTE),internal phosphorus efficiency(IPE)and phosphorus harvest index(PHI).Under the LP condition,PTE and IPE were higher for STVs than for WTVs.LP also reduced tiller number,shoot biomass,leaf area index(LAI),leaf photosynthetic rate,and mean root diameter of both kinds of varieties at the main growth stages,but to a lower extent in STVs.LP significantly increased the number of productive tillers,root biomass,root-shoot ratio,root bleeding rate,and root acid phosphatase(RAP)activity.Total root length,root oxidation activity(ROA),and root total and active absorbing surface areas for STVs were significantly increased under LP,whereas the opposite responses were observed for WTVs.Total root length,ROA,root bleeding rate,root active absorbing surface area,and RAP activity were positively and significantly correlated with grain yield,PTE,and IPE.These results suggest that the tolerance of rice varieties to a low-phosphorus growth condition is closely associated with root growth with higher biomass and activity.

Effect of Phosphorus and Irrigation Levels on Yield,Water Productivity,Phosphorus Use Efficiency and Income of Lowland Rice in Northwest Pakistan

With decreasing availability of water for agriculture and increasing demand for rice production, an optimum use of irrigation water and phosphorus may guarantee sustainable rice production. Field experiments were conducted in 2003 and 2004 to investigate the effect of phosphorus and irrigation levels on yield, water productivity （WP）, phosphorus use efficiency （PUE） and income of low land rice. The experiment was laid out in randomized complete block design with split plot arrangements replicated four times. Main plot consisted of five phosphorus levels, viz. 0 （P0）, 50 （P50）, 100 （P100）, 150 （P15o）, and 200 （P200） kg/hm2, while subplots contained of irrigation times, i.e. 8 （I8）, 10 （I10）, 12 （I12）, and 14 （I14） irrigation levels, each with a water depth of 7.5 cm. Mean values revealed that P150 in combination with I10 produced the highest paddy yield （9.8 t/hm2） and net benefit （1 231.8 US$/hm2） among all the treatments. Phosphorus enhanced WP when applied in appropriate combination with irrigation level. The highest mean WP [13.3 kg/（hm2-mm）] could be achieved at Plso with 18 and decreased with increase in irrigation level, while the highest mean PUE （20.1 kg/kg） could be achieved at P100 with I10 and diminished with higher P levels. The overall results indicate that P150 along with I10 was the best combination for sustainable rice cultivation in silty clay soil.

Genome-Wide Expression Profile of Maize Root Response to Phosphorus Deficiency Revealed by Deep Sequencing

Phosphorus （P） is one of the three primary macronutrients that are required in large amounts for plant growth and development. To better understand molecular mechanism of maize and identify relevant genes in response to phosphorus deficiency, we used Solexa/Illumina＇s digital gene expression （DGE） technology to investigate six genome-wide expression profiles of seedling roots of the low-P tolerant maize inbred line 178. DGE studies were conducted at 6, 24 and 72 h under both phosphorus deficient and sufficient conditions. Approximately 3.93 million raw reads for each sample were sequenced and 6 816 genes exhibited significant levels of differential expressions in at least one of three time points in response to P starvation. The number of genes with increased expression increased over time from 6 to 24 h, whereas genes with decreased expression were more abundant at 72 h, suggesting a gradual response process for P deficiency at different stages. Gene annotations illustrated that most of differentially expressed genes （DEGs） are involved in different cellular and molecular processes such as environmental adaptation and carbohydrate metabolism. The expression of some known genes identified in other plants, such as those involved in root architecture, P metabolism and transport were found to be altered at least two folds, indicating that the mechanisms of molecular and morphological adaptation to P starvation are conserved in plants. This study provides insight into the general molecular mechanisms underlying plant adaptation to low-P stress and thus may facilitate molecular breeding for improving P utilization in maize.

A major quantitative trait locus controlling phosphorus utilization efficiency under different phytate-P conditions at vegetative stage in barley

Organic phosphorus（P） is an important component of the soil P pool, and it has been proven to be a potential source of P for plants. The phosphorus utilization efficiency（PUE） and PUE related traits（tiller number（TN）, shoot dry weight（DW）, and root dry weight） under different phytate-P conditions（low phytate-P, 0.05 mmol L^-1 and normal phytate-P, 0.5 mmol L^-1） were investigated using a population consisting of 128 recombinant inbred lines（RILs） at the vegetative stage in barley. The population was derived from a cross between a P-inefficient genotype（Baudin） and a P-efficient genotype（CN4027, a Hordeum spontaneum accession）. A major locus（designated Qpue.sau-3 H） conferring PUE was detected in shoots and roots from the RIL population. The quantitative trait locus（QTL） was mapped on chromosome 3 H and the allele from CN4027 confers high PUE. This locus explained up to 30.3 and 28.4% of the phenotypic variance in shoots under low and normal phytate-P conditions, respectively. It also explains 28.3 and 30.7% of the phenotypic variation in root under the low and normal phytate-P conditions, respectively. Results from this study also showed that TN was not correlated with PUE, and a QTL controlling TN was detected on chromosome 5 H. However, dry weight（DW） was significantly and positively correlated with PUE, and a QTL controlling DW was detected near the Qpue.sau-3 H locus. Based on a covariance analysis, existing data indicated that, although DW may affect PUE, different genes at this locus are likely involved in controlling these two traits.

Critical phosphorus concentrations in winter wheat genotypes with various phosphorus efficiencies

Under greenhouse conditions, a pot experiment was conducted to seek critical phosphorus concentrations of wheat genotypes with high and low phosphorus use efficiency. Results indicated that low efficient genotype was much more sensitive to phosphorus deficiency, with low or without phosphorus application, seed yield and dry matter of biomass were much lower. The yield of all the genotypes gradually got higher as application rate increased, but high efficient genotype——Lofflin produced relatively higher yields of seeds and biomass with low or without phosphorus input. Highly tolerate to low availability of soil phosphorus and efficient activation and absorption for soil unavailable phosphorus had been displayed. As application rates increased, yields of both genotypes were increased but high efficient genotype maintained stable while low efficient one showed continuously increase with remuneration decrease progressively. Critical phosphorus concentrations in high efficient genotypes of winter wheat were lower than that in low efficient ones and changed with various development stages, for example, at seedling state, the concentrations of high efficient genotype were 4.50—4.60 g/kg while low efficient one was 5.0 g/kg. They were 2.25—2.30 g/kg and 2.52 g/kg at flower stage, 1.96—2.05 g/kg and 2.15 g/kg at maturity respectively. But the values in seeds were reversal, higher in high efficient genotype(4.05—4.10 g/kg) than that in low efficient(3.90 g/kg). Therefore, phosphorus high efficient genotypes belong to the phosphorus resource saving type.

Differences in Phosphorus Absorption and Utilization Efficiency of Soybean in Mature Period under Phosphorus Stress

In this study, four phosphorus-inefficient soybean genotypes （1903, 1305, D17 and D18） and four phosphorus-efficient soybean genotypes （D31, D34, D37 and D38 ） were selected as experimental materials for soil culture experiment under high and low phosphorus treatments, to investigate the grain yield, phosphorus content, phosphorus uptake and the relationship between phosphorus utilization efficiency and phosphorus efficiency of soybean genotypes with different phos- phorus efficiency in mature period. According to the experimental results, under low phosphorus treatment, four phosphorus-efficient soybean genotypes exhibited significantly high phosphorus uptake in mature period, especially for D31 and D37; however, three phosphorus-efficient genotypes showed no advantages in adapta- bility of phosphorus utilization efficiency, while only I）31 exhibited high phosphorus utilization and absorption capacity. Correlation analysis and path analysis showed that phosphorus deficiency of soybean was mainly detemained by phosphorus absorption capacity, and phosphorus deficiency under （-P） treatment was sig- nificandy higher than （ ＋ P） treatment. Phosphorus uptake and phosphorus utilization efficiency posed great direct effects on phosphorus efficiency, and phosphorus uptake exhibited a greater contribution ; in addition, these two factors both posed small indirect effects. In mature period at reproductive growth stage, phosphorus absorption efficiency （phosphorus uptake） was the main variation source of phosphorus efficiency of various soybean genotypes in mature period. Therefore, strong phosphorus uptake and accumulation capacity of phosphorus-efficient soybean genotypes in mature period is an important nutrition foundation for the information of high grain yield.

Screening and identification of soybean varieties with high phosphorus efficiency at seedling stage

In order to simplify the workload and find a reliable method for screening soybeans with different phosphorus(P)efficiencies,47 soybean varieties were screened from 90 varieties according to yield under normal phosphorus,and 10 indicators including root phenotype,phosphorus utilization efficiency at the seedling stage and yield were measured.Through single-index cluster analysis,the performance value and relative value of the abovementioned indexes under low-phosphorus conditions were analyzed,and then,the combined indexes were analyzed by principal components method.The membership function method and the cluster analysis method was used to calculate and analyze the comprehensive score value.Three indexes of root P utilization efficiency(X_(1)),relative value of root P utilization efficiency(X_(2)),and root volume(X_(3))under low P at the seedling stage were selected as the most consistent with the yield screening results under low P condition,and the mathematical model of the comprehensive score value was obtained:D=1.218X_(1)t 0.320X_(2)t 0.007X_(3)-0.664(P=0.000,R^(2)=1.000).The comprehensive score can screen and identify the P efficiency of soybeans with fewer indexes in the early growth stages,which provides a more rapid and reliable mathematical model for screening and identifying a larger number of germplasm resources for P efficiency.

Molecular Characterization and Functional Analysis of OsPHY1,a Purple Acid Phosphatase (PAP)-Type Phytase Gene in Rice (Oryza sativa L.)

As a specific type of acid phosphatses, phytases play diverse roles in plants by catalazing the degradation of phytic acid and its derivatives. In this study, a rice phytase gene referred to OsPHY1 has been functionally characterized. OsPHY1 contains a 1 620 bp of open reading frame, encoding a 539-aa polypeptide. A conserve domain metallophosphatase （MPP） （MPP_PAPs）, generally harbored in phytase and purple acid phosphatases （PAP）, was identified in OsPHY1 （residue 194-398）. Phylogenetic analysis revealed that OsPHY1 shares high similarities with phytase genes and PAP-type genes that derived from diverse plant species. The OsPHY1 transcripts were detected to be abundant in germinating seeds, suggesting that this gene plays potential roles on degradation of seed phytic acid and its derivatives during the germination process. Biochemical analysis confirmed that OsPHY1 possesses strong catalytic activities on phytic acid-Na2, with optimal temperature of 57°C and suitable pH of 3.5. Based on transgene analysis, the putative role of OsPHY1 in plants on utilization of phytate was assessed. Under the condition that phytic acid-Na2 was used as sole P source, the OsPHY1-overexpressing tobacco plants behaved higher phytase activities, higher concentrations of Pi, more accumulative amount of total phosphorus, and much more improved growth traits than those of the control plants. Therefore, OsPHY1 is acted as an important component on degradation of the phytins during the seed germination process in rice. Also, OsPHY1 has a potential use on generation of elite crop germplasms with improved use efficiencies on phytate and its derivatives.

Experimental study on water-saving and emission-reduction effects of controlled drainage technology

Field experiments and laboratory analysis were carried out to determine the effects of controlled drainage（CTD） and conventional drainage（CVD） technologies on drainage volume, concentrations of NH4^＋ -N, NO3^-N, and total phosphorus（TP）, nitrogen and phosphorus losses, rice yield,and water utilization efficiency. Results show that CTD technology can effectively reduce drainage times and volume; NH4^＋ -N, NO3^-N, and TP concentrations, from the first to the fourth day after four rainstorms decreased by 28.7%e46.7%, 37.5%e47.5%, and 22.7e31.2%, respectively,with CTD. These are significantly higher rates of decrease than those observed with CVD. CTD can significantly reduce nitrogen and phosphorus losses in field drainage, compared with CVD; the reduction rates observed in this study were, respectively, 66.72%, 55.56%, and 42.81% for NH4^＋ -N, NO3^-N, and TP. Furthermore, in the CTD mode, the rice yield was cut slightly. In the CVD mode, the water production efficiencies in unit irrigation water quantity, unit field water consumption, and unit evapotranspiration were, respectively, 0.85, 0.48, and 1.22 kg/m^3, while in the CTD mode they were 2.91, 0.84, and 1.61 kg/m^3 din other words, 3.42, 1.75, and 1.32 times those of CVD. Furthermore, the results of analysis of variance（ANOVA） show that the indicators in both the CVD and CTD modes, including the concentrations of NH4^＋ -N, NO3^-N, and TP, the losses of NH4^＋ -N, NO3^-N, and TP, irrigation water quantity, and water consumption, showed extremely significant differences between the modes, but the rice yield showed no significant difference.

Assessment of Fertilising Properties of a Solid Digestate in Comparison with Undigested Cattle Slurry Applied to an Acidic Soil

The use of digestates or cattle slurries as fertilisers could contribute to the recycling of nutrients and organic matter, thus meeting the goals of the circular economy in agriculture. This work aims at evaluating the fertilising properties of a solid digestate (DG) in comparison with undigested cattle slurry (CS) and mineral fertilisation (MF). The experiment was performed in pots with ryegrass (Lolium multiflorum Lam.) grown in an acidic soil during a 163 days crop cycle. The results showed that throughout the crop cycle neither DG nor CS increased soil organic matter. DG significantly increased (P < 0.001) the sum of the soil exchangeable bases and soil P availability compared with CS or MF. Also, DG significantly increased (P < 0.05) the apparent P recovery of ryegrass (43%) compared with MF (27%). In the first cut, the ryegrass yield was higher in DG and CS than in MF, decreasing in the second and third cuts as a consequence of a decrease in N availability. Nevertheless, the fertilisation with DG or CS could replace the half amount of mineral N fertilisation, without a significant decrease in the ryegrass forage production. In addition, DG enables greater efficiency in the use of P than CS or MF.

Effects of transgenic soybean on growth and phosphorus acquisition in mixed culture system

Transgenic soybean plants overexpressing the Arabidopsis purple acid phosphatase gene AtPAP15 （OXp） or the soybean expansin gene GmEXPB2 （OXe） can improve phosphorous （P） efficiency in pure culture by increasing Apase secretion or changing root morphology. In this study, soybean‐soybean mixed cultures were employed to il uminate P acquisition among plants in mixed stands of transgenic and wild‐type soybean. Our results showed that transgenic soybean plants were much more competitive, and had greater growth and P uptake than wild‐type soybean in mixed culture in both low P calcareous and acid soils. Furthermore, OXe plants had an advantage in calcareous soils when mixed with OXp, whereas the latter performed much better in acid soils. In soybean‐maize mixed culture, transgenic soybean had no impact on maize growth compared to controls in both acid and calcareous soils with different P conditions. As for soybean in＆amp;nbsp;mixed culture, OXp plants had no significant advantages regardless of P availability or soil type, while P efficiency improved in OXe in calcareous soils compared to controls. These results imply that physiological traits could be easily affected by the mixed maize. Transgenic soybean plants with enhanced root traits had more competitive advantages than those with improved root physiology in mixed culture.

Characterization of Two Putative Protein Phosphatase Genes and Their Involvement in Phosphorus Efficiency in Phaseolus vulgaris

Protein dephosphorylation mediated by protein phosphatases plays a major role in signal transduction of plant responses to environmental stresses. In this study, two putative protein phosphatases, PvPS2：1 and PvPS2：2 were identified and characterized in bean （Phaseolus vulgaris）. The two PvPS2 members were found to be localized to the plasma membrane and the nucleus by transient expression of PvPS2：GFP in onion epidermal cells. Transcripts of the two PvPS2 genes were significantly increased by phosphate （P1） starvation in the two bean genotypes, G19833 （a P-efficient genotype） and DOR364 （a P-inefficient genotype）. However, G19833 exhibited higher PvPS2：1 expression levels than DOR364 in both leaves and roots during P1 starvation. Increased transcription of PvPS2：1 in response to P1 starvation was further verified through histochemical analysis of PvPS2：I promoter fusion b-glucuronidase （GUS） in transgenic Arabidopsis plants. Analysis of PvPS2：1 overexpression lines in bean hairy roots and Arabidopsis showed that PvS2：1 was involved in root growth and P accumulation. Furthermore, expression levels of two P1 starvation responsive genes were upregulated and the APase activities were enhanced in the overexpressing PvPS2：1 Arabidopsis lines. Taken together, our results strongly suggested that PvPS2：1 positively regulated plant responses to P1 starvation, and could be further targeted as a candidate gene to improve crop P efficiency.

Plant adaptation to low phosphorus availability:Core signaling,crosstalks,and applied implications

Phosphorus(P)is an essential nutrient for plant growth and reproduction.Plants preferentially absorb P as orthophosphate(Pi),an ion that displays low solubility and that is readily fixed in the soil,making P limita-tion a condition common to many soils and Pi fertilization an inefficient practice.To cope with Pi limitation,plants have evolved a series of developmental and physiological responses,collectively known as the Pi starvation rescue system(PSR),aimed to improve Pi acquisition and use efficiency(PUE)and protect from Pi-starvation-induced stress.Intensive research has been carried out during the last 20 years to un-ravel the mechanisms underlying the control of the PSR in plants.Here we review the results of this research effort that have led to the identification and characterization of several core Pi starvation signaling components,including sensors,transcription factors,microRNAs(miRNAs)and miRNA inhibitors,kinases,phosphatases,and components of the proteostasis machinery.We also refer to recent results revealing the existence of intricate signaling interplays between Pi and other nutrients and antagonists,N,Fe,Zn,and As,that have changed the initial single-nutrient-centric view to a more integrated view of nutrient homeostasis.Finally,we discuss advances toward improving PUE and future research priorities.

Phosphorus use efficiency and fertilizers:future opportunities for improvements

The continued supply of phosphate fertilizers that underpin global food production is an imminent crisis.The rock phosphate deposits on which the world depends are not only finite,but some are contaminated,and many are located in geopolitically unstable areas,meaning that fundamental changes will have to take place in order to maintain food production for a growing global population.No single solution exists,but a combination of approaches to phosphorus management is required not only to extend the lifespan of the remaining non-renewable rock phosphate reserves,but to result in a more efficient,sustainable phosphorus cycle.Solutions include improving the efficiency of fertilizer applications to agricultural land,alongside a better understanding of phosphorus cycling in soil-plant systems,and the interactions between soil physics,chemistry and biology,coupled with plant traits.Opportunities exist for the development of plants that can access different forms of soil phosphorus(e.g.,organic phosphorus)and that use internal phosphorus more efficiently.The development of different sources of phosphorus fertilizers are inevitably required given the finite nature of the rock phosphate supplies.Clear opportunities exist,and it is now important that a concerted effort to make advances in phosphorus use efficiency is prioritized.

Phosphorus supply and management in vegetable production systems in China

Vegetable production systems involve high rates of chemical and organic fertilizer applications,leading to significant P accumulation in vegetable soils,as well as a decrease in P use efficiency(PUE),which is one of the key limiting factors in vegetable production.This review introduces the vegetable production systems in China and their fertilization status,and analyzes probable causes of overfertilization of vegetable fields.Poorly developed root systems and high P demand have led to the need to maintain much higher available P concentrations in the root zone for regular growth of vegetables,which might necessitate higher phosphate fertilizer input than the plants require.Research on strategies to improve vegetable PUE and the mechanisms of these strategies are summarized in this review.Increasing the P uptake by vegetables by supplying P during the critical growth stage and effectively utilizing the accumulated P by optimizing the C:P ratio in soils can substantially increase PUE.These advances will provide a basis for improving PUE and optimizing phosphate fertilizer applications in vegetable production through regulatory measures.In addition,some policies are recommended that could ensure the safety of vegetables and improve product quality.This review also aims to improve understanding of P cycling in vegetable fields and assist in the development of best practices to manage P reserves globally.

Genetic study and molecular breeding for high phosphorus use efficiency in maize

Phosphorus is the second most important macronutrient after nitrogen and it has many vital functions in the life of plants.Most soils have a low available P content,which has become a key limiting factor for increasing crop production.Also,low P use efficiency(PUE)of crops in conjunction with excessive application of P fertilizers has resulted in serious environmental problems.Thus,dissecting the genetic architecture of crop PUE,mining related quantitative trait loci(QTL)and using molecular breeding methods to improve high PUE germplasm are of great significance and serve as an efficient approach for the development of sustainable agriculture.In this review,molecular and phenotypic characteristics of maize inbred lines with high PUE,related QTL and genes as well as low-P responses are summarized.Based on this,a breeding strategy applying genomic selection as the core,and integrating the existing genetic information and molecular breeding techniques is proposed for breeding high PUE maize inbred lines and hybrids.