Phosphorus uptake of rice plants is affected by phosphorus forms and physicochemical properties of tropical weathered soils

Kuo S.

Andriamananjara A., Rakotoson T., Razanakoto O.R., Razafimanantsoa M.-., Rabeharisoa L., Smolders E.

A vast upland area in Madagascar remains uncultivated because of erratic rainfall and because of the low fertility of the soils that are highly weathered and depleted in available phosphorus (P). This study was set up to identify to what extent farmyard manure (FYM) can overcome P deficiency and increase the use efficiency of mineral P (TSP). Rainfed rice was grown with soybean in rotation (two fields) in three subsequent seasons with factorial supplies of FYM and TSP (both applied in planting hole) with blanket N&K doses. The low and unresponsive rice grain yields (

Schut A.G., Traore P.C., Blaes X., de By R.A.

Agricultural intensification and efficient use and targeting of fertilizer inputs on smallholder farms is key to sustainably improve food security. The objective of this paper is to demonstrate how high-resolution satellite and unmanned aerial vehicle (UAV) images can be used to assess the spatial variability of yield, and yield response to fertilizer. The study included 48 and 50 smallholder fields monitored during the 2014 and 2015 cropping seasons south-east of Koutiala (Mali), cropped with the five major crops grown in the area (cotton, maize, sorghum, millet and peanuts). Each field included up to five plots with different fertilizer applications and one plot with farmer practice. Fortnightly, in-situ in each field data were collected synchronous with UAV imaging using a Canon S110 NIR camera. A concurrent series of very high-resolution satellite images was procured and these images were used to mask out trees. For each plot, we calculated vegetation index means, medians and coefficients of variation. Cross-validated general linear models were used to assess the predictability of relative differences in crop yield and yield response to fertilizer, explicitly accounting for the effects of fertility treatments, between-field and within-field variabilities. Differences between fields accounted for a much larger component of variation than differences between fertilization treatments. Vegetation indices from UAV images strongly related to ground cover (R2 = 0.85), light interception (R2 = 0.79) and vegetation indices derived from satellite images (R2 values of about 0.8). Within-plot distributions of UAV-derived vegetation index values were negatively skewed, and within-plot variability of vegetation index values was negatively correlated with yield. Plots on shallow soils with poor growing conditions showed the largest within-plot variability. GLM models including UAV derived estimates of light interception explained up to 78% of the variation in crop yield and 74% of the variation in fertilizer response within a single field. These numbers dropped to about 45% of the variation in yield and about 48% of the variation in fertilizer response when lumping all fields of a given crop, with Q2 values of respectively 22 and 40% respectively when tested with a leave-field-out procedure. This indicates that remotely sensed imagery doesn’t fully capture the influence of crop stress and management. Assessment of crop fertilizer responses with vegetation indices therefore needs a reference under similar management. Spatial variability in UAV-derived vegetation index values at the plot scale was significantly related to differences in yields and fertilizer responses. The strong relationships between light interception and ground cover indicate that combining vertical photographs or high-resolution remotely sensed vegetation indices with crop growth models allows to explicitly account for the spatial variability and will improve the accuracy of yield and crop production assessments, especially in heterogeneous smallholder conditions.

Shehu B., Merckx R., Jibrin J., Kamara A., Rurinda J.

Nishigaki T., Sugihara S., Kobayashi K., Hashimoto Y., Kilasara M., Tanaka H., Watanabe T., Funakawa S.

Soil phosphorus (P) forms have been practically defined as chemically fractionated pools. A knowledge of the abundance and diversity of P forms in soil, and the factors affecting them, will lead to...

Nawara S., Van Dael T., Merckx R., Amery F., Elsen A., Odeurs W., Vandendriessche H., Mcgrath S., Roisin C., Jouany C., Pellerin S., Denoroy P., Eichler-Löbermann B., Börjesson G., Goos P., et. al.

Summary Most soil tests for available phosphorus (P) perform rather poorly in predicting crop response. This study was set up to compare different established soil tests in their capacity to predict crop response across contrasting types of soil. Soil samples from long-term field experiments, the oldest >100 years old, were collected in five European countries. The total number of soil samples (n = 218), which differed in cropping and P treatment, and originated from 11 different soil types, were analysed with five tests: ammonium oxalate (Ox), ammonium lactate (AL), Olsen P, 0.01 m CaCl2 and the diffusive gradient in thin film (DGT). The first three tests denote available P quantity (Q), whereas the last two indicate P intensity (I) of the soil solution. All five tests were positively related to the crop yield data (n = 317). The Q-tests generally outperformed I-tests when evaluated with goodness of fit in Mitscherlich models, but critical P values of the I-tests varied the least among different types of soil. No test was clearly superior to the others, except for the oxalate extraction, which was generally poor. The combination of Q- and I-tests performed slightly better for predicting crop yield than any single soil P test. This Q + I analysis explains why recent successes with I-tests (e.g. DGT) were found for soils with larger P sorption than for those in the present study. This systematic evaluation of soil tests using a unique compilation of established field trials provides critical soil P values that are valid across Europe. Highlights We compared soil P tests for predicting crop response across contrasting soil types. No test was clearly superior to the others except for the oxalate extraction, which was generally poor. This study suggests that intensity tests do not perform markedly better than quantity tests. The evaluation of soil P tests on this unique dataset provided critical soil P values across Europe.

George T.S., Giles C.D., Menezes-Blackburn D., Condron L.M., Gama-Rodrigues A.C., Jaisi D., Lang F., Neal A.L., Stutter M.I., Almeida D.S., Bol R., Cabugao K.G., Celi L., Cotner J.B., Feng G., et. al.

The dynamics of phosphorus (P) in the environment is important for regulating nutrient cycles in natural and managed ecosystems and an integral part in assessing biological resilience against environmental change. Organic P (Po) compounds play key roles in biological and ecosystems function in the terrestrial environment being critical to cell function, growth and reproduction. We asked a group of experts to consider the global issues associated with Po in the terrestrial environment, methodological strengths and weaknesses, benefits to be gained from understanding the Po cycle, and to set priorities for Po research. We identified seven key opportunities for Po research including: the need for integrated, quality controlled and functionally based methodologies; assessment of stoichiometry with other elements in organic matter; understanding the dynamics of Po in natural and managed systems; the role of microorganisms in controlling Po cycles; the implications of nanoparticles in the environment and the need for better modelling and communication of the research. Each priority is discussed and a statement of intent for the Po research community is made that highlights there are key contributions to be made toward understanding biogeochemical cycles, dynamics and function of natural ecosystems and the management of agricultural systems.

Menezes-Blackburn D., Giles C., Darch T., George T.S., Blackwell M., Stutter M., Shand C., Lumsdon D., Cooper P., Wendler R., Brown L., Almeida D.S., Wearing C., Zhang H., Haygarth P.M.

Phosphorus (P) fertilizer is usually applied in excess of plant requirement and accumulates in soils due to its strong adsorption, rapid precipitation and immobilisation into unavailable forms including organic moieties. As soils are complex and diverse chemical, biochemical and biological systems, strategies to access recalcitrant soil P are often inefficient, case specific and inconsistently applicable in different soils. Finding a near-universal or at least widely applicable solution to the inefficiency in agricultural P use by plants is an important unsolved problem that has been under investigation for more than half a century. In this paper we critically review the strategies proposed for the remobilization of recalcitrant soil phosphorus for crops and pastures worldwide. We have additionally performed a meta-analysis of available soil 31P–NMR data to establish the potential agronomic value of different stored P forms in agricultural soils. Soil inorganic P stocks accounted on average for 1006 ± 115 kg ha−1 (57 ± 7%), while the monoester P pool accounted for 587 ± 32 kg ha−1 (33 ± 2%), indicating the huge potential for the future agronomic use of the soil legacy P. New impact driven research is needed in order to create solutions for the sustainable management of soil P stocks.

Kihara J., Nziguheba G., Zingore S., Coulibaly A., Esilaba A., Kabambe V., Njoroge S., Palm C., Huising J.

Improved understanding of soil fertility factors limiting crop productivity is important to develop appropriate soil and nutrient management recommendations in sub-Saharan Africa. Diagnostic trials were implemented in Kenya, Malawi, Mali, Nigeria and Tanzania, as part of the African Soils Information Service (AfSIS) project, to identify soil fertility constraints to crop production across various cropping systems and soil fertility conditions. In each country, one to three sites of 10 km × 10 km were included with each site having 12-31 field trials. The treatments tested included a control, an NPK treatment, three treatments in which the N, P and K nutrients were omitted one at a time from the NPK treatment, and three treatments in which secondary and micronutrients (Ca, Mg, S, Zn and B) simply referred here as multi-nutrients, manure and lime were added to the NPK. The field trials were conducted for 1-2 seasons; the test crop was maize except in Mali where sorghum was used. Nitrogen was limiting in all sites and generally the most limiting nutrient except in Sidindi (Kenya) and Kontela (Mali) where P was the most limiting. The general pattern in Kiberashi (Tanzania) shows none of the nutrients were limiting. K is mainly limiting in only one site (Mbinga) although incidences of K limitation were seen in almost all sites. Addition of multi-nutrients and manure further improved the yields of NPK in most sites. Cluster analyses revealed that maize crop in 11% of fields were highly responsive to nitrogen application, 25% (i.e., 21% poor and 4% fertile) 'non-responsive' to any nutrient or soil amendment, 28% being 'low responsive' and 36% of 'intermediate response'. This study indicates that constraints to crop production vary considerably even within a site, and that addressing limitations in secondary and micronutrients, and increasing soil carbon can improve response to fertilizers. For sustainable crop production intensification in smallholder farming systems in SSA, there is need to develop management strategies to improve efficiency of fertilizer use and of other inputs, recognizing the site-specific nutrient response patterns at various spatial scales.

Chassé A.W., Ohno T.

The competition between orthophosphate and water-extractable organic matter (WEOM) for adsorption to iron (oxy)hydroxide mineral surfaces is an important factor in determining the plant bioavailability of P in soils. Chemical force spectroscopy was used to determine the binding force between orthophosphate and iron (oxy)hydroxide that was coated onto atomic force microscopy (AFM) tips and adsorbed with WEOM. The force measurements were conducted at pH 4.65 and 0.02 M ionic strength which are representative of typical acid soil solutions. The chemical composition of the WEOM was determined by ultrahigh resolution electrospray ionization Fourier transform ion cyclotron mass spectrometry. The results indicate a correlation between aromatic WEOM molecules that are greater than 600 Da and the reduced binding force of orthophosphate to WEOM-adsorbed iron (oxy)hydroxide AFM tips suggesting that the molecular mass of aromatic WEOM molecules plays a critical role in regulating the WEOM-P interactions with surface functional groups of minerals. Based on the results of this study, we show the importance of obtaining a detailed, molecular-scale understanding of soil processes that can help develop better management strategies to reduce waste of limited P resources and adverse environmental impacts. Specifically, soil amendments with greater content of high molecular mass aromatic components may positively affect dissolved P use efficiency in soils by maintaining P in soil solution.

Dogbe W., Sogbedji J.M., Buah S.S.

A multi-location study was conducted to assess the nitrogen (N), phosphorous (P) and potassium (K) requirements of lowland rice (Oryza sativa L.) for a local variety Digang cultivated in the northern Savannahs of Ghana and offer site specific nutrient recommendations. Ten on-farm nutrient omission trials involving five rates of N, P and K combinations were conducted during 2010 cropping season in Sudan and Guinea Savannah agro-ecological zones. The treatments (kg/ha as N, P2O5 and K2O) comprised 0-0-0 (control), 0-90-90 (zero N), 90-0-90 (zero P), 90-90-0 (zero K), 90-90-90 (NPK). Grain yields were increased by applying fertilizer N, P and K in sufficient amounts (90 N, 90 P2O5 and 90 K2O kg/ha) to overcome deficiencies and maintain soil fertility. Nitrogen was a major limiting nutrient in the irrigated and rain fed lowlands in the northern Savannahs of Ghana. The N-limited yields varied between 832 and 1875 kg/ha, suggesting variability of N supplying capacity of the experimental plots. The impact of omitting N was different among the locations with the irrigated lowlands ecosystems in the Sudan Savannah that recorded the highest yield loss due to N omission and Guinea Savannah the least. Higher level of fertilizer N (118 kg/ha) was required in the irrigated lowland in the Sudan Savannah to achieve maximum yield compared with 52 to 79 kg N/ha in the rain fed lowlands of Guinea Savannah. Potash fertilizers have little effect on yield, especially in irrigated lowlands in the Sudan Savannah. Grain yield reductions due to nutrient deficiencies were more severe in the Upper West region than in Upper East region and Northern region. Higher levels of N in irrigated lowland ecosystems in the Sudan Savannah and higher P and K may be required in Upper West region in the Guinea Savannah than recommended for achieving higher yields on a sustainable basis.

Randriamanantsoa L., Frossard E., Oberson A., Bünemann E.K.

Mineralization of organic phosphorus (Po) may be of great importance for plant nutrition in soils containing very little available inorganic phosphorus (Pi). Gross organic P mineralization rates can be quantified by an isotopic dilution method using 33P labeling of soil. However, its application remains a challenge in tropical soils in which the concentration of phosphate ions in the soil solution is below the detection limit of traditional colorimetric methods. This limitation can potentially be overcome by the hexanol concentration method, which uses hexanol to concentrate the blue-colored phosphomolybdate complex from large volumes. We applied the isotopic dilution method in combination with the hexanol concentration method to a Ferralsol from the highlands of Madagascar which had been preincubated in the presence or absence of plant residues for 90 days before the start of the experiment. The limits of detection (DL) and quantification (QL) of the gross Po mineralization rate were 0.2 and 0.7 mg P kg− 1 soil day− 1, respectively. Basal gross Po mineralization rates after 7 days of incubation were 0.8 ± 0.5 and 1.7 ± 0.2 mg P kg− 1 soil day− 1 in non-amended and residue-amended soils, respectively. These rates are plausible, suggesting that the isotopic dilution method is applicable in highly weathered tropical soils with Pi concentrations in the soil solution below the detection limit of traditional colorimetric methods. Net Po mineralization which sustains the plant available P pool remains to be quantified. Gross and net Po mineralization rates should now be assessed in highly weathered soils under a range of land uses.

Nziguheba G., Zingore S., Kihara J., Merckx R., Njoroge S., Otinga A., Vandamme E., Vanlauwe B.

Current efforts in combating food insecurity in sub-Saharan Africa (SSA) focus on agricultural intensification. Given the high soil nutrient depletions, replenishing soil fertility is a major component of such efforts. One of the key nutrients limiting crop production is phosphorus (P). Overcoming P deficiency in smallholder farming in SSA faces many challenges, mainly because the causes of P deficiencies vary, and viable options to replenish soil P have limitations. In some areas, P deficiency is associated with a low P reserve, while in others, it results from a high soil P-adsorption capacity. Numerous studies have focused on developing approaches and strategies with potential to replenish soil P or improve its availability to crops. This paper highlights approaches and strategies that have been studied, including the use of soluble P fertilizers, phosphate rocks and organic resources. The contribution of soluble P fertilizers is mainly limited by their high cost, while most phosphate rocks are not mined. Replenishing P through organic resources is constrained by their often low P content and inadequate availability in smallholder farms. Optimizing the P use efficiency appears as the most plausible target pending an increased accessibility of P sources to farmers. Practices towards this optimization include strategic crop sequences and P allocation to crops, use of P-efficient genotypes, and targeting the residual P. Research is needed towards gaps in understanding processes governing benefits associated with these practices. Since P replenishment is fertilizer dependent, greater attention is required in enhancing the accessibility of P fertilizers to smallholder farmers.

Saito K., Diack S., Dieng I., N’Diaye M.K.

Nutrient Manager for Rice (NMR) was tested in the Senegal River valley for the three seasons.NMR is a cloud-based decision-support tool for field-specific fertilizer recommendations.NMR increased rice yield by 1-2.3t/ha compared to farmers' fertilizer practice (FFP).NMR increased profitability by US$ 216-640 per ha compared to FFP. We evaluated recommendations provided by a cloud-based decision-support tool named Nutrient Manager for Rice (NMR) in terms of yield of irrigated lowland rice and profitability in comparison with farmers' fertilizer management practices (FFP) in the Senegal River valley. A total of 102 on-farm trials were conducted over the three seasons (2011 wet season, and 2012 and 2013 dry seasons). On average in each season, NMR recommendations increased rice yield by 1-2.3t/ha and profitability by US$ 216-640 per ha compared to FFP. Differences between FFP and NMR performance were mainly related to timing of the top-dressing of N fertilizer (delayed in the case of FFP), the number of N fertilizer applications (generally just one top-dressing for FFP; two or three for NMR), and application of K. We conclude that NMR offers a promising avenue for increasing the productivity and profitability of irrigated lowland rice in the Senegal River valley.

Saito K., Dieng I., Toure A.A., Somado E.A., Wopereis M.C.

In Africa, there have been scattered reports of yield stagnation. This study examined trends in rice yields in 24 African countries based on United States Department of Agriculture (USDA) data from 1960 to 2012 using segmented linear regression, and determined factors affecting variation in yield growth rates across countries. About 74% of rice harvested area in Africa recently witnessed positive rice yield growth rates of greater than 35 kg ha−1 year−1. Lifting rice yields requires continued investment in rice research on technology development, development or rehabilitation of irrigation schemes, and upgrading of the existing rainfed lowlands to irrigated or partially irrigated systems. Priority should be given to countries with high rice consumption levels, where the investments will be more effective.

Zhang Z., Xie D., Teng W., Gu F., Zhang R., Cheng K., Liu Z., Zhao Y., Yang F.

Cheekilote N., Samant P.K., Dwibedi S.K., Jena B., Mohapatra K.K., Nayak H.S., Garnaik S.

Hartina, Monkham T., Vityakon P., Sukitprapanon T.

This study investigated the effects of humic acid (HA), flue gas desulfurization gypsum (FG), and their combined application on soil chemical properties, rice yield, phosphorus use efficiency (PUE), and phosphorus agronomic efficiency (PAE) during rice production in acidic paddy soil, which has not been previously studied. A greenhouse experiment was conducted in a completely randomized block design with four treatments, including a control (no soil amendments), HA (975 kg ha−1), FG (636 kg ha−1), and HA plus FG. HA application increased the soil pH; cation exchange capacity (CEC); total concentrations of P, Ca, and S; and exchangeable Ca and S. Additionally, HA application maximized the rice yield, total P uptake, PUE, and PAE. FG application alone increased the soil total Ca, whereas coapplication of HA and FG increased the total organic carbon (TOC), CEC, available P, exchangeable Ca, exchangeable S, and total S. However, FG application, both alone and combined with HA, failed to increase the rice yield, PUE, and PAE owing to lower total P uptake by the plants. Therefore, HA application alone is a sustainable soil management practice for acidic paddy soils, whereas FG application must be carefully considered, as it produces disappointing agronomic effects.

Ma H., Zhang H., Gao Q., Li S., Yu Y., Ma J., Zheng C., Cui M., Wu Z., Zhang H.

Intercropping has the potential to improve phosphorus (P) uptake and crop growth, but the potential benefits and relative contributions of root morphology and arbuscular mycorrhizal fungi (AMF) colonization are largely unknown for the intercropping of rice and soybean under dry cultivation. Both field and pot experiments were conducted with dry-cultivated rice (Oryza sativa L.) and soybean (Glycine max L. Merr.) grown alone or intercropped under two P levels. Two root separation modes between rice and soybean were employed to explore the contribution of AMF association and root plasticity on P uptake in intercrops. The results showed that rice/soybean intercropping resulted in a notable increase in the total biomass and yield compared to monoculture in the field. In the potted experiment, compared to the plastic root separation treatment (PS), the no root separation treatment (NS) increased the total biomass and P uptake by 9.4% and 19.9%, irrespective of the P levels. This was primarily attributable to a considerable enhancement in biomass and phosphorus uptake in soybean by 40.4% and 49.7%, which offset a slight decline in the rice of NS compared to PS by 26.8% and 18.0%, respectively. The results of random forest analysis indicate that the P uptake by the dominant species, soybean, was mainly contributed by root morphology, while rice was more dependent on AMF colonization in the intercropping system. Therefore, dry-cultivated rice/soybean intercropping enhances P uptake and productivity by leveraging complementary belowground strategies, with soybean benefiting primarily from root morphological adjustments and rice relying more on arbuscular mycorrhizal fungi colonization.

James M., Tyagi W., Magudeeswari P., Neeraja C.N., Rai M.

Rice provides poor yields in acidic soils due to several nutrient deficiencies and metal toxicities. The low availability of phosphorus (P) in acidic soils offers a natural condition for screening genotypes for grain yield and phosphorus utilization efficiency (PUE). The objective of this study was to phenotype a subset of indica rice accessions from 3000 Rice Genome Project (3K-RGP) under acidic soils and find associated genes and alleles. A panel of 234 genotypes, along with checks, were grown under low-input acidic soils for two consecutive seasons, followed by a low-P-based hydroponic screening experiment. The heritability of the agro-morphological traits was high across seasons, and Ward’s clustering method identified 46 genotypes that can be used as low-P-tolerant donors in acidic soil conditions. Genotypes ARC10145, RPA5929, and K1559-4, with a higher grain yield than checks, were identified. Over 29 million SNPs were retrieved from the Rice SNP-Seek database, and after quality control, they were utilized for a genome-wide association study (GWAS) with seventeen traits. Ten quantitative trait nucleotides (QTNs) for three yield traits and five QTNs for PUE were identified. A set of 34 candidate genes for yield-related traits was also identified. An association study using this indica panel for an already reported 1.84 Mbp region on chromosome 2 identified genes Os02g09840 and Os02g08420 for yield and PUE, respectively. A haplotype analysis for the candidate genes identified favorable allelic combinations. Donors carrying the superior haplotypic combinations for the identified genes could be exploited in future breeding programs.

Bian T., Wang Z., Wang S., Shan X., Wang T., Fu H., Sun Z.

Phosphorus (P) enrichment frequently occurs in the soil used in greenhouse vegetable production (GVP). Minimizing the application of P fertilizer represents a crucial approach to mitigating the accumulation of P in the soil and enhancing its utilization efficiency. However, the changes in bacterial communities and the turnover mechanism of soil P fractions related to soil P cycling after P fertilizer reduction are still unclear. To unravel these complexities, we devised three experimental treatments: conventional nitrogen (N), P, and potassium (K) fertilizer (N1P1K1); conventional N and K fertilizer without P (N1P0K1); and no fertilizer (N0P0K0). These experiments were conducted to elucidate the effects of P reduction on cucumber plant growth, soil P fractions, and the phoD-harboring bacterial community in the P-rich greenhouse soil. The results showed that there were no significant differences between the N1P1K1 and N1P0K1 treatments in terms of plant growth, yield, and P uptake, and the values for the N0P0K0 treatment were significantly lower than those for the N1P1K1 treatment. In a state of P depletion (N0P0K0, N1P0K1), the main P sources were Resin-Pi, NaHCO3-Pi, NaHCO3-Po, and NaOH-Pi. The contents of NaOH-Po and CHCl-Po in the N1P0K1 treatment increased significantly. Without P fertilizer, alkaline phosphatase (ALP) activity, phoD gene abundance, and bacterial community diversity were significantly increased. The abundance of Ensifer in the N0P0K0 and N1P0K1 treatments was 8 and 10.58 times that in the N1P1K1 treatment, respectively. Additionally, total phosphorus (TP) and available nitrogen (AN) were key factors affecting changes in the phoD bacterial community, while Shinella, Ensifer and Bradyrhizobium were the main factors driving the change in soil P fractions, and NaHCO3-Pi and NaOH-Pi were key factors affecting crop yield. Therefore, reducing the application of P fertilizer will increases the diversity of phoD-gene-harboring bacterial communities and promote organic P mineralization, thus maintaining the optimal crop yield.

Kondo K., Hori K., Rakotondramanana M., Ranaivo H.N., Ueda Y., Wissuwa M.

AbstractQTL analysis of heading date (Hd) was performed using a recombinant inbred line population derived from a cross between rice cultivars ʻIR64’ and ʻDJ123’. Phenotypic data was obtained from sites in Japan and Madagascar differing in photoperiod and soil fertility. The Japan site had long-days (LD) and high fertility, while the Madagascar site had short-days (SD) and low fertility conditions. Under LD in Japan, we discovered two Hd QTL on chromosome 7,qHd7.1andqHd7.2, whereas only one of these (qHd7.1) was detected under SD conditions in Madagascar. RILs carrying DJ123 alleles at both QTLs headed 9.5 days earlier in Japan (LD) compared to IR64 alleles, whereas the effect of DJ123 alleles atqHd7.1under SD conditions of Madagascar was 4 days and a combined effect ofqHd7.1andqHd7.2did not exist. In Madagascar, early heading did not carry a yield penalty, whereas it caused reduced grain yield in Japan. These results suggest that RILs harboring the DJ123 allele ofqHd7.1have high yield potential and good adaptation to low fertility conditions in Madagascar and that this can be achieved in a shortened cultivation period, improving resilience to effects of climate change for African rice farmers.

Liu H., Li C., Zhang J., Ji H., Liao Y., Ma X., Li Q., Zhang Y., Jiang L., Wang R., Han X., Jiang Y.

Nitrogen (N) addition can greatly influence soil inorganic phosphorus (Pi) and organic phosphorus (Po) transformations. However, whether and how the N compound forms may differentially affect the soil P fractions remain unclear. Here, we investigated the responses of soil Pi (labile Pi, moderately-occluded Pi, and recalcitrant Pi) and Po fractions (labile Po and stable Po) to varying addition rates of three N compounds ((NH

Ueda Y., Kondo K., Saito H., Pariasca-Tanaka J., Takanashi H., Ranaivo H.N., Rakotondramanana M., Wissuwa M.

The rice panicle is the principal organ to influence productivity and traits affecting panicle architecture determine sink size and yield potential. Improving panicle architecture may be effective in increasing yield under low-input conditions, but which traits are of importance under such conditions and how they are genetically controlled is not well understood. Using recombinant inbred lines (RILs) derived from a cross between a modern variety IR64 and a low fertility tolerant accession DJ123, quantitative trait locus (QTL) mapping was conducted under high soil fertility in Japan and low fertility in Madagascar. Among QTL for panicle length (PL) detected, the DJ123 allele increased rachis length at qCL1 and qPL9, while the IR64 allele increased primary branch length at qPL7. DJ123 further contributed two QTL for grain width whereas IR64 contributed two grain length QTL. Analysis of lines carrying different combinations of detected QTL indicates that rachis and primary branch lengths are independently regulated, explaining strong transgressive segregation for PL. The positive effects of PL-related QTL were further confirmed by a genome-wide analysis of allelic states in two breeding lines that had been selected repeatedly for total panicle weight per plant under low input conditions. This study provides the genetic basis for complex panicle architecture in rice and will aid in designing an ideal panicle architecture that leads to increased yield under low fertility conditions.

Oo A.Z., Tsujimoto Y., Mukai M., Nishigaki T., Takai T., Uga Y.

Phosphorus (P) deficiency is a major limiting factor for rice production in the tropics. The root system architecture (RSA) may play a significant role to capture P efficiently in soils; however, its function is poorly understood in flooded and puddled soil cultures. Two near-isogenic lines (NILs) contrasting RSA—qsor1-NIL (nonfunctional allele of qSOR1; shallow RSA) and Dro1-NIL (functional allele of DRO1; deep RSA)—were repeatedly grown for approximately 6 weeks in pots with three stratified P treatments. The treatments simulated P deficient conditions in puddled and subsoil layers, P available in the puddled layer, and P available in puddled and subsoil layers, that is, −P−P: no P applied in either the top-half (0–14 cm) or bottom-half (14–28 cm) layers; +P−P: P applied only in the top-half layer; and +P + P: P applied in the top-half and bottom-half layers, respectively. A significant interaction was observed between genotype and P treatment. The Dro1-NIL had a greater root surface area in the bottom half layer, which was advantageous for capturing P in the subsoil layer and resulted in greater biomass and P uptake in the +P + P treatment. Contrarily, the qsor1-NIL had a greater root surface area and longer root hair, resulting in greater biomass and P uptake in the −P−P treatment. The mechanism is unclear; however, the pleiotropic effect of qsor1, namely enhancing root hair elongation, might be more advantageous to explore P with minimal carbon costs than elongating nodal and lateral roots when P is not available in deep soil layers. No genotype differences were observed in the +P−P treatment, implying no apparent topsoil P-foraging effect of the shallow RSA in the flooded soil culture. The roles of RSA and root hairs should attract further attention for the genotypic improvement of lowland rice under P deficiency conditions in the tropics.

Liu C., Wang J., Wang Y., Li L., Feng Z., Xian Y., Jiang Y., Yu J., Tong T., Li X., Yao M.

In agriculture, cropping and fertilization practices can significantly affect the soil microbial community, which in turn affects crop growth. Nevertheless, it remains uncertain how cropping and fertilization treatments influence the structure, function, and metabolic characteristics of microbial communities from bulk soil to rhizosphere soil. Here, a dual-factor experiment was carried out in the black soil of Northeast China, involving cropping (soybean—maize rotation and continuous maize cultivation) and fertilization (no fertilizer control, chemical fertilizer, and chemical fertilizer plus straw incorporation) treatments. After 10 years of experimentation, we collected the maize non-rhizosphere and rhizosphere soil and maize root samples, and conducted the quantification and amplicon sequencing of the 16S rRNA gene and ITS region, as well as metagenomic sequencing and metabolome analysis of soil samples. Our results revealed that fertilization exerts a greater influence than cropping practices on microbial community structures from soil to maize root by largely altering soil chemical properties, and on various metabolic genes and pathways. Crop rotation primarily mediated microbial community assembly by influencing specific functional groups. Compared to continuous cropping, crop rotation enriches beneficial bacteria, fungi and mycovirus, suppresses fungal pathogen abundance, and lowers fungal species diversity in the maize rhizosphere through balancing metabolites originating from a variety of plant and microbial sources. Crop rotation also imposes stronger homogeneous selections on the prokaryotic community than continuous cropping. In summary, cropping and fertilization treatments shape the maize root-microbiome relationships with distinct mechanisms.

Wang H., Nabi F., Sajid S., Kama R., Shah S.M., Wang X.

The crop straw returning to the field is a widely accepted method to utilize and remediate huge agricultural waste in a short period. However, the low temperatures and dry conditions of the winter season in Southwest China can be challenging for the biodegradation of crop straw in the field. With a similar aim, we designed a short-term study where rice straw was applied to the field with different concentrations of nitrogen (N) fertilizer while keeping phosphorus (P) constant; CK, (N0P0); T1, (N0P90); T2, (N60P90); T3, (N120P90); and T4, (N180P90) were added to evaluate its impact on straw degradation during cold weather. We found that high fertilization (T4) significantly improved crop yield, organic matter, and lignocellulose degradation under cold temperatures (21.5–3.2 °C). It also significantly improved soil nitrogen agronomic efficiency, nitrogen use efficiency, and nitrogen physiological efficiency. The yield was highest in T4 (1690 and 1399 kg/ha), while T3 acted positively on soil lignocellulolytic enzyme activity, which in turn resulted in higher degradation of OM and lignocellulosic material. Pearson’s correlation analysis revealed that total nitrogen, total phosphorus, available nitrogen, and available phosphorus were important variables that had a significant impact on soil EC, bulk density, water holding capacity, and soil enzymes. We found that nitrogen application significantly changed the soil bacterial community by increasing the richness and evenness of lignocellulolytic bacteria, which aided the degradation of straw in a short duration. This study’s finding indicates that the decomposition of crop straw in the field under cold weather stress was dependent on nutrient input, and N, in an appropriate amount (N120-180), was suitable to achieve higher yield and higher decomposition of straw in such an environment.

Sar P., Aiswarya V.S., Basha F.T., Deo R., Verma B.C., Bhaduri D., Chakraborty K., Ngangkham U., Banerjee A., Kumar J., Mandal N.P., Roy S.

AbstractThe limited availability of Phosphorus (P) in the soil poses a significant challenge to of rice productivity in rainfed tropical regions. There has been a constant demand of diverse donors for enhancing tolerance to P‐deficient soils. In this study, we evaluated 181 aus rice accessions of the 3000 Rice Genome Project (3 K‐RGP) for grain yield and six other agronomical traits under control (~20 mg kg−1 available P) and low‐P (8–10 mg kg−1 available P) field trials. The objectives were to assess the level of low‐P tolerance in the aus germplasm and select stable high‐yielding accessions using stress tolerance attributes. We also surveyed the presence of PSTOL1 gene and Pup1 polymorphisms to find the effect of PSTOL1 as well as t Pup1 haplotypes on low‐P tolerance. Principal component analysis (PCA) using five stress tolerance attributes revealed that attributes like mean productivity (MP) and stress tolerance index (STI) are useful for selecting high‐yielding accessions with stable yield under stress and control conditions. Notably, accessions like Kalabokari, Devarasi, ARC 12021, Jasure Aus, ARC 7336 and ARC 12101 had higher level of tolerance than the check varieties Vandana and Sahbhagi Dhan. Majority of aus accessions carried the PSTOL1 gene (73%) and had the tolerant haplotype of Pup1 (65%) like the tolerant checks. Although, at large, the PSTOL1‐positive accessions were more vigorous, and high yielding under low‐P, there were a few PSTOL1‐negative aus accessions showing higher level of tolerance. The findings suggest that non‐PSTOL1 type tolerance exists in aus rice which needs to be substantiated through further studies.

Mundschenk E., Remus R., Augustin J., Wissuwa M., Staudinger C., Oburger E., George E., Holz M.

Abstract Aims High Phosphorus (P) efficiencies such as internal P utilization efficiency (PUE) and P acquisition efficiency (PAE) are crucial for upland rice production, particularly on highly P-fixing soils like Andosols. While the effect of root traits associated with high PAE in upland rice has been studied intensively, less attention has been given to the origin of P (native soil-P versus fertilizer-P) taken up by plants when evaluating differences in P efficiency. Here we aim to evaluate the efficiency of different upland rice genotypes to acquire native soil-P and fertilizer-P. Methods Four upland rice genotypes with varying PAE were grown in an Andosol at low- and high-P fertilization level and harvested 9 and 34 days after emergence. Fertilizer-P was labeled with 33P to distinguish between the efficiency to acquire P originating from native soil and fertilizer by measuring plant P uptake. Results Increased fertilizer supply enhanced native soil-P uptake. Under low-P conditions the genotype DJ123 showed a superior PAE and an increased acquisition of native soil-P while AB199 was identified to have a superior internal PUE under P deficient conditions. Differences between genotypes in overall PAE under high-P conditions were not significant but the distinction of P sources showed that genotype DJ123 acquired significantly more native soil-P per unit root than all other genotypes. Conclusions Our results indicate that variations in PAE among genotypes are associated with their ability to access native soil-P. DJ123 emerged as the most adept genotype in acquiring sparingly soluble native soil-P and future studies should unravel the rhizosphere processes underlying increased PAE of native soil-P.

Meng Q., Fan W., Liu F., Wang G., Di X.

Soil cadmium (Cd) contamination poses a serious threat to ecosystems, and the application of phosphorus fertilizers can reduce Cd toxicity. However, the specific effects of different phosphorus fertilizers on the subcellular distribution and chemical morphology of Cd in eggplant grown in calcareous Cd-contaminated soil remain unclear. This study examined the impact of various types and levels of phosphate fertilizers on the subcellular distribution and chemical morphology of cadmium in eggplant seedlings using a two-factor analysis. The investigation was conducted via a pot experiment utilizing a two-factor analysis. The application of 0.35 g kg−1 dicalcium phosphate significantly decreased the Cd content in the subcellular distribution and induced notable alterations in the chemical morphology of Cd in eggplant roots. Specifically, the ethanol-extracted Cd state decreased by 65.45%, and the sodium chloride-extracted Cd state decreased by 64.65%. Conversely, Cd extracted by deionized water, acetic acid, hydrochloric acid, and the residue state increased by 6.20%, 4.01%, 20.87%, and 17.85%, respectively. The application of 0.35 g kg−1 dicalcium phosphate resulted in the most significant reduction in Cd content in eggplant and modification of subcellular Cd distribution and chemical morphology in roots.