Effectiveness of combined application of Kodjari phosphate rock,water soluble phosphorus fertilizer and manure in a Ferric Lixisol in the centre west of Burkina Faso

Increasing soil phosphorus and organic matter content for crop production while reducing the cost of production are required to facilitate the achievement of green revolution in Africa. Field and pot experiments were laid out during 2012 and 2013 to assess the effects of combined application of Kodjari phosphate rock (PR) and water soluble phosphorus on sorghum yields, P uptake and Lixisol characteristics in the centre west of Burkina Faso. Five P fertilizers treatments (zero P, 100% TSP (triple super phosphate), 100% PR, 50% PR + 50% TSP, 75% PR + 25% TSP) and two cow manure treatments (zero, 5 t ha^?1) were tested. In field experiment, 50% PR + 50% TSP was as effective as 100% TSP in increasing sorghum yield above the control by 30% in 2012 and 50% in 2013 and P uptake by 30% in both years. Manure had an additive effect on phosphorus fertilizers in increasing sorghum yields and P uptake. In pot experiment, increases of Ca uptake, soil pH and microbial P were observed with the application of 50% PR + 50% TSP. Our results suggest that formulation of fertilizer combining phosphate rock and mineral P would improve sorghum yields and income of smallholders.     

Organic resources and earthworms affect phosphorus availability to sorghum after phosphate rock addition in semi-arid West Africa

A field experiment was laid out in Burkina Faso (West Africa) on an Eutric Cambisol to investigate the interaction of organic resource quality and phosphate rock on crop yield and to assess the contribution of earthworms (Millsonia inermis Michaelsen) to P availability after phosphate rock application. Organic resources of different quality were applied at a dose equivalent to 40 kg N ha^–1 with or without phosphate rock from Kodjari (Burkina Faso) at a dose equivalent to 25 kg P ha^–1, and were compared with control and single phosphate rock treatments in a factorial complete block design with four replicates. Sorghum (Sorghum bicolor L. Moench) variety SARIASSO 14 was grown. Sheep dung had the highest impact on earthworm casting intensity followed by maize straw. Combining organic resources with phosphate rock reduced earthworm casting activities compared to a single application of organic resources or phosphate rock. Addition of phosphate rock to maize straw reduced P availability in earthworm casts whereas combining sheep dung or compost with phosphate rock increased P availability. The contribution of earthworms to Kodjari phosphate rock solubilisation mainly occurred through their casts, as the available P content of casts was 4 times higher than that of the surrounding soil.     

Comparative Effects of Two Forage Species on Rhizosphere Acidification and Solubilization of Phosphate Rocks of Different Reactivity

ABSTRACT

Dissolution of phosphate rocks (PR) in soils requires an adequate supply of acid (H⁺) and the removal of the dissolved products [calcium (Ca^{2 +}) and dihydrogen phosphate (H₂PO₄ ^?)]. Plant roots may excrete H⁺ or OH^? in quantities that are stoichiometrically equal to excess cation or anion uptake in order to maintain internal electroneutrality. Extrusion of H⁺ or OH^? may affect rhizosphere pH and PR dissolution. Differences in rhizosphere acidity and solubilization of three PRs were compared with triple superphosphate between a grass (Brachiaria decumbens) and a legume (Stylosanthes guianensis) forage species at two pH levels (4.9 and 5.8) in a phosphorus (P)-deficient Ultisol with low Ca content. The experiment was performed in a growth chamber with pots designed to isolate rhizosphere and non-rhizosphere soil. Assessment of P solubility with chemical extractants led to ranking the PRs investigated as either low (Monte Fresco) or high solubility (Riecito and North Carolina). Solubilization of the PRs was influenced by both forage species and mineral composition of the PR. The low solubility PR had a higher content of calcite than the high solubility PRs, which led to increased soil pH values (> 7.0) and exchangeable Ca, and relatively little change in bicarbonate-extractable soil P. Rhizosphere soil pH decreased under Stylosanthes but increased under Brachiaria. The greater ability of Stylosanthes to acidify rhizosphere soil and solubilize PR relative to Brachiaria is attributed to differences between species in net ion uptake. Stylosanthes had an excess cation uptake, defined by a large Ca uptake and its dependence on N₂ fixation, which induced a significant H⁺ extrusion from roots to maintain cell electroneutrality. Brachiaria had an excess of anion uptake, with nitrate (NO₃ ^?) comprising 92% of total anion uptake. Nitrate and sulfate (SO₄ ^{2 ?}) reduction in Brachiaria root cells may have generated a significant amount of cytoplasmic hydroxide (OH^?), which could have increased cytoplasmic pH and induced synthesis of organic acids and OH^? extrusion from roots.     

Combined effect of deficit irrigation and potassium fertilizer on physiological response,plant water status and yield of soybean in calcareous soil

A 2-year field experiment (2013 and 2014) was conducted in calcareous soil (CaCO₃ 19.2%), on soybean grown under three irrigation regimes 100%, 85% and 70% of crop evapotranspiration combined with three potassium (K₂O) levels (90, 120 and 150 kg ha^?1). The objective was to investigate the complementary properties of potassium fertilizer in improving soybean physiological response under water deficit. Plant water status (relative water content RWC, chlorophyll fluorescence F_v/F₀ and F_v/F_m), had been significantly affected by irrigation or/and potassium application. Potassium improved growth characteristics (i.e. shoot length, number, leaf area and dry weight of leaves) as well as physiochemical attributes (total soluble sugars, free proline and contents of N, P, K, Ca and Na). Yield and yield water use efficiency (Y-WUE) were significantly affected by irrigation and potassium treatments. Results indicated that potassium application of 150 and 120 kg ha^?1 significantly increased seed yield by 29.6% and 13.89%, respectively, compared with 90 kg ha^?1 as average for two seasons. It was concluded that application of higher levels of potassium fertilizer in arid environment improves plant water status as well as growth and yield of soybean under water stress.     

Ameliorative Effects of Potassium Phosphate on Salt‐Stressed Pepper and Cucumber

Abstract

Bell pepper (Capsicum annuum cv. Urfa Isoto) and cucumber (Cucumis sativus cv. Beith Alpha F1) were grown in pots containing field soil to investigate the effects of supplementary potassium phosphate applied to the root zone of salt‐stressed plants. Treatments were (1) control: soil alone (C); (2) salt treatment: C plus 3.5 g NaCl kg^?1 soil (C + S); and (3) supplementary potassium phosphate: C + S plus supplementary 136 or 272 mg KH₂PO₄ kg^?1 soil (C + S + KP). Plants grown in saline treatment produced less dry matter, fruit yield, and chlorophyll than those in the control. Supplementary 136 or 272 mg KH₂PO₄ kg^?1 soil resulted in increases in dry matter, fruit yield, and chlorophyll concentrations compared to salt‐stressed (C + S) treatment. Membrane permeability in leaf cells (as assessed by electrolyte leakage from leaves) was impaired by NaCl application. Supplementary KH₂PO₄ reduced electrolyte leakage especially at the higher rate. Sodium (Na) concentration in plant tissues increased in leaves and roots in the NaCl treatment. Concentrations of potassium (K) and Phosphorus (P) in leaves were lowered in salt treatment and almost fully restored by supplementary KH₂PO₄ at 272 mg kg^?1 soil. These results clearly show that supplementary KH₂PO₄ can partly mitigate the adverse effects of high salinity on both fruit yield and whole plant biomass in pepper and cucumber plants.     

Evaluation of fertilizers solubility and phosphate release in slightly acidic arable soil

The geochemical reactivity of single superphosphate (SSP), triple superphosphate (TSP), phosphate rock (PR), partially acidulated phosphate rock (PAPR) and potassium dihydrogen phosphate (KH₂PO₄) was evaluated in an incubation trial. The soil was Anthrosols, Ap horizon (Sandy loam). Solubility equilibrium of phosphates was calculated by phosphate (P_Pot = logH₂PO₄ – pH) and calcium (Ca_Pot = logCa + 2pH) potentials. Next, activity ratio (AR°) and Woodruff potential (ΔF) were considered for estimating phosphate dynamics in the soil. Data showed that phosphate potentials stressed on significant solubility process and varied accordingly to the rates of the fertilizers: ?5.50, ?4.81, ?4.47 and ?4.09 for 0, 50, 100 and 150 kg P ha^?1. The values of the Woodruff potential (ΔF) varied widely from ?1929 to 8573 cal mol^?1, i.e., from marginal supplying power in the case of the control treatment to very high supplying power for the TSP (Triple superphosphate). These findings are of practical value for the following reasons: TSP and KH₂PO₄ are recommended for quick and high P supply to plants; SSP and PAPR for moderate supply and finally PR for slow and low supply. Phosphorus efficiency should be treated with priority particularly for areas with intensive cropping and susceptibility to runoffs.     

Factors Influencing the Dissolution of Phosphate Rock in a Range of High P‐Fixing Soils from Cameroon

Abstract

A laboratory incubation experiment was conducted to evaluate the soil factors that influence the dissolution of two phosphate rocks (PRs) of different reactivity (Gafsa, GPR, reactive PR; and Togo‐Hahotoe, HPR, low reactivity PR) in seven agricultural soils from Cameroon having variable phosphorus (P)‐sorption capacities, organic carbon (C) contents, and exchangeable acidities. Ground PR was mixed with the soils at a rate of 500 mg P kg^?1 soil and incubated at 30°C for 85 days. Dissolution of the PRs was determined at various intervals using the ΔNaOH‐P method (the difference of the amount of P extracted by 0.5 M NaOH between the PR‐treated soils and the control). Between 4 and 27% of HPR and 33 and 50% of GPR were dissolved in the soils. Calcium (Ca) saturation of cation exchange sites and proton supply strongly affected PR dissolution in these soils. Acid soils with pH‐(H₂O)<5 (NKL, ODJ, NSM, MTF) dissolved more phosphate rock than those with pH‐(H₂O)>5 (DSC, FGT, BAF). However, the lack of a sufficient Ca sink in the former constrained the dissolution of both PRs. The dissolution of GPR in the slightly acidic soils was limited by increase in Ca saturation and that of HPR was constrained by limited supply in protons. Generally, the dissolution of GPR was higher than that of HPR for each soil. The kinetics of dissolution of PR in the soils was best described by the power function equation P=At^B. More efficient use of PR in these soils can be achieved by raising the soil cation exchange capacity, thereby increasing the Ca sink size. This could be done by amending such soils with organic materials.     

Metal contents of phosphate rocks

Abstract

Significant amounts of phosphate rocks (PRs) are mined around the world annually. The rocks are either applied directly to soils or manufactured to produce water‐soluble phosphorus (P) fertilizers. In this study, we analyzed 12 PRs obtained from various deposits in Africa, United States, and Peru for total P, ten trace metals [cadmium (Cd), cobalt (Co), copper (Cu), chromium (Cr), lithium (Li), manganese (Mn), nickel (Ni), lead (Pb), rubidium (Rb), and zinc (Zn)] and eight nontrace metals [aluminum (Al), barium (Ba), calcium (Ca), iron (Fe), potassium (K), magnesium (Mg), sodium (Na), and strontium (Sr)]. The empirical formulae and the unit‐cell a dimension of the apatite contents were also determined. Results showed that the values of the unit‐cell a dimension ranged from 9.324 Å for North Carolina PR to 9.365 Å for Tahoua PR. The total P contents ranged from 109 g/kg for Kodjari PR to 176 g/kg for Parc W PR. The concentration of the trace metals in the PRs varied considerably. Expressed in mg/kg PR, the ranges and median values were: Cd (5–47, 10), Co (6–104, 22), Cu (5–41, 8), Cr (18–331, 46), Li (2–9, 2), Mn (11–6553, 263) , Ni (1–61, 10) , Pb (7–43, 14), Rb (3–18, 6), and Zn (54–576, 124). The corresponding values of the nontrace metals expressed in g/kg were: Al (1.7–20.0, 5.6), Ba (0–4.4, 0.4), Ca (211–330, 298), Fe (1.4–45.7, 6.8), K (0.3–10.9, 1.4), Mg (0.6–16.9, 2.2), Na (1.0‐ 22 .8, 10.4), and Sr (0.3–6.7, 1.0). At the detection limit of 5 ng/mL, no cesium (Cs) was found in the PR analyzed.     

Silicon fertilization – A tool to boost up drought tolerance in wheat (Triticum aestivum L.) crop for better yield

In this study, impact of silicon (Si) application on wheat performance under drought stress is studied. Experimental soil was sandy clay loam with an average pH of 8.01, electrical conductivity (EC) of 2.36 dSm^?1, and calcium carbonate (CaCO₃) content of 2.16%. Soil was severely deficient in organic matter (<1%). Average extractable phosphorus (P) and potassium (K) concentration was 230 and 5.21 mg kg^?1, respectively. Silicon potassium metasilicate (K₂SiO₃) was applied at the rate of 0 and 12 kg/ha with three canal water irrigation frequencies including two, three, and four under randomized complete block design (RCBD) factorial fashion with three replications. Results indicated that drought stress significantly reduced plant height, spike length, shoot fresh weight, and number of spikelets/spike, eventually enhancing wheat yield. Concentration of K⁺ in shoot (28.65 mg g^?1) and grains (3.51 mg g^?1) increased with Si application, which helped to maintain water potential in plant even under reduced moisture level in plants and soil, ultimately producing more yield and biomass under drought stress conditions.     

Vermicomposting leachate as liquid fertilizer for the cultivation of sugarcane (Saccharum sp.)

In vermicomposting, the main product is the worm casts, but a leachate is generated that contains large amounts of plant nutrients. This leachate is normally diluted to avoid plant damage. We investigated how dilution of vermicompost leachate combined with different concentrations of nitrogen (N) - phosphorus (P) - potassium (K) triple 17 fertilizer, and polyoxyethylene tridecyl alcohol as dispersant and polyethylene nonylphenol as adherent to increase efficiency of fertilizer uptake, affected sugarcane plant development. The vermicomposting leachate with pH 7.8 and electrolytic conductivity 2.6 dS m^?1, contained 834 mg potassium (K) l^?1, 247 mg nitrate (NO₃^?) l^?1 and 168 mg phosphate (PO₄^3?) l^?1, was free of pathogens and resulted in a 65% germination index. Vermicompost leachate did not inhibit sugarcane growth and mixed with 170 g l^?1 NPK triple 17 fertilizer resulted in the best plant development. No dispersant or adherent was required to improve plant height and stem development.     

Symbiotic parameters,growth, nutrient accumulation,productivity and profitability as influenced by integrated nutrient management in lentil (Lens culinaris)

Field experiments evaluated the effects of integrated nutrient management on symbiotic parameters, growth, nutrient accumulation, productivity and profitability of lentil (Lens culinaris Medikus). Application of recommended dose of nutrients (RDN, 12.5 kg N ha^?1 + 40 kg P₂O₅ ha^?1) + 25 kg ZnSO₄ ha^?1 + seed inoculation with biofertilizers [Rhizobium + phosphate solubilizing bacteria (PSB) + plant growth promoting rhizobacteria (PGPR)] + 1.0 g ammonium molybdate kg^?1 seed recorded the highest number & dry weight of nodules, leghaemoglobin content, root & shoot dry weight, plant height, number of pods plant^?1 and 100-seed weight. The next best treatment was RDN + seed inoculation with biofertilizers + 1.0 g ammonium molybdate kg^?1 seed. On the basis of mean of three-year data, the treatment of RDN + 25 kg ZnSO₄ ha^?1 + seed inoculation with biofertilizers + 1.0 g ammonium molybdate kg^?1 seed proved the best in realizing the highest grain yield (34.0%), gross returns (34.0%) and net returns (54.8% higher over control). Nitrogen, phosphorus and potassium in the grains and straw were significantly improved where RDN was applied in combination with seed inoculation, basal application of ZnSO₄ and seed treatment with 1 g ammonium molybdate than their single applications.     

Organic Lettuce Growth And Nutrient Uptake Response To Lime,Compost And Rock Phosphate

Fertilizer recommendations are needed to increase organic vegetable yields. Thus, organic lettuce growth and nutrient uptake was investigated in a randomized block pot experiment with twelve treatments from the factorial structure of three factors: (i) Gafsa phosphate [0 and 200 kg phosphorus pentoxide (P₂O₅) ha^?1], (ii) compost from source separated municipal organic waste (0, 15, and 30 t ha^?1) and (iii) limestone [0 and 8 t ha^?1 calcium carbonate (CaCO₃) equivalent]. Lettuce yield increased with compost application and a first order interaction between lime and phosphate was clear because lime partially replaced the need for phosphate. This was explained by the effect of liming on P availability in acid soils. Nitrogen (N), phosphorus (P), and potassium (K) accumulation increased in lettuces produced with compost or phosphate but only the accumulation of N was increased with lime. This compost is recommended to increase nutrient availability for organic lettuce whereas the need for phosphate fertilization may decrease with liming.     

Effect of Five Phosphate Rocks on Red Clover (Trifolium pratense L.) Yield in Pot Trial

Abstract

Phosphorus (P) availability in five phosphate rocks with different P solubility was compared with that in single superphosphate and superphosphate+lime in a pot experiment with red clover as test plant on a Lamellic Arenosol with sand soil texture and on a Haplic Luvisol with clay loam soil texture, both strongly acid with low P supply. Phosphorus rates in the pot experiment were 0, 100, 400, and 1600 mg total P₂O₅ kg^?1. On both soils, there was a weak correlation between total added P and red clover P responses. If P solubility of the PRs was also taken into account, the correlation between formic acid–, citric acid–, or neutral ammonium citrate–soluble P amounts added and red clover responses became much stronger. Soil P availability was estimated by water, Olsen, Lakanen‐Erviö, and ammonium lactate tests. Among the P extractants studied, Olsen soil P test gave the best correlation with red clover yields.     

Interactive Effect of Fluorescent Pseudomonads Rhizobacteria and Zn on the Growth,Chemical Composition,and Water Relations of Pistachio (Pistacia vera L.) Seedlings under NaCl Stress

The role of fluorescent pseudomonads isolates (pf₀, pf₁, pf₂, and pf₃) and zinc (Zn) (0 and 5 mg kg^?1 soil) interactions in alleviating salinity in pistachio seedlings were investigated. The experiment was conducted following completely randomized design with three replicates. The results revealed that salinity decreased the growth parameters, while application of PGPR (plant growth-promoting rhizobacteria) and Zn increased these parameters. Application of PGPR significantly enhanced phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), Zn, Ca/sodium (Na), and K/Na contents, while decreased the accumulation of Na and chloride (Cl). Application of PGPR and Zn increased the phenolic compounds, sucrose, membrane stability index (MSI), and relative water content (RWC) but reduced the malondialdehyde (MDA) amount. A positive correlation was observed between Zn concentrations with seedling dry weights, phenolic compounds, MSI, and RWC contents. These results indicated that the combined application of PGPR and Zn could be a simple treatment for growth and establishment of pistachio seedlings under Zn deficiency and soil salinity.     

High Sodium in Irrigation Water Caused B Toxicity at Low Soil Solution and Shoot B Concentration in Maize (Zea mays L.)

Sodium (Na) and calcium (Ca) in brackish water differentially affects boron (B) nutrition of plants grown on calcareous and salt-affected soils. A glasshouse experiment was conducted to evaluate the effect of brackish irrigation water with different sodium adsorption ratio (SAR_iw) [distilled-water control, 8, and 16 (mmol_c L^?1)^1/2] on B nutrition of maize. Plants were grown for 40 days with 5 levels of B (0, 1.29, 2.30, 3.22, and 4.46 mg kg^?1 soil). Boron application significantly improved plant growth at lower rates. High B rates and application of high SAR_iw decreased plant growth independently, and the reduction in growth was further aggravated due to combined effect of both B and high SAR_iw. Decreased growth was attributed mainly to increased shoot B and Na concentration, while decreased Ca concentration. These ionic changes also altered internal and external B requirements. Yield decrease was observed at lower B concentration in soil solution B and plants shoot grown with high SAR_iw than in plants grown with distilled water and low B application rates.     

Variable inhibition of iron uptake by oat phytosiderophore in five soybean cultivars

Abstract

Greenhouse experiment was conducted to evaluate the effect of arbuscular mycorrhizal fungi (AMF) on plant growth, and nutrient uptake in saline soils with different salt and phosphorus (P) levels. The following treatments were included in this experiment: (i) Soil A, with salt level of 16.6 dS m^?1 and P level of 8.4 mg kg^?1; (ii) Soil B, with salt level of 6.2 dS m^?1 and P level of 17.5 mg kg^?1; and (iii) Soil C, with salt level of 2.4 dS m^?1 and P level of 6.5 mg kg^?1. Soils received no (control) or 25 mg P kg^?1 soil as triple super phosphate and were either not inoculated (control) or inoculated with a mixture of AM (AM1) and/or with Glomus intraradices (AM2). All pots were amended with 125 mg N kg^?1 soil as ammonium sulfate. Barley (Hordeum vulgar L., cv. “ACSAD 6”) was grown for five weeks. Plants grown on highly saline soils were severely affected where the dry weight was significantly lower than plants growing on moderately and low saline soils. The tiller number and the plant height were also lower under highly saline condition. The reduced plant growth under highly saline soils is mainly attributed to the negative effect of the high osmotic potential of the soil solution of the highly saline soils which tend to reduce the nutrient and water uptake as well as reduce the plant root growth. Both the application of P fertilizers and the soil inoculation with either inoculum mixture or G. intraradices increased the dry weight and the height of the plants but not the tiller number. The positive effect of P application on plant growth was similar to the effect of AM inoculation. Phosphorus concentration in the plants was higher in the mycorrhizal plant compared to the non mycorrhizal ones when P was not added. On the other hand, the addition of P increased the P concentration in the plants of the non mycorrhizal plants to as high as that of the mycorrhizal plants. Iron (Fe) and zinc (Zn) uptake increased with AM inoculation. The addition of P had a positive effect on micronutrient uptake in soil with low level of soil P, but had a negative effect in soil with high level of soil P. Micronutrient uptake decreases with increasing soil salinity level. Inoculation with AMF decreases sodium (Na) concentration in plants grown in soil of the highest salinity level but had no effect when plants were grown in soil with moderate or low salinity level. The potassium (K) concentration was not affected by any treatment while the K/Na ratio was increased by AM inoculation only when plant were grown in soil of the highest salinity level.     

Growth response of the salt-sensitive and the salt-tolerant sugarcane genotypes to potassium nutrition under salt stress

Adequate regulation of mineral nutrients plays a fundamental role in sustaining crop productivity and quality under salt stress. We investigated the ameliorative role of potassium (K as K₂SO₄) in overcoming the detrimental effects of sodium chloride (NaCl) on sugarcane genotypes differing in salt tolerance. Four levels of NaCl (0, 100, 130 and 160 mM) were imposed in triplicate on plants grown in gravel by supplying 0 and 3 mM K. The results revealed that application of NaCl significantly (p ≤ 0.05) increased sodium (Na⁺) but decreased K⁺ concentrations in shoots and roots of both genotypes with a resultant decrease in K⁺/Na⁺ ratios. Physical growth parameters and juice quality were also markedly reduced with increasing NaCl concentrations compared with controls. However, addition of K alleviated the deleterious effects of NaCl and improved plant growth under salt stress. Cane yield and yield attributes of both genotypes were significantly (p ≤ 0.05) higher where K was added. Juice quality was also significantly (p ≤ 0.05) improved with the application of K at various NaCl levels. The results suggested that added K interfered with Na⁺, reduced its uptake and accumulation in plant tissues and consequently improved plant growth and juice quality in sugarcane.     

INFLUENCE OF SODIUM CHLORIDE AND CALCIUM FOLIAR SPRAY ON HYDROPONICALLY GROWN PARSLEY IN NUTRIENT FILM TECHNIQUE SYSTEM

The effects of salinity [30 or 90 mM sodium chloride (NaCl)] and calcium (Ca) foliar application on plant growth were investigated in hydroponically-grown parsley (Petroselinum crispum Mill). Increasing salinity reduced fresh weight and leaf number. Calcium alleviated the negative impacts of 30 mM NaCl on plant biomass and leaf fresh weight but not in case of 90 mM. Plant height, leaf and root dry weight and root length did not differ among treatments. Total phenols increased with calcium application, chlorophyll b reduced by salinity, while total carotenoids increased with salinity and/or Ca application. Salinity reduced nutrient uptake [nitrate (NO₃), potassium (K), phosphorus (P) and Ca] and elemental content in leaves and roots. Calcium application reduced P but increased Ca content in plant tissues. Increments of Na uptake in nutrient solution resulted in higher Na content in leaves and roots regardless Ca application. These findings suggest that calcium treatment may alleviate the negative impacts of salinity.     

Use of Potassium Fertilization to Ameliorate the Adverse Effects of Saline-sodic Stress Condition (ECw: SARw Levels) in Rice (Oryza Sativa L.)

ABSTRACT

Salt-affected soils expand around the world and become a critical handicap for high crop yield. Saline-sodic soil contributed a major portion in salt-affected soils. Such types of soils have a sizable amount of Na⁺ in nutrient medium and that reduce the K⁺ uptake in plants. A hydroponic experiment was performed to investigate the ameliorative effect of different doses of potassium fertilizer (K₁ = 0.3, K₂ = 0.6 and K₃ = 1.2 mM L^?1) on rice (Oryza sativa L.) under different EC_w (6 dS m^?1) and SAR_w [12 and 24 (mmol L^?1)^1/2] levels. Application of K⁺ at elevated levels under saline-sodic conditions improved the concentration of anti-oxidant enzymes, plant physiological, and biochemical attributes by improving the K⁺: Na⁺ ratio in plant tissues. Total phenolic content, total soluble protein, and soluble sugar content of rice plant were increased with an increase in potassium dose and saline-sodicity. Maximum K⁺: Na⁺ ratios, 4.13 and 2.0 were observed in shoot and root, respectively upon application of K⁺ at 1.2 mM L^?1 in a solution having EC_w: SAR_w level of 6: 12. This study suggested that application of potassium at elevated levels (1.2 mM L^?1) has enhanced the rice growth by reducing the harmful effect of Na⁺ salts on plant physiology, biochemical attributes, and anti-oxidant enzymes under specific saline-sodic conditions.     

Enhancement Effect of Water-Soluble Phosphorus on Agronomic Effectiveness of Phosphate Rocks

ABSTRACT

Direct application of phosphate rocks (PRs) with low/medium in reactivity has shown to be low in agronomic effectiveness for cereal crops. Presence of water-soluble P (WSP) in the vicinity of PR can significantly enhance the rooting system at the early stage of plant growth. This, in turn, can enable the plant to utilize the associated PR more effectively than the use of PR alone at planting. This report presents the results of several greenhouse experiments that show the granulated (WSP+PR) products by dry compaction process using different low-reactive PR sources were as effective as WSP fertilizers viz triple superphosphate (TSP) and monoammonium phosphate (MAP). The test plants were maize (30 days) and soybean and upland rice were grown to maturity on acid or neutral soils. Based on the results obtained a P ratio of 50:50 between WSP and PR is recommended for the granulated (WSP+PR) products that can achieve crop yields at the same levels as that with the WSP fertilizers.

Abbreviations: phosphate rock, PR; water-soluble P, WSP; dry-matter yield, DMY