Effect of Salinity and Nitrogen Application on Growth,Chemical Composition and Some Biochemical Indices of Pistachio Seedlings (Pistacia Vera L.)

To study the effect of nitrogen and salinity on growth and chemical composition of pistachio seedlings (cv. ‘Badami’), a greenhouse experiment was conducted. Treatments consisted of four salinity levels [0, 800, 1600, and 2400 mg sodium chloride (NaCl) kg^?1 soil], and four nitrogen (N) levels (0, 60, 120, and 180 mg kg^?1 soil as urea). Treatments were arranged in a factorial manner in a completely randomized design with three replications. The highest level of nitrogen and salinity decreased leaf and root dry weights. Nitrogen application significantly increased the concentration of shoot N and salinity suppressed shoot N concentration. Salinity and nitrogen fertilization increased shoot and root sodium (Na), calcium (Ca), and magnesium (Mg) concentrations. Nitrogen application increased proline concentration and reducing sugar content. Although salinity levels increased proline concentration a specific trend on reducing sugars content was not observed.     

Citric acid influence on soil phosphorus availability

Citric acid is a low-molecular-weight organic acid exuded by the plant roots. Organic anions derived from this acid compete for phosphorus (P) adsorption sites in clay minerals. The objective was to evaluate the P availability by application of P and citric acid tothe soil. For this purpose, an experiment in green house was conducted at the rates of 0, 45, 90, and 180 mg dm^?3 P in Entisol and 0, 100, 200, and 400 mg dm^?3 P in Oxisol, combined with 0, 0.5, 1.0, and 2.0 mg dm^?3 citric acid in pot. In the Entisol, 115 mg dm^?3 of P and 0.7 mg dm^?3 of citric acid resulted in maximum corn growth. However, in the Oxisol, the estimated rates were 299 mg dm^?3 of P and 1.3 mg dm^?3 of acid citric. Citric acid use in Entisol and Oxisol increased P availability of corn plants.     

On-Site Assessment of Extractable Soil Nutrients after Long-Term Biosolid Applications to Perennial Forage

The objective of this study was to evaluate soil nutrient loading and depth distributions of extractable nitrogen (N), phosphorus (P), and potassium (K) after long-term, continuous annual surface applications of anaerobically digested class B biosolids at a municipal recycling facility in central Texas. Commercial forage production fields of coastal bermudagrass (Cynodon dactylon L.) were surface applied at 0, 20, 40, or 60 Mg dry biosolids ha^?1 y^?1 for 8 years. Application duration was evaluated in fields treated with 20 Mg dry biosolids ha^?1 y^?1 for 0, 8, or 20 years. Total soil loads of extractable inorganic N and P increased linearly with application rate, but only extractable P increased with duration. Neither total load nor soil distribution of extractable K was affected by biosolid applications. Mineralization of biosolid-derived organic N and P likely contributed to elevated concentrations of nitrate throughout the soil profile (0–110 cm) and orthophosphate in surface soils (0–40 cm).     

Effect of Fertilizer Nitrogen (N) on Soil Organic Carbon,Total N,and Soil pH in Long-Term Continuous Winter Wheat (Triticum Aestivum L.)

Carbon sequestration via sound agronomic practices can assist in combating global warming. Three long-term experiments (Experiment 502, Experiment 222, and The Magruder Plots) were used to evaluate the effect of fertilizer nitrogen (N) application on soil organic carbon (SOC), total nitrogen (TN), and pH in continuous winter wheat. Soil samples (0–15 cm) were obtained after harvest in 2014, analyzed, and compared to soil test results from these experiments in 1993. Soil pH decreased with increasing N fertilization, and more so at high rates. Nitrogen application significantly increased TN in Experiment 502 from 1993 to 2014, and TN tended to be high at high N rates. Fertilizer N significantly increased SOC, especially when N rates exceeded 90 kg ha^?1. The highest SOC (13.1 g kg^?1) occurred when 134 kg N ha^?1 was applied annually. Long-term N application at high rates increased TN and SOC in the surface soil.     

Effect of Salinity on the Transformation of Wheat Straw and Microbial Communities in a Saline Soil

Currently, straw transformation in saline soil is largely unknown. The effect of soil salinity on wheat straw transformation and the roles of nitrogen (N) and phosphorus (P) were evaluated in a greenhouse experiment. By sodium chloride (NaCl) addition, straw was applied at the rate of 30 g kg^?1 in various saline soils (2.0–4.0 g kg^?1). N or combined N and P added in straw amended saline soil (3.0 g kg^?1). Three replications of each treatment were sampled to determine straw residues at 30, 60, and 90 d. Results showed straw application significantly increased microbial biomass, especially fungal biomass. Soil salinity increased by 1.0 g kg^?1, which decreased straw decomposed rate by 6.3 ~ 11.1%. N application significantly increased straw decomposed rate (p < 0.05), and high salinity obviously inhibited the humidification process of straw. We suggested that straw carbon transformation regulation and little straw residue accumulation in saline soil should arouse more attentions in future studies.     

Interaction between Phosphorus and Nitrogen in Organomineral Fertilizer

ABSTRACT

The aim of this research is to assess the effect of the interaction between phosphorus and nitrogen (P × N) in organomineral fertilizer in the nutrition of plants cultivated in a Typic Hapludox. It was used a completely randomized design in a 5 × 5 factorial scheme with four replications. The treatments corresponded to the equivalent of five doses of P (0, 20, 40, 60, and 80 kg ha^?1 of P) in interaction with five doses of N (0, 50, 100, 150, and 200 kg ha^?1 of N). Three sequential crops of millet were carried out with 40 days of growth each, whose aerial part of the plants was harvested in order to determine the dry biomass and the contents of N and P. After each crop, soil samples were collected from the pot for determination of the forms of P and N. It may be inferred that simultaneous application of N and P into the fertilization does not promote significant changes in the dynamics of N in the soil, but the effect of the interaction is changed over the crop time in the plant. In soil the application of organomineral fertilizers did not show effect of the interaction between P × N on the forms of organic N, inorganic and organic P, except for a difference in the available P, which is the dose of 20P × 200N kg ha^?1 with greater efficiency. In the plant, there was interaction between P × N in organomineral fertilizer on the dry biomass of the aerial part of millet from the dose of 20P × 100N, focusing on the dose of 50P × 150N kg ha^?1, while the accumulation of P and N starts from the dose of 40P × 100N and 40P × 50N kg ha^?1 with an increase (synergy) in both nutrients up to the dose of 80P × 200N kg ha^?1.     

Interactive Effect of Phosphorus and Nitrogen on Leaf Anthocyanins,Tissue Nutrient Concentrations,and Dry‐Matter Yield of Floralta Limpograss during Short Day Length

Abstract

A field trial was conducted during the short‐day period of 2004–2005 at Ona, Fl., to study the factorial effect of nitrogen (67, 90, and 134 kg N ha^?1) and phosphorus (0, 5, 10, 20, and 40 kg P ha^?1) rates on forage dry‐matter yield, quality, nutrient uptake, and leaf pigment concentration of limpograss (Hemarthria altissima). The N and P fertilizers were applied 45 days before each of two harvests. There was no interaction between N and P rates on any of the measured variables. Cool‐season forage yield increased curvilinearly from 137 to 350 kg ha^?1 in winter and 237 to 1389 kg ha^?1 in early spring, whereas crude protein (CP) concentration increased from 145 to 158 g kg^?1, as P was increased from 0 to 40 kg ha^?1, but yield and CP were not affected by N rate. There was a decreasing linear relationship between leaf concentration of anthocyanins and P rate of application such that forage obtained with 0 kg P ha^?1 had 61% more leaf anthocyanins and purple pigmentation than with 40 kg P ha^?1. There was no effect of N on anthocyanins content. It was concluded that increased level of leaf anthocyanins was due to the cumulative stress from cool weather and lower plant‐tissue P levels, which resulted in reduced growth and yield of limpograss. In cool weather, P played a critical role in controlling leaf purple pigmentation and forage yield.     

Soil Fertility,Nutrition and Early Growth of Physic Nut as Affected by Nitrogen Fertilization

The initial growth and mineral nutrition of the physic nut (Jatropha curcas L.) as a function of nitrogen (N) fertilization was investigated. The transplanting of seedlings was carried out in plastic pots filled with 50 dm³ of a Rhodic Hapludox, under a plastic greenhouse. In addition to a control treatment, the dosages of 0, 40, 80, 120, and 160 mg dm^?3 N were tested. The results demonstrated that N fertilization for the cultivation of physic nut could be added as top dressing from 60 days after planting with a dosage of 65 mg dm^?3. A SPAD index of 46 can be used as a nutritional reference to its initial development. Furthermore, the results suggested that the order of nutrient accumulation by the physic nut plants is as follows: potassium (K) > N > magnesium (Mg) > calcium (Ca) > phosphorus (P) > sulfur (S) > iron (Fe) > manganese (Mn) > boron (B) > zinc (Zn) > copper (Cu).     

TREATED EFFLUENT AND SALINE WATER IRRIGATION INFLUENCES SOIL PROPERTIES,YIELD, WATER PRODUCTIVITY AND SODIUM CONTENT OF SNOW PEAS AND CELERY

To determine the effects of irrigation water quality, plants were irrigated with normal potable water [0.25 dS m^?1 electrical conductivity (EC), 25 mg L^?1 sodium (Na), 55 mg L^?1 chloride (Cl)], treated effluent (0.94 dS m^?1 EC, 122 mg L^?1 Na, 143 mg L^?1 Cl) and saline water with low salinity (1.24 dS m^?1 EC, 144 mg L^?1 Na and 358 mg L^?1 Cl) and high salinity (2.19 dS m^?1 EC, 264 mg L ^?1Na and 662 mg L^?1 Cl) for snow peas, and high salinity (3.07 dS m^?1 EC, 383 mg L^?1 Na and 965 mg L^?1 Cl) and very high salinity (5.83 dS m^?1 EC, 741 mg L^?1 Na and 1876 mg L^?1 Cl) for celery. The greater salts build up in the soil and ion toxicity (Cl and Na) with saline water irrigation contributed to significantly greater reduction in root and shoot biomass, water use, yield and water productivity (yield kg kL^?1 of water used) of snow peas and celery compared with treated effluent and potable water irrigation. There was 8%, 56% and 74% reduction in celery yield respectively with treated effluent, high salinity and very high salinity saline water irrigation compared with potable water irrigation. The Na concentration in snow peas shoots increased by 54%, 234% and 501% with treated effluent, low and high salinity saline water irrigation. Similarly, the increases in Na concentration in celery shoots were 19%, 35% and 82%. The treated effluent irrigation also resulted in a significant increase in soil EC, nitrogen (N) and phosphorus (P) content compared with potable water irrigation. The heavy metals besides salts build up appears to have contributed to yield reductions with treated effluent irrigation. The study reveals strong implications for the use of saline water and treated effluent for irrigation of snow peas and celery. The salt build up within the root zone and soil environment would be critical in the long-run with the use of saline water and treated effluent for irrigation of crops. To minimize the salinity level in rhizosphere, an alternate irrigation of potable water with treated effluent or low salinity level water may be better option.     

Response of Lima Bean to Inorganic Nitrogen and Broiler Manure Sources and Rates

Abstract

Applying animal manure to crops is a good disposal practice that also recycles nutrients. A 2‐year study was conducted involving lima bean (Phaseolus lunatus L.) and two N sources, ammonium nitrate (AN, 340 g N kg^?1), and broiler chicken manure (BM, 10 g N kg^?1). The sources were tested at five N rates (0, 67, 135, 202, and 269 kg N ha^?1) in a split‐plot design with N source as the main plot and N rate as the subplot. Treatments were replicated three times in 2000 and four times in 2001. Leaf tissue (early flowering stage) was analyzed for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), iron (Fe), copper (Cu), manganese (Mn) and zinc (Zn). Although most nutrients were within or above the sufficiency range, K and Cu limited crop production for all treatments. There was no difference between N sources for fresh pod yields. The highest fresh pod yield occurred at 213 kg N ha^?1, but the critical point was obtained with 100 kg N ha^?1, a rate agreeing with current University of Florida recommendations.     

Nutrient Uptake of Maize Affected by Nitrogen and Potassium Fertility in a Humid Subtropical Environment

Abstract

Nitrogen (N) and potassium (K) fertility management of maize (Zea mays L.) in the humid subtropical Mississippi Delta may differ from a temperate climate because of its use in rotation with cotton (Gossypium hirsutum L.), soil temperatures rarely falling to 0°C, and heavy winter rains that facilitate nutrient losses. An experiment to determine the [N] (concentration=[ ]), phosphorus [P], [K], calcium [Ca], magnesium [Mg], iron [Fe], manganese [Mn], zinc [Zn], and copper [Cu] and their total contents plant^?1 of maize grown in rotation with cotton, using N fertility levels of (134, 179, 224, 269, and 314 kg N ha^?1) in combination with K fertility levels of (0, 45, 90, and 134 kg K ha^?1) was conducted in 2000 and 2001 at Tribbett, MS. Ear leaves, immature ears, and husks collected at growth stage R2 and grain and stover collected 21 days after R6 were dried, weighed, and analyzed for nutrient concentration. Plots were also harvested for yield, kernel weight, grain bulk density, and harvest index (HI). Increased [N] values of about 1.3 mg g^?1 occurred in all organs except the stover between 134 and 314 kg N ha^?1 N fertility. Stover [N] increased approximately 3.0 mg g^?1 within the same N fertility range. Total N content of ear leaves, grain, and stover increased by about 11.0, 550.0, and 730.0 mg plant^?1, respectively, with N fertility increased from 134 to 314 kg N ha^?1. Yields, kernel weights, grain bulk densities, and harvest indices also increased with added N fertility. Several micronutrient concentrations and contents increased as N fertility increased. Increased K fertility had only limited influence on concentrations of most nutrient elements. The nutrient contents of most elements in the stover increased with added K fertility compared with plots that received no supplemental K fertilizer. These data showed between 139 and 265 kg N ha^?1 was permanently removed by grain harvest and suggest that N fertility recommendations for the Mississippi Delta may be low for maize yield goals above 10 Mg ha^?1. Added K fertilizer has minimal benefit to maize when soil test levels are adequate but are important to succeeding cotton crops where K uptake during fruiting can exceed the soil's ability to release K for uptake.     

Phosphorus Sources and Rates Associated with Nitrogen Fertilization in Mombasa Grass Yield

Nitrogen (N) and phosphorus (P) deficiency is one of the important causes of degradation of cultivated pasture under tropical conditions. The aim of this study was to evaluate phosphate rates and sources, and N rates on the concentration and uptake of N and P, and shoot dry mass (SDM) yield of Megathyrsus maximum grass cv Mombasa in an Ultisol. The trial was carried out in a greenhouse in pots with 4.0 dm^?3 of soil. The experiment was arranged in a completely randomized design with four replicates. The 3 × 3 × 3 factorial treatments consisted of phosphorus sources [reactive rock phosphate from Morocco (RPM), reactive rock phosphate from Algeria (RPA) and triple superphosphate (TSP)], three phosphorus rates (0, 150, and 300 mg kg^?1), and three N rates (0, 250, and 500 mg kg^?1). The SDM and tillering of Mombasa grass were significantly influenced with the TSP, RPM, and RPA application associated with N fertilization. The RPM, RPA, and TSP met the nutritional demands of Mombasa grass. The three P sources showed the same effect on the total N uptake by Mombasa grass. The P use efficiency (PUE) when fertilizer-P sources were added alone by Mombasa grass was <12% of the added P, and PUE decreased as follows: TSP > RPA > RPM. When P and N-fertilizer were added together, the fertilizer-N use efficiency (NUE) was 62%. The reactive phosphate (RPM and RPA) is an efficient P sources for Mombasa grass, but requiring higher rate of application compared to TSP source.     

Zeolite influences on nitrate leaching,nitrogen-use efficiency,yield and yield components of canola in sandy soil

With regard to the low cation-exchange capacity and large saturated hydraulic conductivity of sandy soils, a field experiment was carried out in 2006–2007 to determine the impact of zeolite on nitrogen leaching and canola production. Four nitrogen (N) rates (0, 90, 180, and 270 kg ha^–1) and three zeolite amounts (3, 6 and 9 t ha^?1) were included as treatments. The results demonstrated that the highest growth parameters and seed yield were attained with 270 kg N ha^?1 and 9 t zeolite ha^?1. However, the highest and the lowest seed protein percentage and oil content were obtained with 270 kg N ha^?1 accompanied by 9 t zeolite ha^?1, respectively. Nitrate concentration in drained water was affected by nitrogen and zeolite. The lowest and highest leached nitrate values were found in control without N and zeolite (N₀Z₀) and in treatments with the highest N supply without zeolite (N₂₇₀Z₀), respectively. In general, nitrogen-use efficiency decreased with an increase in N supply. Application of 9 t zeolite ha^?1 showed higher nitrogen use efficiency than other zeolite amounts. Also, application of more N fertilizer in soil reduced nitrogen uptake efficiency. In total, application of 270 kg N ha^?1 and 9 t zeolite ha^?1 could be suggested as superior treatment.     

Nitrogen Balance in the Magruder Plots Following 109 Years in Continuous Winter Wheat

Abstract

The Magruder plots are the oldest continuous soil fertility wheat research plots in the Great Plains region, and are one of the oldest continuous soil fertility wheat plots in the world. They were initiated in 1892 by Alexander C. Magruder who was interested in the productivity of native prairie soils when sown continuously to winter wheat. This study reports on a simple estimate of nitrogen (N) balance in the Magruder plots, accounting for N applied, N removed in the grain, plant N loss, denitrification, non‐symbiotic N fixation, nitrate (NO₃ ^?) leaching, N applied in the rainfall, estimated total soil N (0–30 cm) at the beginning of the experiment and that measured in 2001. In the Manure plots, total soil N decreased from 6890 kg N ha^?1 in the surface 0–30 cm in 1892, to 3198 kg N ha^?1 in 2002. In the Check plots (no nutrients applied for 109 years) only 2411 kg N ha^?1 or 35% of the original total soil organic N remains. Nitrogen removed in the grain averaged 38.4 kg N ha^?1 yr^?1 and N additions (manure, N in rainfall, N via symbiotic N fixation) averaged 44.5 kg N ha^?1 yr^?1 in the Manure plots. Following 109 years, unaccounted N ranged from 229 to 1395 kg N ha^?1. On a by year basis, this would translate into 2–13 kg N ha^?1 yr^?1 that were unaccounted for, increasing with increased N application. For the Manure plots, the estimate of nitrogen use efficiency (NUE) (N removed in the grain, minus N removed in the grain of the Check plots, divided by the rate of N applied) was 32.8%, similar to the 33% NUE for world cereal production reported in 1999.     

Nitrogen Availability for Maize from a Rolling Pampa Soil After Addition of Biosolids

Abstract

The objective of this paper was to evaluate the influence of different rates of biosolids on the soil nitrogen (N) availability for maize and its residuality. A field experiment was developed in a typic Argiudol located in the NE of the Buenos Aires Province. Maize was sown for two consecutive years 1997–1999. Biosolids from a sewage treatment plant of Buenos Aires outskirts were superficially applied to the soil and incorporated by plowing. There were eight treatments: Check; 8, 16, and 24 Mg of dry biosolid ha^?1; 8 and 16 Mg of dry biosolid ha^?1 applied one year before, 100 and 150 kg N ha^?1 of calcium ammonium nitrate (CAN). The sampling and determinations were done during the second maize cycle. At presowing (PS), sowing (S), 6 expanded leaves (V6), 12 expanded leaves (V12), and Flowering (Fl) composite soil samples from 0–40 cm depth were obtained to determine ammonium and nitrate contents. At Fl maize plants were sampled in order to determine total biomass and N content. The N‐nitrate content in the soil was significantly increased by the biosolids application (p < 0.05), and varied for each increment depending on the biosolids rates and the phenological stage. After 30 days from the incorporation the increases of 1.19, 1.34, and 2.05% were observed for N‐nitrates for 8, 16, and 24 Mg ha^?1, respectively. The contribution of mineral N from the biosolids was 2.48, 6.46, and 5.01 kg N Mg^?1 when the rates were incremented from 0–8, 8–16, and 16–24 Mg ha^?1, respectively. The nitrogen mineralization followed a release pattern with a maximum value of 296 kg N‐nitrate ha^?1 at sowing for 24 Mg ha^?1. Since then, the release of mineral nitrogen decreased significantly till Fl. The N‐nitrates values variation with the temperature adjusted to polinomic functions. The mineral N released from the biosolids increased as a response to the increment of soil temperature and then decreased due to the maize nitrogen absorption and the potentially mineralized nitrogen exhaustion. The application of 150 kg N ha^?1 as CAN incremented significantly the soil N‐nitrate content and equalized 16 and 24 Mg of dry biosolids ha^?1 at V6. But, no synchronism between the high nitrate releasing from biosolids and the increment in the nitrogen absorption by maize was observed. This fact generates a surplus of nitrate that incremented the potential of nitrogen loss by lixiviation. We observed a residual effect from the biosolids that were applied the previous year. This contribution represented the 35% of the maize requirements and was similar to the nitrate content observed in Bio 16. The biosolids might be a valuable source of nitrogen for maize crop if the synchronism between the soil supply and maize demand is observed in order to avoid nitrates surplus.     

Soil Factors Affecting Yield,Quality, and Response to Nitrogen of Sugar Beets Grown on Light-Textured Soils in Northern Greece

For 7 years (1997–2003), five nitrogen (N) rates (0, 60, 120, 180, and 240 kg N ha^?1) were applied to sugar beets arranged in randomized complete block (RCB) design experiments with six replications and grown on light soils (sand content >50 g kg^?1) in northern Greece. The aim of this work was to identify soil characteristics that affect yield, quality, and sugar beet response to N fertilization. Before sowing, soil analyses were conducted in control plots (0 kg N ha^?1) at two depths (0–30 and 30–60 cm). Soils differed in their physical and chemical properties and especially in sand content, which ranged from 500 to 732 g kg^?1. Quantitative (root number, RN; root yield, RY; and sugar yield, SY) and qualitative (percentage sucrose content in fresh root weight, SC; potassium, K; sodium, Na; and α-amino N) traits of control plots were used as soil fertility index. The RN was positively affected by clay content, and RY and SY were positively related with sand and negatively with silt content. The SC was negatively affected by soil (NO₃)-N and sodium (Na) concentrations. Also, soil (NO₃)-N concentration was positively related with root impurities (K, Na, α-amino N). In combined data over years, N rates had a negative effect on the RN. The RY was the only trait affected by years, N rates, and their interaction. The SC and SY differed significantly between years, and N rates affected significantly the former but not the latter. In combined data over years, N rates were curvilinearly related with Na concentration in roots, whereas a strong, linear relationship was found between α-amino N concentration and N rates. To study the significant years × N rates interaction evidenced for the RY, the relative response (RR) of the RY to N was introduced. Actually, the RR expresses the increase or decrease of the RY for a 150 kg N ha^?1 rate compared to the control (0 kg N ha^?1). The RR was strongly related with soil K concentration at the 0- to 30-cm depth (y = –0.00002x² + 0.0082x + 0.5085, r² = 0.92, P < 0.01, n = 7) and with total N concentration at the deeper layer (y = 1.8335x² – 3.5312x + 2.6614, r² = 0.88, P < 0.05, n = 6). Thus, the RY response to a rate of 150 kg N ha^?1, which is the commonly applied to the sugar beet crop in Greece, can be predicted reliably by soil characteristics (K and total N concentration) determined before sowing. The strong relationship between soil K concentration and sugar beet response to N merits further research.     

Effect of Nitrogen on the Alleviation of Boron Toxicity in Rice (Oryza Sativa L.)

Pot experiments were conducted in the greenhouse on a calcareous soil to study effect of nitrogen (N) on the alleviation of boron (B) toxicity in rice. The treatments consisted of factorial combination of six levels of B (0, 2.5, 5, 10, 20, and 40 mg kg^?1 as boric acid), and four levels of N (0, 75, 150, and 300 mg kg^?1 as urea) in a completely randomized design with three replicates. Boron addition (higher than 2.5 mg kg^?1) significantly reduced the seeds yield. Nitrogen addition alleviated the growth suppression effects caused by B supplements. Yield was increased by application of 2.5 mg B kg^?1 at all N levels, but at higher levels, B significantly decreased the yield of rice. Boron concentration declined with increasing N levels. Boron application increased the concentrations of B, potassium, phosphorous (P), and zinc. Nitrogen application decreased the concentration of Zn and increased the concentration of N and P.     

Boron Availability in Building up Fertility in Cerrado Soil of Tocantins

ABSTRACT

The expansion of agricultural activity in the Cerrado biome raises the importance of building soil fertility in micronutrients, however, the dynamics of these elements in different soil classes remains to be understood. The objective aimed to evaluate the availability of boron (B) in the soil in function of sources and incubation times to build the fertility of Oxisol and Entisol (Quartzipsamment). The experimental design was completely randomized with 50 treatments obtained in a 5 × 10 factorial scheme, being: five sources (boric acid, sodium octaborate, sodium tetraborate, boron oxide, and boron oxisulphate) and ten incubation times (0, 5, 10, 15, 25, 40, 55, 70, 85 and 100 days), with three repetitions. For all sources, the applied B dose was 4.0 mg dm^?3 in soil samples of 0.5 dm³, with pH corrected to 6.0. In the two soils evaluated, borate fertilization promoted significant effects (p ≤ 0.05) on the availability of B and the efficiency of fertilization over the incubation time. The highest levels of B available in soils resulted from the use of less soluble sources, representing a fertilization efficiency above 75% when using boron oxisulphate in the Oxisol and greater than 85% with the use of boron oxide in the Entisol. The sources of greater solubility achieved an average efficiency of 10.66%. It is concluded that fertilization with borate sources affects the availability of boron to the building of soil fertility, however, the most soluble ones are less efficient to maintain good availability (>0.5 mg dm^?3) after 40 days of application.     

Influence of Long‐Term Sodic‐Water Irrigation,Gypsum, and Organic Amendments on Soil Properties and Nitrogen Mineralization Kinetics under Rice–Wheat System

Abstract

Influence of long‐term sodic‐water (SW) irrigation with or without gypsum and organic amendments [green manure (GM), farmyard manure (FYM), and rice straw (RS)] on soil properties and nitrogen (N) mineralization kinetics was studied after 12 years of rice–wheat cropping in a sandy loam soil in northwest India. Long‐term SW irrigation increased soil pH, exchangeable sodium percentage (ESP), and sodium adsorption ratio (SAR) and decreased organic carbon (OC) and total N content. On the other hand, application of gypsum and organic amendments resulted in significant improvement in all these soil properties. Mineralization of soil N ranged from 54 to 111 mg N kg^?1 soil in different treatments. Irrigation with SW depressed N mineralization. In SW‐irrigated plots, two flushes of N mineralization were observed; the first during 0 to 7 d and the second after 28 d. Amending SW irrigated plots with GM and FYM enhanced mineralization of soil N. Gypsum application along with SW irrigation reduced cumulative N mineralization at 56 days in RS‐amended plots but increased it under GM‐treated, FYM‐treated, or unamended plots. Nitrogen mineralization potential (N_o) ranged from 62 to 543 mg N kg^?1 soil. In the first‐order zero‐order model (FOZO), the easily decomposable fraction ranged from 5.4 to 42 mg N kg^?1 soil. Compared to the first‐order single compartment model, the FOZO model could better explain the variations in N mineralization in different treatments. Variations in N_o were influenced more by changes in pH, SAR, and ESP induced by long‐term SW irrigations and amendments rather than by soil OC.     

RESPONSE OF MAIZE GROWN IN AN ALFISOL OF SRI LANKA TO INOCULANTS OF PLANT GROWTH PROMOTING RHIZOBACTERIA

Field experiments were conducted to assess the ability of rhizobacterial inoculants to enhance growth and yield of maize. Performances of two phosphorus (P)-solubilizing bacteria in combination with a fertilizer mixture containing rock phosphate and triple super phosphate (PFM), and five diazotrophs combining either with 150 kg or 100 kg nitrogen (N) ha^?1 supplied as urea were compared with non-inoculated-fertilized controls. Shoot P and N and soil available P and N contents were assessed and shoot biomass and ear weights were recorded at harvest. Pseudomonas cepacia resulted in significantly higher available P (51 mg P kg^?1 soil), P accumulation (3.6 g kg^?1 dry matter) and 13% increase in shoot biomass over control. Azospirillum sp. and dual inoculant comprising Enterobacter agglomerans + Agrobacterium radiobacter led to significantly higher available N (74–94 mg kg^?1 soil) and 19 to 26% increase in shoot biomass over the control. However, inoculants did not increase the yield significantly.