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Nitrogen (N) fertilizer use efficiency seldom exceeds 50% and the surplus N is either escapes to the atmosphere or enters groundwater in the forms of ammonia, or nitrous oxide, nitrates, hampering air, water, and soil quality. Managing N transformations from N fertilized soils are thus vital to enhance nitrogen use efficiency (NUE) and decreasing N losses. The use of nitrification inhibitors (NIs) is a tested strategy to manage nitrification, the first step towards N loss in the form of nitrates and nitrous oxides in the soil. The current study was conducted to evaluate the influence of neem oil (Azadirachta indica) coated prilled urea (NOCU) and pomegranate (Punica granatum) leaf extract coated prilled urea (PLECU) in comparison with dicyandiamide (DCD) blended urea; for mineral N (NH4-N and NO3-N) release in soil, nitrification inhibition (NIH), and apparent nitrification rate (NIR). The results indicated that maximum nitrification inhibition (NIH) (26-64%) was shown by DCD followed by the NOCU in the range of (15-50%) and the least NIH (4-39%) was indicated by PLECU. However, the maximum apparent nitrification rate (NIR) of 73% was calculated in urea only treatment, and the lowest NIR of 32% was shown by DCD. Dicyandiamide showed maximum NIH than other treatments followed by NOCU, and the least NIH was observed in treatment receiving PLECU. Hence, it is recommended that these substances could be used successfully for the slow release of N by manipulating N transformations in the soil, and enhanced N efficiency can be achieved in agroecosystems. The results warrant further field studies considering various soil and crop-related parameters in different agroecological zones. [ABSTRACT FROM AUTHOR]

Wastes materials produced from bio-energy plants such as ash, slurry etc., may be problematic if they are not safely disposed. The wastes utilization as soil amendments is a viable approach as these are rich source of mineral nutrients. Therefore, the present experiment was conducted to evaluate the nutrient release and changes in physicochemical properties of soil after incubation with a different combination of bio-energy residues. Two variants of sugarcane bagasse ash, (A) combustion ash from sugarcane industry and (G) ash from gasification plant were mixed in 1:1 ratio with wheat straw biochar (B) and dairy manure digestate (D) @ 10, 15 and 20 t ha-1. Soil samples were taken after 15, 30, 45, and 60 days of incubation and analyzed for soil physico-chemical and biological parameters. Various amendments significantly influenced the soil pH, electrical conductivity, soil respiration, P, and K contents at each sampling interval. The P and K contents in soil amended with digestate+ combustion ash were significantly increased after 60 days of incubation compared to their initial soil contents. Ammonium contents were increased up to 15 days of incubation and then decreased while nitrate contents increased in the same treatment. While macro-aggregate (77 g kg-1) and organic carbon contents (1.40%) were maximum in biochar + combustion ash treatment. The application of bioenergy wastes improved respiration, soil organic carbon, soil P and K contents. The study warrants that these wastes combinations should be tested under field conditions for further recommendations. [ABSTRACT FROM AUTHOR]

Currently 50% of the Pakistani soils are reported deficient in potassium (K) along with iron (Fe) due to alkaline calcareous nature. Intensive cropping of exhaustive crops has resulted in negative K and Fe balance and subsequent population also suffering from iron deficiency. Application of nanotechnology with the idea of enhanced bio-availability, reactivity, surface area and adhesive effect of nano materials has made it a revolutionary tool for enhanced crop growth and nutrient enrichment in agriculture. A field study was conducted to assess the effect of potassium ferrite (KFeO2) nano coated diammonium phosphate (DAP) fertilizer on the growth attributes, yield parameters and uptake of nutrients by wheat crop. Results showed that plant height, shoot fresh and dry weight, chlorophyll contents, N, P, K and Fe uptake in shoot (at tillering and booting stage) and in grains and straw were significantly higher in treatment where recommended NP +10% KFeO2 nano-coated DAP was applied. Similarly, grain and straw yield was significantly improved in NP10 treatment than all other coated and uncoated treatments. The treatment NP (RD NP from DAP, urea + no potassium (farmer common practice) showed the least effect on growth parameters, yield attributes and harvest index. The treatment with 75% RD of coated DAP + 25% of K showed statistically similar grain yield compared to NPK that indicated a positive and promising effect of K and Fe nanoparticles. It was concluded from the study that nano coated DAP was a practical approach that may be adopted for enhanced plant growth and yield attributes of wheat crop. It also improves the potassium and iron contents of wheat grain, which is beneficial for human health. [ABSTRACT FROM AUTHOR]

The soil salinity causes physiological drought resulting in hindrance in the bio-availability of essential nutrients. The interaction between salinity and phosphorus uptake by plants is less explored. Two independent incubation experiments were conducted to study the distribution and transformation of various P fractions in normal and salt affected soils as influenced by various organic amendments application. In first experiment, three different levels of P (200, 400 and 600 mg kg-1 of soil) were applied in three soils differing in soil EC and SAR. Changes in various fractions of soil P (Ca2-P, Ca8-P, Al-P, Fe-P, Olsen-P) were estimated at different time intervals. All three soils behaved differently for P distribution among various fractions. Maximum available P (12.18 mg kg-1) was found in PROKA soil (saline sodic) at 400 mg kg-1 of P applied. In 2nd experiment, various organic amendments [farmyard manure (FYM), poultry manure (PM), crop residue (CR)] and sewage sludge (SS) were used, with and without adding P fertilizer @ 400 mg kg-1 to study their effect on changes in soil P, at different time intervals. Plant available Olsen-P fraction significantly increased after 90 days in all soils (normal, saline sodic, marginal saline sodic) with amendments FYM and PM but not as much with amendments CR and SS. Overall, increase in Olsen-P was higher with PM (23.2, 21.7 and 19.4 mg kg-1) and FYM (20.6, 17.6 and 20.6 mg kg-1) as compared with SS (14.3, 15.5 and 15.7 mg kg-1) and CR (12.9, 14.4 and 14.0 mg kg-1) in normal, saline sodic and marginal saline sodic soils, respectively. On the basis of these results, it was concluded that integration of PM and FYM with P level 400 mg kg-1 is an effective approach to mobilize more P available for plant uptake in normal and salt-affected soils with order of normal> saline sodic> marginal saline sodic. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is the most widely applied plant nutrient and is a key constituent of animal manures. Improvement in crop yields and high economic returns have been made possible through supplementation of crops with organic and inorganic fertilizers. The movement of N in the environment has been extensively studied and documented. The fate of N ranges from nitrification, denitrification, nitrous oxide formation, leaching of nitrate, and volatilization of ammonia. Even with this knowledge the variation in N movement within the soil, air and water varies greatly with changed edaphic factors. For instance the fate of N fertilizer under calcareous soil systems still has not been investigated widely. We reviewed the sporadic information available on N fate and management in calcareous soils especially in Pakistan. We discussed the sources and fate of N in calcareous soils of Pakistan and also the currently adopted and newly developed method to reduce the N losses. [ABSTRACT FROM AUTHOR]

Salinity stress is a major abiotic factor limiting growth and yield of agronomic crops including maize. The present study was conducted to categorize the latest maize cultivars according to their tolerance against salinity stress and to screen out the salt tolerant and sensitive maize cultivars at different growth stages. Initially 15 maize cultivars were categorized into three classes viz sensitive, medium and tolerant to salinity on the basis of germination parameters under control and 90 mM NaCl salinity. Eight selected cultivars were germinated in petri plates with 90 mM NaCl and 2 mM K2SiO3 in a second experiment. Application of Si increased all germination parameters under salinity stress irrespective of cultivars. Two cultivars contrasting in their salinity tolerance at germination (Syngenta 8441 and EV1089) were selected to evaluate role of Si at vegetative growth stage. Plants were grown in pots with 60 mM NaCl and 2 mM H2SiO3. Significant variation existed in both cultivars for growth and ionic concentration. Cultivar EV1089 performed better in non-saline conditions than Syngenta 8441; however, it could not tolerate salinity in root zone and significant reduction in biomass observed. Silicon application improved growth in both cultivars under salinity stress by reducing Na uptake and improving K uptake. Silicon nutrition management and selection of salinity tolerant cultivars can improve productivity of salt affected lands and more area can be taken under cultivation to feed ever increasing population. [ABSTRACT FROM AUTHOR]

Higher grain Zn concentration is desirable to combat human Zn deficiency. A total of 58 farmers' fields were surveyed from districts of Multan and Lodhran to represent cotton-wheat rotation zone of Punjab. Soils were sampled separately from the surface (0–15 cm depth) and subsurface (15–30 cm depth) layers. Within 5 m2 of soil sample, about 100 spikes from mature tillers of wheat were also collected. Nearly all subsurface and 76% of the collected surface soil samples were deficient in plant available Zn resulting in grain Zn concentration of 20 µg g–1, on average. The inherent capacity of subsurface soil layer to supply Zn positively correlated with grain Zn concentration (r=0.33, n=58; P=0.01). Organic matter content (r=0.32, n=58; P=0.02) in subsurface layer and soil salinity (ECe) of both layers (r=–0.53, n=58; P<0.01 for ECe of both layers) were the other major soil characteristics that significantly correlated with grain Zn concentration. Zinc bioavailability in wheat grains, estimated by [phytate]:[Zn] ratios and trivariate model of Zn absorption, was low. Present study indicated a need to reduce current grain [phytate]:[Zn] ratio (46, on average) and to increase the current trivariate model based estimated Zn bioavailability (1.5 mg Zn for 300 g flour, on average) by about 2-folds. Conclusively, Zn fertilization strategy for southern Punjab was suggested as a solution to human Zn deficiency and low grain yields. [ABSTRACT FROM AUTHOR]

Zinc (Zn) deficiency and boron (B) toxicity are often encountered simultaneously in soils of semi-arid and arid regions. A sand culture experiment was conducted to evaluate the alleviation of B toxicity by application of Zn to barley genotypes. Two barley cultivars [Clipper (B toxicity sensitive/Zn-inefficient) and Sahara (B toxicity tolerant/Zn-efficient)] were grown with four B (0.1, 0.5, 1.5 or 3 mg kg-1) and two Zn (0.1 or 1.0 mg kg-1) levels, for 35 days. High rates of B significantly reduced plant dry matter, more prominently in Clipper. Application of Zn significantly improved shoot and root dry matter in Clipper in all B treatments. Boron application significantly increased B in shoots and roots of both genotypes, but the increase was more prominent in Clipper than Sahara. Boron concentration in roots of Clipper was almost double that in Sahara irrespective of Zn and B treatments. Application of Zn at 3.0 mg Zn kg-1 decreased B concentration in both cultivars. Higher Zn concentration in Sahara resulted in lower B:Zn concentration ratio than Clipper. The interactive effects of B and cultivars suggested the possible use of genetic variations for ameliorating B toxicity and Zn deficiency. [ABSTRACT FROM AUTHOR]

Zinc biofortification of cereal grains is suggested for controlling widespread human Zn deficiency in developing countries. In present field trail, various Zn treatments [control, priming of seeds in 0.5% (w/v) Zn solution (seed priming), dipping of roots in 0.5% (w/v) Zn solution (root dipping), application of 20 kg Zn ha–1 (soil application), sprays of 0.25% (w/v) Zn each at tillering and heading stages (foliar application) and combination of soil + foliar Zn applications] were applied as ZnSO4·7H2O to rice grown under submerged conditions on a Zn deficient calcareous soil. Treatments significantly (P≤0.05) increased grain and straw yield; however, seed priming and root dipping increased paddy yield only by ≤5%. Increased grain weight also significantly increased grain phytate content. Whole grain Zn concentration increased from 22 (at control) to 29 mg kg–1 (at soil + foliar application).Zinc applications methods, especially soil + foliar application, decreased grain [phytate]:[Zn] ratio and increased estimated human Zn bioavailability in grains based on trivariate model of Zn absorption. Conclusively, soil + foliar Zn application is suitable for optimum paddy yield and agronomic Zn biofortification of rice grains. However, a limited increase in grain Zn concentration (7 mg kg–1) by Zn application suggested exploitation of molecular and genetic approaches in Zn biofortification programs. [ABSTRACT FROM AUTHOR]

Iron availability in alkaline and calcareous soils is limited because of high pH and calcium carbonate contents. Various sources may have different solubilities within soil and may result in varying degrees of Fe availability. An incubation study was conducted to evaluate effectiveness of different sources of Fe to maintain water soluble Fe in different soils over passage of time. For this purpose, three different soils were incubated with various organic (Fe-EDDHA, Fe-DTPA, FYM) and inorganic (ferrous sulphate, vivianite) Fe sources for the period of four weeks. All amendments were adjusted to maintain 20 mg kg-1 of soil Fe except FYM. Iron sources showed significantly different behavior in maintaining soil Fe in different soils. The chelates of Fe proved very effective in maintaining soil solution Fe throughout the incubation period. Fe-EDDHA maintained 12 mg kg-1 with 56% recovery of total Fe added Followed by Fe-DTPA (with 30% recovery). Recovery of ferrous suphate was negligible on the first day of incubation. Vivianite which was prepared by mixing DAP fertilizer with FeSO4.7H2O also rapidly converted in to insoluble fractions on first contact to soils but maintained slightly more amount of soluble Fe as compared ferrous sulphate. [ABSTRACT FROM AUTHOR]