Critical soil level of zinc for wheat grown in alkaline soils

Wheat plants were grown to study the effect of Zn application in a screen house experiment involving 19 alkaline soils having a range of DTPA extractable Zn and widely divergent physical and chemical properties. Soil Zn was positively correlated with organic carbon, clay, Olsen's P and Bray's per cent yield (r = 0.54^*, 0.67^**, 0.54^* and 0.84^**) respectively. There was a significant increase in the leaf, grain and total dry matter yield of plants due to Zn fertilization but no such effect was obvious in stem. Concentration of Zn in different plant parts increased significantly with its application in all the soils irrespective of the initial Zn status. Statistical method indicated 0.65 mg kg^–1 as the critical level of Zn in alkaline soils below which responses to Zn fertilization may be expected in case of wheat.     

Evaluation of soil extractants for Mn availability and response of wheat to applied Mn in soils of semi-arid zone of Punjab, India

Seven chemical extractants were tested for their relative performance to predict the response of wheat to Mn application in coarse textured alkaline soils of semi-arid region. Five out of the seven extractants were found to be promising for the estimation of critical level of available Mn in these soils, as the amount of Mn extracted by these extractants was positively and significantly correlated with relative grain yield as well as Mn uptake. The critical deficiency level of soil available Mn with 0.005 M DTPA, 0.02% hydroquinone, 0.02 N sodium pyrophosphate, 0.1N H3PO4 and 0.05N HCl+0.025N H2SO4 was 3.1, 13.8, 23.5, 5.3 and 17.8 mg kg-1 soil, respectively. The 1N ammonium acetate and 0.01M CaCl2 were found to be unsuitable extractants for these soils. Further field trials at eight locations with varying levels of Mn deficiency showed successive increase in the grain yield of wheat with foliar Mn application, emphasizing the need for Mn fertilization when wheat is grown on Mn deficient soils.     

Determination of critical level of zinc in non-calcareous soils for predicting response of wheat to applied zinc

Studies were conducted in ten non-calcareous arid brown soils (India) to determine the critical level of soil Zn for predicting response of wheat to zinc fertilization. The per cent mean response at 5 mg kg^–1 added Zn varied from 1.3 to 51.4 with a mean value of 17.5 per cent over control in terms of grain yield (g pot^–1). Further, Zn application resulted in significant increase in Zn concentration in various plant parts in all the soils irrespective of the initial Zn status. The critical level of Zn in soil and plant below which response to applied Zn may be expected was found to be 1.75 mg kg^–1 for 0.1 N HC1 extractable soil Zn and 1.7 mg kg^–1 for plant tissue Zn.     

Critical manganese deficiency level for soybean grown in Ustochrepts

A greenhouse study with 15 soils, having a range in DTPA extractable Mn, was conducted to determine the critical deficiency level of Mn in Ustochrepts for predicting response of soybean to Mn application. Soil application of 10 mg Mn kg^–1 soil significantly increased the dry matter yield in deficient soils. Soil Mn was significantly related with Bray's per cent yield (r = 0.72^**) and Mn uptake (r = 0.75^**). Both graphical and statistical models of Cate and Nelson indicated the critical level to be 3.3 mg kg^–1 soil of DTPA extractable Mn. Critical Mn deficiency level in recently matured terminal leaflet blade at V6 growth stage in soybean plant was 22.0µg g^–1 dry matter. The predictability of soil and plant critical Mn level was 87 per cent.     

Chemical assessment of the zinc status of some soils of the semi-arid region of India

To find critical tissue levels of Zn for wheat, and to evaluate various chemical extractants, a screen-house experiment was conducted on 21 diverse soils representing semi-arid regions in Haryana State, India. The extractants differed in the amounts of Zn extracted and the order was: 0.1 N HC1 > EDTA-NH₄OAc > EDTA-(NH₄)₂CO₃ > DTPA + CaCl₂. The amounts (mg kg^–1) of extractable Zn associated with a yield reduction of 20% were: DTPA + CaCl₂, 0.60; EDTA — (NH₄)₂CO₃, 0.80; EDTA-NH₄OAc, 0.92 and 0.1 N HCl, 1.20. The corresponding critical Zn concentration in ten weeks old plants was found to be 17 mg gm^–1. The DTPA + CaCl₂ method gave the best correlation (r = 0.85) between extracted Zn and Bray's per cent yield. It is recommended for assessing Zn status of soils of semi-arid region.     

Phosphate sorption approach for determining phosphorus requirements of wheat in calcareous soils

Five field experiments involving P application rates from 0 to 66 kg P ha^–1 were conducted on irrigated wheat at Tandojam, Pakistan. The soils belonged to two great soil groups, Torrifluvent and Camborthid. All soils were calcareous. Olsen-P contents ranged from 3.5 to 6.3 mg P kg^–1. Phosphate sorption curves were developed for soils from control (no P) plots at each site. Concentrations of P in solution established by fertilization in the field as estimated from the sorption curves ranged from 0.008 to 0.16mg P L^–1. Actual grain yields were converted to relative grain yields and plotted against corresponding concentrations of P in solution. Yield response to P application was obtained in each experiment. Control plot yields ranged from 57 to 89% of maximum yield of respective experiments. Phosphorus requirements of wheat were 0.032 mg L^–1 for 95% yield as determined from a composite yield response curve. Predicted quantities of P required to attain 0.032 mg P L^–1 ranged from 18 to 29 kg P ha^–1. The results of the study suggest that the P sorption approach can be used as a rational basis for making P fertilizer recommendations for various soil-crop combinations.     

Critical levels of Mn in coarse textured rice soils in India for predicting response of barley to Mn application

Green house studies of 20 soils, having a range in DTPA extractable Mn, were made to determine the critical deficiency level of Mn for predicting response of barley to Mn application. Soil Mn was significantly related with both Bray's per cent dry matter yeild (r = 0.70^**) and Mn uptake (r = 0.65^**). Soil application of 25 mg Mn kg^–1 soil significantly increased yield. Both graphical and statistical models of Cate and Nelson indicated the critical level to be 2.05 mg kg^–1 soil of DTPA extractable Mn. The critical Mn deficiency level in 45 day barley plants was 18.6 mg kg^–1 dry matter. The predictability of soil and plant critical Mn level was 91 and 80 per cent respectively.     

Evaluation of iron oxide impregnated filter paper method as an index of phosphorus availability in paddy soils of Tanzania

Phosphorus is a major yield limiting nutrient in rice production and yet most soil test methods for predicting P availability to plants have a number of shortcomings especially under flooded conditions. The objective of this study was to evaluate the iron oxide impregnated filter paper (Pi) method for assessing changes in P availability in soils subsequent to flooding and to determine the suitability of the method in assessing P status in paddy soils. The results indicated that available P increases considerably (between 34% and 256%) subsequent to flooding and this affected responsiveness of the soils to P application. Two versions of the Pi method namely; the Pi method used under flooded conditions (Pi-P_f) and Pi strips embedded directly in flooded soils (Pi-P_fe) were effective in assessing P availability in paddy soils. The two Pi methods were better correlated with rice dry matter yield than the traditional soil tests and are hence recommended for use in soil testing under flooded conditions. The tentative critical levels of P for the two procedures under pot conditions were 22 mg/kg for Pi-P_f and 15 mg/strip for Pi-P_ef.     

The effect of zinc fertilizer on take-all and the grain yield of wheat grown on zinc-deficient soils of the Esperance region,Western Australia

Wheat plants were grown in field experiments with five levels of zinc (Zn) fertilizer applied to plots in 1983. The plots were continuously cropped with wheat to allow the build up ofGaeumannomyces graminis var.tritici (Ggt). For experiments 1 and 2, there were high levels of Ggt in the second and third years while for experiment 3 there were high levels of Ggt incidence in the third and fourth year of continuous cropping. The Zn status of the wheat plants, grain yield, and the incidence and severity of take-all were measured for every experiment each year.The Zn-deficient wheat plants were more severely infected by Ggt. However, increasing the Zn supply beyond that required for maximum grain yield had no further effects on decreasing the severity of take-all. The Zn concentration in the youngest emerged blade (YEB) suggested that the Zn status of the wheat plant ranged from severely Zn-deficient through marginal deficiency to sufficiency.The Zn-deficient wheat plant was more susceptible to Ggt infection than Zn-adequate plants. The severity of take-all in the final year was still high in Zn-adequate plants, suggesting high levels of applied Zn (11.2 kg Zn/ha in 1983) had no fungistatic effect on Ggt.     

Methods and rates of application of Mn and its critical levels for wheat following rice on coarse textured soils

Two field experiments were conducted on Mn-deficient soils to evaluate the efficiency of rates, methods and time of MnSO₄.H₂ O application for wheat. Manganese sulphate was broadcast and mixed in soils at the rate of 5 to 50kg Mn ha^–1 before seeding and 10 to 40 kg Mn ha^–1 as top dress at 28 days — just before first irrigation. Three sprays of 1% MnSO₄·H₂O unneutralised solutions were applied, the first at 26 days — 2 days before first irrigation and the others afterward at weekly intervals. Both the methods caused a significant and marked increase in grain yield. Three foliar sprays were as effective as soil applications of 20 to 40 Kg Mn ha^–1 before seeding. The difference in grain yield resulting from soil applications of Mn before seeding and applications at the first irrigation was not significant. The DTPA-Mn status of 20 fields, selected on the basis of varying degree of Mn deficiency, was related to grain yield (r = 0.77^**). Also grain yield of all the experiments had a significant correlation with Mn content of grain (r = 0.55^** to 0.82^**) and straw (r = 0.77^** to 0.82^**). The critical limits calculated by statistical method were 1.25, 2.18 and 3.5 mg Mn kg^–1 soil for severe deficiency, deficiency and latent deficiency respectively for wheat.     

Critical levels for soil pH,available P,K, Zn and Mn and maize ear-leaf content of P,Cu and Mn in sedimentary soils of South-Western Nigeria

In the sedimentary soils of South-western Nigeria, actual and expected relative yields of maize were plotted against soil physical factors, soil avalilable nutrients and ear-leaf content of maize. These were used to set critical ranges of these factors for optimum production. Regression equations were obtained for each of the soil and plant factors for predicting yield, thereby making possible yield prediction with levels of each of these factors in these soils if all other factors are constant.The critical range concept combined with the soil physical and chemical properties and plant nutrient content could be a useful diagnostic tool for soil ammendment in crop production. Critical ranges were set as follows:pH, 6–6.5; available P (Bray's Pl), 10–16 mg Kg^–1; Exchangeable K, 0.6–0.8 me K100g^–1; available Zn, 5–10mg kg^–1; available Mn, about 25 mg Kg^–1; Ear-leaf P, 2.5–3.0%; Ear-leaf Cu, 10–20 mg Kg^–1; Earleaf Mn, about 50 mg Kg^–1.     

土壤中蒽、菲、芘对小麦种子的生态毒性效应

采用生物培养实验,研究了土壤中蒽、菲、芘对小麦种子的发芽与根伸长抑制生态毒性.结果表明,三类多环芳烃(PAHs)对小麦种子萌发过程中的生长均有不同程度的影响.其中菲的影响最为明显,菲对小麦根毒害的敏感区间为每千克土样0 mg～400 mg,当每千克土样中含菲400 mg时,小麦根伸长抑制率达到了52%.PAHs生态毒性与其溶解度和结构有关.     

Agronomic and economic evaluation of site-specific nutrient management for irrigated wheat in northwest India

Similar to other regions of Asia, irrigated wheat (Triticum aestivum L.) yield increases in Punjab, India, have slowed in recent years. Future yield increases may occur in smaller increments through fine-tuning of crop management mainly by accounting for the large spatial and temporal variation in soil characteristics. On-farm experiments were conducted from 2002–03 to 2004–05 on 56 irrigated wheat farms (hereafter referred to as ‘sites’) in six key irrigated rice (Oryza sativa L.)-wheat regions of Punjab to evaluate an approach for site-specific nutrient management (SSNM). Site-specific N–P–K applications were calculated by accounting for the indigenous nutrient supply, yield targets, and nutrient demand as a function of the interactions between N, P, and K. The performance of SSNM was tested for two wheat crops. Compared with the current farmers’ fertilizer practice (FFP), average grain yield increased from 4.2 to 4.8 Mg ha⁻¹, while plant N, P, and K accumulations increased by 12–20% with SSNM. The gross return above fertilizer cost (GRF) was about 13% greater with SSNM than with FFP. Improved timing and/or splitting of fertilizer N increased N recovery efficiency from 0.17 kg kg⁻¹ in FFP plots to 0.27 kg kg⁻¹ in SSNM plots. The agronomic N use efficiency was 63% greater with SSNM than with FFP. As defined in our study, SSNM has potential for improving yields and nutrient use efficiency in irrigated wheat. Future research must build on the present approach to develop a more practical way for achieving similar benefits across large areas without site-specific modeling and with minimum crop monitoring.     

Relationship between soil physical and chemical characteristics and ear-leaf concentration of P,K, Mg,Zn, Fe,Cu, Mn and relative yield of maize in soils derived from sedimentary rocks of South-Western Nigeria

In a four-season field experiment conducted in 18 locations covering two different ecological zones of the sedimentary forest soils of South-Western Nigeria, relationships were established by simple correlation between the ear-leaf content of P, K, Mg, Zn, Fe, Cu, Mn, relative yield of maize (RY), soil physical characteristics and soil nutrient status. Soil pH was strongly related to the relative yield, soil clay, available P, exchangeable Ca, K, Zn, and Mn in soils, P and Cu concentration in the ear-leaf.Organic matter did not appear to play a very significant role in nutrient supply or relate to nutrient element concentration in the ear-leaf and relative yield in soils that are relatively low in soil organic matter.Nitrogen was not determined. Phosphorus among all the elements determined seemed to have a high significant effect on Ca, K, Zn, Mn and RY. However, the effect on RY was negative. Manganese in both soil and ear-leaf had the highest negative significant relationship with yield in the zone.The multiple regression analysis indicated a relationship meaning that the soil physical and chemical properties and ear-leaf content of the elements P, K, Mg, Zn, Fe, Cu, Mn are important to maize cultivation in this zone. Hence consideration of a combination of soils and plant factors are essential before meaningful fertilizer recommendation can be made for maize in the zone under study.     

Metal availability in contaminated soils: II. Uptake of Cd, Ni and Zn in rice plants grown under flooded culture with organic matter addition

Higher accumulation of toxic heavy metals in rice grown in contaminated soils may lead to health disorder in humans in tropical countries as rice is a staple diet. A pot experiment was conducted in a growth chamber to investigate the effect of flooding and non-flooding conditions in three soils added with4% organic matter on the concentration and uptake of Cd, Ni and Zn by rice plants (Oryza sativa L.). In flooding condition, the level of standing water was at a height of 2.5 ± 0.5 cm above the soil surface and in non-flooded culture80 ± 5% of water holding capacity was maintained. Flooding condition significantly(p < 0.05) reduced the concentration and uptake of Cd, Ni and Zn in rice grown in all three soils. The overall reduction of metal concentration in shoot at vegetative stage, and straw and polished rice at maturity, under flooding conditions was 84, 89, and 79% for Cd; 21,63and 65% for Ni; and 52, 78 and 16% for Zn, respectively. Organic matter addition significantly reduced the Ni concentration in plant parts but no such reduction was seen for Cd and Zn. Accumulation index of Cd and Zn was 82and 55% higher than that of Ni in the plant and the index of all three metals was higher in the tannery soil than the other two soils. Polished rice contained significantly lower amounts of Cd, Ni and Zn than shoot and straw. Cadmium and Ni uptake in polished rice was > 20% of the total uptake and thus it may be a concern for human health. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effects of input level and crop diversity on soil nitrate-N,extractable P,aggregation, organic C and N,and nutrient balance in the Canadian Prairie

A field experiment was conducted from 1995 to 2006 on a Dark Brown Chernozem (Typic Boroll) loam soil at Scott, Saskatchewan, Canada to determine the influence of input level and crop diversity on accumulation and distribution of nitrate-N and extractable P in the soil profile, and soil pH, dry aggregation, organic C and N, and nutrient balance sheets in the second 6-year rotation cycle (2001–2006). Treatments were combinations of three input levels (organic input under conventional tillage—ORG; reduced input under no-till—RED; and high input under conventional tillage—HIGH), three crop diversities (fallow-based rotations with low crop diversity—LOW; diversified rotations using annual cereal, oilseed and pulse grain crops—DAG; and diversified rotations using annual grain and perennial forage crops—DAP), and six crop phases including green manure (GM), chem-fallow or tilled-fallow (F). Amount of nitrate-N in 0-240 cm soil was usually highest under the HIGH input-LOW crop diversity treatment and lowest under the ORG input-DAP crop diversity treatment. The distribution of nitrate-N in various soil depths suggested downward movement of nitrate-N up to 240 cm depth, especially with LOW crop diversity compared to DAP crop diversity, and with HIGH input. In some years, the ORG input systems had higher nitrate-N than the RED or HIGH input systems, which was attributed to low extractable P in soil for optimum crop growth and reduced nutrient uptake with ORG input management. Extractable P in soil was higher by a small margin for HIGH or RED input relative to ORG input in the 0–15 cm layer, suggesting little downward movement of P. Crop diversity did not affect extractable soil P due to the low baseline levels of P in this soil. The proportion of fine dry aggregates (<1.3 mm, erodible fraction) in 0–5 cm soil was highest with LOW crop diversity-HIGH input system, and lowest with DAG diversity-RED input system. The opposite was true for large aggregates (>12.7 mm). Wet aggregate stability was higher for RED input compared to ORG and HIGH input, which was attributed to the increase in the concentration of organic C in aggregates in the RED input system. Amount of light fraction organic matter (LFOM), light fraction organic C (LFOC) and light fraction organic N (LFON) in 0–15 cm soil was higher for RED input compared to ORG and HIGH inputs, and higher for DAG and DAP crop diversities than for LOW crop diversity. Soil N and P were usually deficient under ORG input management, but large amounts of N and P were unaccounted for, or in surplus, under RED and HIGH inputs, despite a marked increase in plant N and P uptake and crop yield compared to ORG input. Overall, our findings suggest that soil quality can be improved and nutrient accumulation in the soil profile can be minimized by increasing cropping frequency, reducing/eliminating tillage, and using appropriate combinations of fertilizer input and diversified cropping.     

The mycorrhizal fungus Glomus mosseae enhances growth, yield and chemical composition of a durum wheat variety in 10 different soils

The effect of the vesicular arbuscularmycorrhizal fungus (VAMF) Glomus mosseae ongrowth, yield and nutrients' uptake of the durum wheatvariety Sifnos was investigated in ten differentsoils. Inoculation had a positive effect on tillering,improved plant growth up to 11.6 times and increasedgrain yield up to 5.4 times as compared tonon-inoculated plants. The thousand kernels weight wasimproved by up to 60%. The analysis of shoot tissue ofthe mycorrhizal plants showed that P concentration wasincreased up to 4 fold, while the K, Ca and Mg uptakewas similar for both mycorrhizal and non-mycorrhizalplants. The concentrations of the trace elements Mn,Zn, Fe and Cu were lower in the mycorrhizal plantscompared to that of non-inoculated ones. The P and Mgconcentration of the grains produced by the inoculatedplants was increased while the Ca concentration wasdecreased. The concentration of the heavy metals waseither decreased ( Mn, Fe, Co, Cr, Ni, Pb) or remainedunchanged (Zn, Cu). The colonization in the roots ranged from 23 to 78%.     

An isomorphic Peng-Robinson equation for phase-equilibria properties of hydrocarbon mixtures in the critical region

The principle of isomorphism of critical phenomena asserts that the equation of state of fluid mixtures in the critical region has the same form as that of the pure components, provided that the mixture is not considered at a fixed composition but at a fixed value of a constant field variable related to the chemical potentials of the components of the mixtures. This principle has been successfully applied by various investigators to formulate nonclassical equations of state for fluid mixtures in the critical region. In this paper we show how the same principle can be applied to simple classical equations of state using the Peng-Robinson equation as a representative example. The isomorphic Peng-Robinson equation thus obtained is applied to represent phase equilibria properties of some binary mixtures of methane, butane and decane.     

Acidic pretreatment of wheat straw in decanol for the production of surfactant, lignin and glucose

Wheat straw is an abundant residue of agriculture which is increasingly being considered as feedstock for the production of fuels, energy and chemicals. The acidic decanol-based pre-treatment of wheat straw has been investigated in this work. Wheat straw hemicellulose has been efficiently converted during a single step operation into decyl pentoside surfactants and the remaining material has been preserved keeping all its promises as potential feedstock for fuels or value added platform chemicals such as hydroxymethylfurfural (HMF). The enzymatic digestibility of the cellulose contained in the straw residue has been evaluated and the lignin prepared from the material characterized. Wheat-based surfactants thus obtained have exhibited superior surface properties compared to fossil-based polyethoxylates decyl alcohol or alkyl oligoglucosides, some of which are largely used surfactants. In view of the growing importance of renewable resource-based molecules in the chemical industry, this approach may open a new avenue for the conversion of wheat straw into various chemicals.     

Response of wheat to nitrogen fertilization,a data set to validate simulation models for nitrogen dynamics in crop and soil

A data set originating from winter wheat experiments at three locations during two years is described. The purpose is to provide sufficient data for testing simulation models for soil nitrogen dynamics, crop growth and nitrogen uptake. Each experiment comprised three different nitrogen treatments, and observations were made at intervals of two or three weeks. The observations included measurements of soil mineral nitrogen content, soil water content, groundwater table, dry matter production and dry matter distribution, nitrogen uptake, nitrogen distribution and root length density.