WHEAT RESPONSE TO FARM YARD MANURE AND NITROGEN FERTILIZATION UNDER MOISTURE STRESS CONDITIONS

Information on the combined use of organic and inorganic fertilizers on wheat (Triticum aestivum L.) productivity is lacking under moisture stress conditions of Northwest Pakistan. The present experiment was designed to ascertain the combined effect of organic and inorganic fertilizer management on rainfed wheat. Four levels of farm yard manure, FYM, (0, 10, 20, and 30 Mg FYM ha^?1) and nitrogen (0, 30, 60, 90, and 120 kg N ha^?1) were used. The experiment was conducted at the Agriculture Research Farm of NWFP Agricultural University Peshawar, Pakistan during crop season of 2003–04. The experiment was laid out in randomized complete block design with four replications. Plant height, productive tillers m^?2, grains spike^?1, grain yield, straw yield, and harvest index were significantly higher in plots which received 30 Mg FYM ha^?1. In the case of nitrogen (N) no distinctive differences between the effect of 90 and 120 kg ha^?1 was observed for most of the parameters. Nitrogen application at 90 kg ha^?1 had significantly higher; plant height, grains spike^?1, grain yield, straw yield, and harvest index as compared with the lower levels, i.e., 0, 30, and 60 kg N ha^?1 but were at par with 120 N kg ha^?1. Significantly higher numbers of productive tillers m^?2, grains spike^?1, grain yield, straw yield and harvest index were recorded with application of 30 Mg FYM ha^?1 + 90 kg N ha^?1. The present study suggested that application of 30 Mg FYM ha^?1 + 90 kg N ha^?1 are promising levels for higher production of wheat under moisture stress conditions. Further research work is needed to ascertain the effect of N above 90 kg ha^?1 under different moisture regimes.     

Carrier-based and liquid bioinoculants of Azotobacter and PSB saved chemical fertilizers in wheat (Triticum aestivum L.) and enhanced soil biological properties in Mollisols

Abstract

The increasing cost and imbalanced use of chemical fertilizers in wheat (Triticum aestivum L.) stressed the need to explore the potential of bioinoculants of Azotobacter and PSB for saving fertilizer N and P. Field experiments conducted for two years in a Mollisol at Pantnagar revealed maximum plant height, grain and straw yields and nutrient uptake by wheat with application of 100% NP. However, soil application of carrier-based biofertilizer at 10?kg?ha^?1 and liquid-based biofertilizers at 625 and 1250?mL?ha^?1 rates in combination of 75% NP were at par with 100% NP by recording significantly more mean plant height at different intervals, grain yield, by 10.9, 10.5 and 10.8%, and straw yield, by 8.6, 8.2 and 9.1%, over 75% NP, respectively. These treatments also accumulated significantly more N, P and K in plant at different age and; grain and straw. An application of liquid biofertilizer at 1250?mL?ha^?1 with 75% NP gave maximum population of Azotobacter and PSB, microbial biomass C and activities of acid and alkaline phosphatase in soil at different crop age. The carrier and liquid formulations of the biofertilizers were comparable in their performance. Irrespective of formulation and doses, application of biofertilizers in soil was found better than seed treatment for different recorded parameters. An application of 625?mL?ha^?1 liquid biofertilizers in soil with 75% NP was found optimum for the growth, yield and nutrients uptake and soil biological properties.     

Effects of Conventional and Stabilized Urea Fertilizers on Soil Biological Status

Effects of stabilized urea fertilizers [Alzon 46 (A) and UREAstabil (US)] on soil microbiological and chemical parameters and also on grain yield, 1000-grain weight, and oil content were tested in a precise field study on Luvisol in 2010–2012. Winter rapeseed (Brassica napus L. cv. Californium) was fertilized both in autumn [45 kg nitrogen (N) ha^?1] and in spring (155 kg N ha^?1) with A [urea with DCD (dicyandiamide) plus pyrrodiazole (1,2,4-1H-triazole)], US {urea with NBPT [N-(n-butyl)-thiophosphoric acid triamide]}, and conventional N fertilizers (pure urea, calcium ammonium nitrate). Eleven parameters were used to evaluate the soil status: microbial biomass carbon (C; microwave method [MW]), dehydrogenase activity, arylsulfatase activity, available organic carbon, electroconductivity, C_org (MW method), and pH (in water, H₂O). None of the 11 parameters demonstrated significant difference between control, conventional N fertilizers, and stabilized urea fertilizers. The greatest yield significantly different from the control (zero kg N ha^?1; 2598 ± 881 kg ha^?1) was found for both stabilized urea fertilizers: A (200 kg N ha^?1; 3772 ± 759 kg ha^?1) and US (200 kg N ha^?1; 3764 ± 625 kg ha^?1). The control achieved the greatest oil content (46.0 ± 1.2%), which was significantly different from all N-fertilized variants, and also the greatest 1000-grain weight (5.62 ± 0.62 g).     

Economic and environmental optimization of nitrogen fertilizer recommendations for cereals in Norway

Abstract

Results of 240 annual N fertilizer trials in 1991–2007 in spring and winter cereals are presented. On average, spring barley and oat yields increased little beyond 120 kg N ha^?1 in fertilizer. Somewhat higher figures were found for spring and winter wheat. Regression equations for yield and N uptakes in grain and straw were derived, related to N fertilizer input and the yield level in individual trials (indicator of yield expectancy). These equations accounted for 90% of the variation in yield and 80% of that in N uptake. Quadratic N responses were significant in all cases, as were interactions between N responses and yield level. They were verified with data from 27 separate trials performed in 2008–2010. The yield equations were used to calculate economically optimum N fertilizer levels with varying ratios of product price to fertilizer cost at contrasting levels of yield. The optimum N fertilizer level for barley and oats was found to increase by 8.3 kg N ha^?1 per Mg increase in expected yield. The equivalent figure in wheat was 16.3 kg N ha^?1. Optimum N fertilizer levels decreased by 4.1 and 6.7 kg N ha^?1, for barley/oats and wheat respectively, per unit increase in the cost/price ratio. The equations for N uptake were used to calculate simple N balances between fertilizer input and removal in crop products. Large N surpluses were indicated at low levels of yield expectancy, but the surplus declined markedly with increasing yield level, despite greater N fertilizer inputs at high yield. Calculations made for national average yield levels in recent years showed N surpluses of 50–60 kg N ha^?1 when only grain is removed and 25–40 kg N ha^?1 when straw is removed also. Limiting N input to obtain zero balance reduces yields considerably at average levels of yield expectancy.     

Nitrogen source and application method impact on corn yield and nutrient uptake

Farmers are looking for better management practices to utilize animal manure as an alternative to chemical fertilizers. A 2-year field experiment was conducted to study the effects of nitrogen (N) fertilizer source and application methods to Nicholson silt loam soil in central Kentucky, USA for no-till corn (Zea mays) production. The region has a temperate climate with a mean temperature of 14.5°C and rainfall of 1300 mm year^?1. Treatments included a control, 179 kg N ha^?1 urea ammonium nitrate (UAN) applied as preplant and sidedress, and swine effluent that was applied by three methods: broadcast, injection, and Aerway. Injection method produced the greatest corn grain yield (11.88 Mg ha^?1) and biomass yield (18.9 Mg ha^?1) in 2007. Results demonstrated that the effluent application methods and the timing of UAN application may not be agronomically important for corn production in this region. Hence, more studies are needed on different soils in this region.     

Influence of nitrogen and weed management on the productivity of upland rice

Nitrogen and weeds are two important factors that influence the productivity of rainfed upland rice (Oryza sativa L.) in tropical Asia. A low recovery of applied fertilizer N in rainfed uplands is generally associated with high nitrate leaching losses and weed interferences. Field experiments were conducted during the wet seasons of 2002 and 2003 at the research farm of Central Rainfed Upland Rice Research Station, Hazaribag, Jharkhand, India, to determine the response of upland rice to nitrogen applied at 60 kg N ha^–1 as different forms of urea (single pre‐plant application of controlled‐release urea, single pre‐plant application of urea supergranules, and split application of prilled urea with or without basal N) against no N application under three weed‐control regimes (unweeded, pre‐emergence application of butachlor at 1.5 kg a.i. ha^–1 supplemented with one single hand weeding or two hand weedings). The response of rice to applied N varied greatly among the three weed‐control regimes. Across the different N treatments, the application of 60 kg N ha^–1 resulted in a grain‐yield increase above the unfertilized control of only 0.24 Mg ha^–1 in unweeded treatments, whereas yields increased by 1.07 Mg ha^–1 when butachlor application was supplemented with a single hand weeding and by 1.28 Mg ha^–1 with two hand weedings. Among the weed‐control measures, hand weeding twice produced highest grain yield in both years. The comparison of different forms of urea showed that a single pre‐plant application of controlled‐release urea resulted in average grain yields of 1.57 and 1.87 Mg ha^–1 compared to 1.32 and 1.30 Mg ha^–1 in the case of the recommended practice of split‐applied prilled urea in the years 2002 and 2003, respectively. The highest agronomic N use efficiency of 15–20 kg grain per kg N applied and the highest apparent N recovery of 39%–45% were attained with controlled‐release urea, suggesting that this N form is particularly beneficial for upland‐rice cultivation under variable rainfall conditions, provided weeds are controlled.     

Influence of Long-term Tillage,Straw, and N Fertilizer Management on Crop Yield,N Uptake,and N Balance Sheet in Two Contrasting Soil Types

Field experiments (established in autumn 1979, with monoculture barley from 1980 to 1990 and barley/wheat–canola–triticale–pea rotation from 1991 to 2008) were conducted on two contrasting soil types (Gray Luvisol [Typic Haplocryalf] loam soil at Breton; Black Chernozem [Albic Agricryoll] silty clay loam soil at Ellerslie) in north-central Alberta, Canada, to determine the influence of tillage (zero tillage and conventional tillage), straw management (straw removed [S_Rem] and straw retained [S_Ret]), and N fertilizer rate (0, 50 and 100 kg N ha^?1in S_Ret, and only 0 kg N ha^?1in S_Rem plots) on seed yield, straw yield, total N uptake in seed + straw (1991–2008), and N balance sheet (1980–2008). The N fertilizer urea was midrow-banded under both tillage systems in the 1991 to 2008 period. There was a considerable increase in seed yield, straw yield, and total N uptake in seed + straw with increasing N rate up to 100 kg N ha^?1 under both tillage systems. On the average, conventional tillage produced greater seed yield (by 279 kg ha^?1), straw yield (by 252 kg ha^?1), and total N uptake in seed + straw (by 6.0 kg N ha^?1) than zero tillage, but the differences were greater at Breton than Ellerslie. Compared to straw removal treatment, seed yield, straw yield, and total N uptake in seed + straw tended to be greater with straw retained at the zero-N rate used in the study. The amounts of applied N unaccounted for over the 1980 to 2008 period ranged from 1114 to 1846 kg N ha^?1 at Breton and 845 to 1665 kg N ha^?1 at Ellerslie, suggesting a great potential for N loss from the soil-plant system through denitrification, and N immobilization from the soil mineral N pool. In conclusion, crop yield and N uptake were lower under zero tillage than conventional, and long-term retention of straw suggests some gradual improvement in soil productivity.     

Effects of controlled-release urea combined with conventional urea on nitrogen uptake,root yield,and quality of Platycodon grandiflorum

Field experiments were conducted with four nitrogen fertilizer treatments to study the effects of controlled-release urea combined with conventional urea on the nitrogen uptake, root yield, and contents of protein, soluble sugar, saponin, zinc (Zn), iron (Fe), magnesium (Mg), and copper (Cu) in Platycodon grandiflorum. Field experiments were conducted with four nitrogen (N) fertilizer treatments: no N fertilization; conventional urea with N rate of 175 kg N ha^?1; conventional urea with N rate of 160 kg N ha^?1; controlled-release urea combined with conventional urea with N rate of 160 kg N ha^?1; controlled-release urea combined with conventional urea with N rate of 135 kg N ha^?1. The results showed that nitrogen application significantly increased the yield of P. grandiflorum compared with the control. Treatment with controlled-release urea combined with conventional urea at 160 kg N ha^?1 provided the highest yield of 7329.58 kg ha^?1. Nitrogen application also increased the contents of soluble sugar, total saponin, protein, Zn, Fe, and Mg but decreased Cu content. Protein, saponin, and Zn contents were significantly higher, but Cu content was lower in P. grandiflorum fertilized with controlled-release urea combined with conventional urea than those fertilized with conventional urea alone. The combination of controlled-release urea with conventional urea at 160 kg N ha^?1 was the optimal treatment under the experimental condition investigated in this study.     

Maize (Zea mays L.) Grain Yield Response to Methods of Nitrogen Fertilization

ABSTRACT

In the developing world, fertilizer application is commonly achieved by broadcasting nutrients to the soil surface without incorporation. A commonly used nitrogen (N) source is urea and if not incorporated, can sustain N losses via ammonia volatilization and lower crop yields. This study evaluated the effect of planting, N rate and application methods on maize (Zea mays L.) grain yield. An experiment with a randomized complete block design (nine treatments and three replications) was established in 2013 and 2018 in Oklahoma. The planting methods included; farmer practice (FP), Oklahoma State University hand planter (OSU-HP), and John Deere (JD) mechanical planter. Side-dress N application methods included; dribble surface band (DSB), broadcast (BR), and OSU-HP. Nitrogen was applied at the rate of 30 and 60 kg ha^?1 as urea and UAN at V8 growth stage. On average, planting and applying N at 60 kg ha^?1 using OSU-HP resulted in the highest yield (11.4 Mg ha^?1). This exceeded check plot yield (5.59 Mg ha^?1) by 104%. Nitrogen application improved grain yield by over 57% when compared to the 0-N check (8.77 Mg ha^?1). Mid-season N placement below the soil surface using OSU-HP makes it a suitable alternative to improve grain yield.     

EFFECTS OF A MULTISTRAIN BIOFERTILIZER AND PHOSPHORUS RATES ON NUTRITION AND GRAIN YIELD OF PADDY RICE ON A SANDY SOIL IN SOUTHERN VIETNAM

Field experiments during two successive rainy seasons were conducted in southern Vietnam to evaluate the effects of a commercial inoculant biofertilizer (‘BioGro’) and fused magnesium phosphate (FMP) fertilizer on yield and nitrogen (N) and phosphorus (P) nutrition of rice. Inoculation with BioGro containing a pseudomonad, two bacilli and a soil yeast significantly increased grain yield in the second season and straw yield in both seasons by 3–5%. The FMP fertilizer significantly increased grain yield from 1.72–2.33 t ha^?1 to 2.99–3.58 t ha^?1 along with total N and P accumulation at all rates in both cropping seasons. In the first season the difference in grain yield between BioGro treated and untreated plots was marginal but in the second season BioGro out-yielded the control at all the rates of added P. Overall, BioGro application did not compensate for low P fertilizer application to the same extent previously demonstrated for low N fertilizer applications.     

Rice productivity and profitability with slow-release urea containing organic-inorganic matrix materials

Applying slow-release fertilizers is possible means for reducing nitrogen(N) loss in rice production. Matrix-based fertilizers represent novel slow-release fertilizers. To date, there is little consensus about the effect of combined addition of organic and inorganic matrix materials on rice production. We developed a slow-release urea fertilizer with selected organic and inorganic matrix materials. The study aimed to: i) determine the effect of the slow-release urea on rice yield, profit, and agronomic efficiency and ii) elucidate its possible mechanisms. A two-year field experiment was conducted during 2015–2016. Besides,laboratory experiments were conducted to determine the potential N loss risk. Three treatments were set up: control without N application(CK), regular urea treatment(RU, 150 kg N ha~(-1)), and slow-release urea treatment(SU, 150 kg N ha~(-1)). The results showed that rice biomass and grain yield were significantly higher in SU than in RU(P 0.05). The higher panicle density in SU was largely responsible for the greater grain yield. Net profit in SU was US$450 ha~(-1), higher than in RU. Agronomic efficiency was significantly greater in SU than in RU(P 0.05). Rice height, root area, leaf chlorophyll, leaf nitrate reductase activity, and leaf glutamine synthetase activity were larger in SU than in RU. Less N loss and greater soil N availability were partly responsible for the improvements in rice growth traits and physiological parameters in SU. Overall, the slow-release urea is a promising fertilizer for rice production.     

EFFECTIVENESS OF SEEDROW-PLACED N WITH POLYMER-COATED AND NBPT-TREATED UREA FOR CANOLA AND WHEAT

Seedrow-placed urea minimizes soil disturbance in reduced tillage systems, but it generally decreases seedling emergence (or stand density) at nitrogen (N) rates adequate for optimum crop yield. Two three-year field experiments were conducted on canola (Brassica napus L.) and spring wheat (Triticum turgidum L.) at Melfort Research Farm, Saskatchewan, Canada, to determine the influence of N rate (40, 80 and 120 kg N ha^?1), N source [untreated urea (urea), polymer-coated urea (ESN), and urea treated with Dicyandiamide (DCD) and N-(n-butyl) thiophosphoric triamide (NBPT or Agrotain^TM) (SuperU) in 2007, or NBPT only (AgrotainU) in 2008 and 2009], and placement (side-banded N and seedrow-placed N, using knives to create 2 cm wide band), plus a zero-N control, on seedling emergence, seed and straw yield, protein concentration (PC) in seed, and N uptake in seed and straw. For both crops, side-banded N had no detrimental effect on seedling emergence compared to the zero-N control for all rates and sources. Seedrow-placed ESN had little or no effect on seedling emergence of wheat or canola. Conversely, seedrow-placed urea, SuperU or AgrotainU reduced seedling emergence for wheat at the 80 and 120 kg N ha^?1 rates and reduced canola seedling emergence substantially at all rates, but particularly at the 80 and 120 kg N ha^?1. Seed yield and N uptake were generally greater with ESN than urea and also SuperU or AgrotainU, when the fertilizers were seedrow-placed at high N rates. The findings suggest the effectiveness of ESN in providing greater seedrow-placed N application options for producers.     

Inoculation of rapeseed under different rates of inorganic nitrogen and sulfur fertilizer: impact on water relations,cell membrane stability,chlorophyll content and yield

It is important to develop integrated fertilization strategies for various crops that enhance the competitive ability of the crop, maximize crop production and reduce the risk of nonpoint source pollution from fertilizers. In order to study the effects of mineral nitrogen fertilization and biofertilizer inoculation on yield and some physiological traits of rapeseed (Brassica napus L.) under different levels of sulfur fertilizer, field experiments in factorial scheme based on randomized complete block design were conducted with three replications in 2012 and 2013. Experimental factors were: (1) four levels of chemical nitrogen fertilizer (0, 100, 150 and 200 kg N ha^?1), (2) two levels of biofertilizer (with and without inoculation) consisting Azotobacter sp. and Azospirillum sp. and (3) two levels of sulfur application (0 and 50 kg S ha^?1). Rapeseed yield, oil content of grains and studied physiological traits had a strong association with the N fertilization, biofertilizer inoculation and sulfur (S) application. Higher rates of N fertilization, biofertilizer inoculation and S application increased the grain yield of rapeseed. In the case of physiological traits, the highest value of relative water content (RWC) was recorded in 100 kg N ha^?1 that was statistically in par with 150 kg N ha^?1 application, while usage of 150 kg N ha^?1 showed the maximum cell membrane stability (CMS). Inoculation with biofertilizer and S fertilization resulted in higher RWC and CMS in rapeseed plants. The chlorophyll content showed its maximum values in the highest level of N fertilization, biofertilizer inoculation and S application. The usage of 200 kg N ha^?1 significantly decreased the oil content of rapeseed grains, but the highest grain oil content was obtained from the application of 150 kg N ha^?1, Azotobacter sp. and Azospirillum sp. inoculation and S fertilization. It seems that moderate N rate (about 150 kg N ha^?1) and S application (about 50 kg S ha^?1) can prove to be beneficial in improving growth, development and total yield of inoculated rapeseed plants.     

Study on the Effects of Organic and Inorganic Nitrogen Fertilizer on Yield,Yield Components,and Nodulation State of Chickpea (Cicer arietinum L.)

To study the effects of organic and inorganic nitrogen (N) on yield and nodulation of chickpea (Cicer arietinum L.) cv. ILC 482, a spilt-plot experiment based on randomized complete block design with four replications was conducted in 2008 at the experimental farm of the Agriculture Faculty, University of Mohaghegh, Ardabili. Experimental factors were inorganic N fertilizer at four levels (0, 50, 75, and 100 kg ha^?1) in the main plots that applied in the urea form, and two levels of inoculation with Rhizobium bacteria (with and without inoculation) as subplots. Nitrogen application and Rh. inoculation continued to have positive effects on yield and its attributes. The greatest plant height, number of primary and secondary branches, number of pods per plant, number of filled and unfilled pods per plant, number of grains per plant, grain yield, and biological yield were obtained from the greatest level of N fertilizer (100 kg urea ha^?1) and Rh. inoculation. Application of 75 and 100 kg ha^?1 urea showed no significant difference in these traits. Furthermore, the greatest rate of N usage (100 kg urea ha^?1) adversely inhibited nodulation of chickpea. Number and dry weight of nodules per plant decreased significantly with increasing N application rate. The lowest values of these traits recorded in application of 100 kg ha^?1 urea. Results indicated that application of suitable amounts of N fertilizer (i.e., between 50 and 75 kg urea ha^?1) as starter can be beneficial to improve nodulation, growth, and final yield of inoculated chickpea plants.     

Efficacy of starter N fertilizer and rhizobia inoculant in dry pea (Pisum sativum Linn.) production in a semi-arid temperate environment

ABSTRACT

Uncertainties exist about the importance of rhizobia inoculant and starter nitrogen (N) application in dry pea (Pisum sativum L.) production. Three field experiments were conducted to evaluate how rhizobia inoculant and starter N fertilizer affect pea seed yield and protein concentration in a semi-arid environment in central Montana. Commercial rhizobia inoculant was mixed with seed prior to planting at the manufacturer’s recommended rate. Starter N fertilizers were applied into the same furrow as seed at 0, 22, 44 and 88 kg ha^?1 as urea, slow-release polymer-coated N fertilizer (ESN), and a combination of both. The application of rhizobia inoculant had no or a very small beneficial effect on pea yield in lands with a previous history of peas. In a land without pea history, application of rhizobia increased pea seed yield by 16%. The positive effect of starter N was only pronounced when initial soil N was low (≤ 10 kg ha^?1 nitrate-nitrogen), which increased net return by up to US$ 42 ha^?1. In this condition, application of slow-release N outperformed urea. However, application of starter N (especially with urea) had a negative effect on pea establishment, vigor and seed yield when soil initial N was high (≥ 44 kg ha^?1 NO₃-N). The results indicate that the rate, placement and form of the starter N must be optimized to benefit pea yield and protein without detrimental effects on germination and nodulation. Moreover, application of starter N must be guided by the soil nitrate content.     

Impact of urea and farm yard manure on nitrate concentration in soil profile and productivity of wheat crop

Abstract

During the last century, concerns about nitrate presence in the groundwater have tremendously increased worldwide, mainly because of its detrimental consequences on environment and human health. There are different factors contributing their past in nitrate pollution, farm manure is given due consideration. Knowing above facts, a field study was performed to check the effect of different farm yard manure (FYM) levels with urea on nitrate distribution in the soil profile and yield of wheat crop. The experiment was set out in a randomized complete block design, consisted of application of nitrogen at 125?kg ha^?1 from urea, 80?kg ha^?1 of N from urea +10 tons FYM ha^?1 and 20 tons FYM ha^?1 with three replications. Wheat (cultivar S7ehar-2006) was sown as test crop. Soil samples were examined to measure the nitrate concentration from four different depths (0–25, 25–50, 50–75, and 75–100?cm) after harvesting. Results showed that the straw yield, total biomass, spike length, and number of grains per spike and 1000-grain weight were significantly influenced by fertilizer strategies. All manure treatments significantly affected the infiltration rate and concentration of nitrate at different depths of the soil profile. Farm yard manure showed greater nitrate concentration up to 50?cm depth as compared to alone urea and combined application, while at the depth of 100?cm, combined application of urea and FYM showed a minimum concentration of nitrates than alone application of either urea or FYM.     

Comparative Efficiency of Nitrogen Sources for Lowland Rice Production

Rice (Oryza sativa L.) is the staple food for more than 50% world population and nitrogen (N) is one of the most yield-limiting nutrients for rice production worldwide. A greenhouse experiment was conducted to evaluate the efficiency of three N sources for lowland rice production. The N sources used were ammonium sulfate, common urea, and polymer-coated urea. There were three N rates, i.e. 100, 200, and 400 mg N kg^?1 applied with three sources plus one control treatment (0 mg N kg^?1). Growth, yield, and yield components were significantly increased either in a linear or quadratic fashion with the addition of N fertilizers in the range of 0–400 mg kg^?1 soil. Maximum grain yield was obtained with the addition of ammonium sulfate at 100, 200, and 400 mg kg^?1 of soil. Common urea and polymer-coated urea were more or less similar in grain production at 100 and 200 mg N kg^?1. However, at 400 mg N kg^?1 treatments, polymer-coated urea produced the lowest grain yield. Most of the growth and yield components were positively related to grain yield, except spikelet sterility which was negatively related to grain yield. Nitrogen use efficiency decreased with increasing N rate in all the three N sources. Maximum N use efficiency was obtained with the addition of ammonium sulfate at lower as well as at higher N rates compared with other two N sources.     

Evaluation of Compost for Use as a Soil Amendment in Corn and Soybean Production

The purpose of this research project was to 1) evaluate rate of compost application and 2) to compare compost with uncomposted raw material and inorganic fertilizer N application upon maize and soybean growth and productivity, and upon soil characteristics. During the first three years of the study, the source of uncomposted material and compost was food waste and ground newsprint. During years 4 to 9 of the study, the source of uncomposted material and compost was dairy cow manure and wood chips. Application rates in field site 1 were 0, 11.2, 22.4, 33.6 and 44.8 Mg ha^?1 compost, 44.8 Mg ha^?1 uncomposted material and 140 kg ha^?1 fertilizer N (as urea). Application rates in field site 2 were 0, 22.4, 44.8, 67.2 and 134.4 Mg ha^?1 compost, 134.4 Mg ha^?1 uncomposted manure and 180 kg ha^?1 fertilizer N (dry matter basis). The high rates of compost application significantly raised organic matter levels, and available P and K compared to inorganic fertilizer N. Uncomposted manure and increasing compost application rates significantly increased grain yield, number of kernels per plant and plant weight. Composting significantly reduced pathogen indicator bacteria concentrations. The data of this study suggest that on these high organic matter soils 22.4 Mg ha^?1 to 44.8 Mg ha^?1 are optimal compost application rates.     

Assessment of slow release fertilizers and nitrification inhibitors in flooded rice

This work evaluates the effect of different slow-release fertilizers and nitrification inhibitors (NI) on N-use efficiency, grain yield and N₂ fixation in rice fields of Valencia (Spain) during three consecutive crop seasons (1998–2000). Eight N sources [ammonium sulphate, urea, polymer-coated urea (PCU 32% and 40% N), sulphur coated urea, isobutylidene diurea (IBDU), ammonium sulphate nitrate (ASN) plus dicyandiamide and ASN plus dimethyl pyrazole phosphate, were applied at 120 kg N ha^–1 and at 2 or 15 days before flooding (DBF) during 1998. Another experiment was based on the use of urea blended with PCU (40% N) at four ratios (1:0, 3:1, 1:1, 1:3) and applied at 15 DBF and at four rates (70, 95, 120 and 145 kg N ha-1) during 1999 and at only one rate (120 kg N ha^–1) during 2000. Both experiments also included a control (no N). The results showed that, when applied shortly before flooding, PCU (32% and 40% N) and IBDU application improved biological N₂ fixation compared to the conventional fertilizer application, with or without NI, reaching similar values to those observed in the absence of N fertilizer. Slow release fertilizers, particularly PCU 40% N applied basally before flooding, were the best N source for grain yield and improved recovery efficiency. Differences among N sources were only significant when the flooding was delayed for 15 days after fertilizer application.     

Effect of zinc application methods on apparent utilization efficiency of zinc and potassium fertilizers under rice-wheat rotation

Apparent utilization of zinc (Zn) and potassium (K) fertilizers was examined in rice (Oryza sativa L.)-wheat (Triticum aestivum L.) using combinations of no K; soil applied K levels and no Zn; soil and foliar applied Zn. Application of 33.2 kg K ha^?1 in rice and 24.9 kg K ha^?1 in wheat along with foliar spray of 2 kg Zn ha^?1 at 30 and 60 days gave the highest mean grain yields. Foliar application of zinc increased Zn concentration in flag leaves, grain, and straw of rice and wheat and K concentration in flag leaves of rice and straw of wheat significantly. Potassium application increased Zn concentration in rice grain and straw and K concentration in wheat straw significantly. Zinc and K increased the uptake of each other in grain; straw and total uptake by both crops significantly. Zinc fertilizer enhanced the utilization of soil K. Potassium fertilizer enhanced the utilization of applied Zn.