Early Supplies of Available Nitrogen to Seed‐Row of a Canola Crop as Affected by Fertilizer Placement

Abstract

A field experiment was conducted at Star City (legal location SW6‐45‐16‐W2); Saskatchewan, Canada from May 2000 to June 2000, to measure nitrogen (N) and phosphorus (P) supply rates from fertilizer bands to the seed‐row of canola crop. Ion exchange resin membrane probes (PRS^TM) were used to measure N and P supply rates in four treatments [80 kg N ha^?1 of urea as side‐row band, 80 kg N ha^?1 of urea as mid‐row band, check/no N (side‐row)/P side‐row, check/no N (mid‐row)/seed placed P]. The treatments were arranged in a randomized complete block design with four replications. Two anion and cation exchange resin probes (PRS^TM) were placed in each plot in the seed‐row immediately after seeding and fertilizing. The probes were allowed to remain in the field for 2 days and replaced with another set of probes every 4 days for a total of 14 days until canola emerged. Ammonium‐N, nitrate‐N and P supply rates were calculated based on the ion accumulated on the probes. Urea side‐row band treatments (fertilizer N 2.5 cm to side of every seed‐row) had significantly higher cumulative available N supply rates than mid‐row band placement in which fertilizer N was placed 10 cm from the seed‐row in between every second seed‐row. No significant differences were observed in P supply rates. The higher N rates (120 kg N ha^?1) resulted in lower grain yield in side‐row banding than mid‐row banding possibly due to seedling damage. However, the earlier fluxes of N into the seed‐row observed with side‐row banding may be an advantage at lower N rates in N deficient soils.     

Effect of time of application and amount of nitrogen fertilizer on seed yield and concentration of oil in canola (Brassica napus)

The seed (grain) yield increases (responses) and concentration of oil in seed responses of canola (Brassica napus L.) to applications of fertilizer nitrogen (N), as urea (46% N), was measured in eight field experiments in south-western Australia (SWA). Nitrogen was applied at five different times of application, either at sowing or at three to four weekly intervals until 12–16 weeks (0, 3, 6, 9, 12 or 0, 4, 8, 12, 16) after seedling emergence. Canola, sown in late May to early June, was grown on a range of soil types in different locations of SWA. The greater the amount of N applied and the closer N was applied to the sowing of the canola seed usually gave the largest seed yield increase at both higher rainfall sites (> 500 mm) and lower rainfall sites (<350 mm). Maximum seed yield of canola were reached within nine weeks after seedling emergence. The exception was for a sandy soil (Fluventic Lithic Xerochrept; Brown Tenosol) at Narrogin where applications of N at six, nine, or 12 weeks after emergence gave higher yields compared to N applied earlier mainly due to N leaching in June and July.

The amount of N required for 90% of maximum seed (N_90%Y) yield ranged from five to 58 kg N ha^?1 with the amount depended on location and growing season. For six of the eight sites the higher amounts of N for N_90%Y were required at sowing and three weeks after emergence. Similarly, N use efficiency (NUE, kg grain produced kg N applied^?1) tended was highest for either the N applied at sowing or within three to four weeks after emergence of seedlings. The exception was for a sandy soil at Narrogin where applications of N at six, nine, or 12 weeks after emergence gave higher NUE compared to N applied earlier. N use efficiency decreased as the amount of N increased for all times of N application. Generally, the amount of N applied decreased the oil concentration of canola seed at each time of application. However, the effect of the time of application of N fertilizer on the decrease in oil concentration of canola seed was largest with the highest N level applied at 12 or 16 weeks after seedling emergence. The percentage the oil concentrations decreased as the amount of N applied increased varied with location and growing season. Further research work is required to elucidate the interaction between the growing season, possible rainfall and temperature, and the effects of N on grain yield and oil concentration in seed.     

Effect of Seed-Row Placement of Conventional and Polymer-Coated Urea on Winter Wheat Emergence

Polymer-coated urea (PCU) may facilitate nitrogen (N) placement with the seed. Laboratory experiments evaluated the effect of (i) variety and N treatment and (ii) urea contact with the seed on winter wheat (Triticum aestivum L.) emergence. Four varieties were grown in a silt loam soil (–200 kPa Ψ_m, where Ψ_m is matric potential) with control (0 kg N ha^?1), PCU treatment (44% N) at 56, 112, and 168 kg N ha^?1, or urea treatment (56 kg N ha^?1) placed with the seed. One variety had less emergence than the control with PCU at N rates ≥112 kg ha^?1. Urea delayed and decreased emergence of all varieties. In another experiment, urea (56 kg N ha^?1) was placed in contact with or between seeds. The contact treatment exhibited delayed and lower emergence. The no-contact treatment behaved similar to controls. Large amounts of 44% N PCU can be placed with the seed without reducing wheat emergence when soil Ψ_m is at least –200 kPa.     

Nitrous Oxide Emissions in Response to ESN and Urea Application in a No-Till Barley Cropping System

We investigated the effect of environmentally smart nitrogen (ESN) fertilizer on nitrous oxide (N₂O) emissions under no-till barley (Hordeum vulgare L.) production over 3 years at three sites in Alberta, Canada. Treatments included two barley cultivars, with ESN and urea applied at 1× and 1.5× the recommended rate, and herbicide at 50% and 100% of registered in-crop rates. Cumulative N₂O emissions over the growing season were low (0.11 to 1.32 kg nitrogen (N) per hectare or 0.05–0.22 g N kg^?1 grain yield), and not affected by barley cultivars or herbicide rates in all nine site-years, nor by fertilizer type or rate in seven out of nine site-years. However, average N₂O emissions from ESN were 15% lower (P = 0.05) than urea across all site-years. Our results suggest ESN could play a role in reducing N₂O emissions, but the reduction will depend on rainfall events and crop N utilization.     

Cultivars of canola respond similarly to applied nitrogen in n-deficient soils of south Western Australia

Six cultivars of canola (Brassica napus L.) were grown with six levels of applied nitrogen (N) fertilizer (urea 46% N) at six locations in south Western Australia (SWA) during 2010 and 2011. The aim of the experiment was to determine if the seed yield (SY) increase (response) of the canola and associated herbicide technologies were different to applied N. Open pollinated (OP) and hybrid cultivars of associated herbicide technologies (Triazine Tolerant, TT; Roundup Ready, RR; Clearfield, CL) were used. Varieties had large SY differences with no N applied. Generally, RR hybrid of 2011 tended to have the highest SY, except for Katanning 2011 where several varieties obtained the same SY. The average amount of N required for 90% of the maximum SY was 113 kg N ha^?1 and economic breakeven N rates were less than or equal to 100 kg applied N ha^?1. The average rate of return on investment in fertilizer N was $1.60.

In four out of six experiments RR hybrids had the highest oil concentration with no applied N. N decreased the oil concentration in all canola types, except at Gibson 2010. At Gibson in 2010, N application increased the oil concentration to about 100 kg N ha^?1 with further additions of N decreasing the oil concentration. There was a linear relationship where N application decreased the oil concentration and increased protein concentration of the seed. In this study, the summation of oil percentage and protein concentration in the seed was on average 65%, with RR hybrids producing 67%.

In most aspects, RR hybrids outperformed RR, OP and other canola types; however, hybrid TT and hybrid CL canola did not consistently outperform their OP counterpart. We suggest that current N fertilizer recommendation models are useful for all canola types currently grown in SWA; however, adjustments should be made to take into account the higher SY and oil concentration potential of RR hybrids compared to TT canola at every rate of applied N.     

Lentil Response to Nitrogen Application and Rhizobia Inoculation

Lentils (Lens culinaris L.) are an important component of the dryland farming systems in the western USA. Optimum nitrogen (N) management can enhance yield and quality of lentils. We conducted a field (at two locations, one with previous history of lentil and the other one without lentil history) and a greenhouse study to evaluate response of lentil to the application of rhizobium inoculant and starter N (control, 22 kg N ha^?1 in the form of urea [U], 22 kg N ha^?1 in the form of slow-release or environmentally safe nitrogen [ESN], and 22 kg N ha^?1 U + 22 kg N ha^?1 ESN). In both, the field and the laboratory studies, lentil yield did not respond positively to the experimental treatments. Lentil average yield was 1216 and 1420 kg ha^?1 at the field condition. In this rain-fed system, lentil yield was mainly limited by moisture availability, and the application of an external N did not contribute to the yield enhancement. Both of these treatments, however, increased protein content. Compared to the control, the application of rhizobium plus U and ESN enhanced protein content by about 34% (from 23.1 to 30.9%). The application of U+ESN also considerably increased postharvest residual nitrate (NO₃)-N in the soil, which can be easily leached and creates environmental pollution. Briefly, the application of U+ESN increases lentil protein content, but more efforts are needed to optimize N management in lentils in order to reduce the environmental concerns in the shallow soil.     

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.     

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.     

INFLUENCE OF NITROGEN AND SULFUR ON YIELD AND SEED QUALITY OF THREE CANOLA CULTIVARS

In order to investigate the effect of nitrogen (N) and sulfur (S) fertilizers on yield and seed quality of three canola cultivars, a factorial based on randomized complete block experiment was conducted during 2005–2006 in Iran. Treatments included four nitrogen rates (0, 75, 150, and 225 kg N ha^?1 source of urea), four sulfur rates (0, 100, 200, and 300 kg S ha^?1), and three cultivars (‘Pf’, ‘Option-500’, and ‘Hyola-401’). Results indicated cultivar had a significant effect on all studied traits. ‘Option-500’ and ‘Hyola-401’ cultivars had the highest seed yield, protein content, and N:S ratio in seed. The levels of 150 and 220 kg N ha^?1 resulted in the maximum protein content. Increasing N levels resulted in N content and decreased the oil content. The interaction effect between S and N levels showed the highest N content in seed was obtained with 300 kg S ha^?1 and 225 kg N ha^?1.     

INFLUENCE OF HIGH TEMPERATURE AND UREA FERTILIZATION WITH N-(N-BUTYL) THIOPHOSPHORIC TRIAMIDE AND DICYANDIAMINDE ON COTTON GROWTH AND PHYSIOLOGY

The objective of this growth chamber study was to evaluate the effect of adding N-(n-butyl) thiophosphoric triamide (NBPT) and dicyandiaminde (DCD) to urea fertilizer, on the physiology and growth of cotton (Gossypiumhirsutum L.) under normal and high temperatures. Treatments consisted of two day temperature regimes, 30°C and 38°C, and five nitrogen fertilization applications: unfertilized control, 125 kg ha^?1 of urea, 93 kg ha^?1 of urea, 93 kg ha^?1 urea + NBPT, and 93 kg ha^?1 urea + NBPT + DCD. The addition of NBPT to urea fertilizer had positive effects on leaf chlorophyll, leaf area, dry matter, nitrogen (N) uptake, and N use efficiency. The absence of a significant interaction effect indicated that N fertilization was not influenced by temperature. Deficiency of N significantly decreased leaf chlorophyll, increased glutathione reductase, decreased protein and increased leaf nitrate reductase. Physiological changes under high temperature included increased plant N uptake, glutamine synthetase, leaf chlorophyll, protein content, plant height and leaf area were due to high N uptake and utilization.     

Effect of rates and sources of nitrogen on rice yield,nitrogen efficiency,and methane emission from irrigated rice cultivation

The agronomic benefits of manure application to increase rice production have been recognized, but the impact on global change has always been a controversial topic. This study was designed to determine the separate and combined effects of cattle manure (CM) and nitrogen (N) fertilizer on rice yield, N efficiency, and methane (CH₄) emissions from rice cultivation. A pot-scale experiment was conducted with four levels (0, 60, 120, and 180 kg ha^?1) of N from urea and two levels (120 and 180 kg ha^?1) of N from combination of urea and CM (Urea:CM = 60:60 and 60:120). Rice yield and physiological N efficiency were obtained using agronomic measurements. To determine the global warming potential (GWP) of each treatment, CH₄ emissions were measured throughout the rice-growing period. Grain yield (GY) was not significantly different between the treatments of 120 and 180 kg ha^?1 regardless of N source. However, both rates of CM treatments enhanced CH₄ emission and differences in GWP were significant. In conclusion, urea applied at 120 kg N ha^?1 was optimal for rice productivity and environmental impact (EI) despite CM played a crucial role in improving the N efficiency and total N in the soil after harvest.     

NITROGEN FERTILIZER MANAGEMENT FOR IMPROVED GRAIN QUALITY AND YIELD IN WINTER WHEAT IN OKLAHOMA

From 2002 to date, a long-term field experiment has been conducted at Lake Carl Blackwell, Oklahoma, with different rates and times of nitrogen (N) fertilizer application to determine their effect on grain yield, protein and N uptake of winter wheat. Trend analysis for N rates (0, 50, 100, 150 and 200 kg N ha^?1) and orthogonal contrasts for different application times (pre-plant, top-dressed in February and March) were performed. With increasing fertilizer N, wheat grain yield and protein content increased from 2110 kg ha^?1 to 6783 kg ha^?1 and from 8.96 to 17.19%, respectively. For grain yield, protein, and N use efficiency, split applications of N fertilizer were much more efficient than applying all N pre-plant. Large differences in grain yields were noted for different years at the same N rate (range exceeded 5.0 Mg ha^?1) and that illustrated the need for making within-year-specific N rate recommendations.     

Optimizing water,nitrogen and crop density in canola cultivation using response surface methodology and central composite design

Abstract

Optimisation of water and nitrogen use is an effective management tool to conserve resources and reduce environmental pollutions. Response surface methodology (RSM) is defined as a collection of mathematical and statistical methods that are used to develop, to improve or to optimize a product or process. In order to determine optimum levels of water, nitrogen and planting density of canola (Brassica napus L.), a 2-year experiment (2010–2011) was carried out by central composite design as RSM at the research station of Ferdowsi University of Mashhad. The treatments were designed based on low and high levels of irrigation (1500 and 4000 m³ ha^?1), nitrogen (0 and 400 kg N ha^?1) and density (50 and 150 plant m^?2) as independent variables. Furthermore, seed yield, nitrogen losses, nitrogen use efficiency (NUE) and water use efficiency (WUE) were measured as response variables in a full quadratic polynomial model. Optimum levels of irrigation, nitrogen and planting density were suggested to achieve the target range of dependent variables based on three scenarios: economic, environmental and eco-environmental. The results showed that increasing irrigation and fertilizer led to an increase in seed yield and nitrogen losses, whereas increasing canola density resulted in an increase in seed yield but a decrease in nitrogen losses. The optimum levels of water, fertilizer and density based on environmental scenario were 1802 m³ ha^?1, 11 kg N ha^?1 and 122 plant m^?2, respectively. To achieve optimum conditions under the economic scenario, it is necessary to use 3411 m³ water ha^?1, 178 kg N ha^?1 and 119 plant m^?2. Amounts of 2347 m³ water ha^?1, 92 kg N ha^?1 and 114 plant m^?2 were found to be the optimum conditions for the eco-environmental scenario. In general, it seems that resource use based on the eco-environmental scenario may be the most favorable cropping strategy for canola production.     

How Nitrogen and Zinc Levels Affect Seed Yield,Quality, and Nutrient Uptake of Canola Irrigated with Saline and Ultra-Saline Water

In order to investigate the effects of nitrogen (N) and zinc (Zn) fertilizers on seed yield, oil percentage, glucosinolate content, and nutrient uptake of canola (Brassica napus L. cv. Okapi), irrigated with saline and ultra-saline water, field experiments were conducted in Agriculture Research Centre of East Azarbaijan, Iran, during three consecutive years: 2011, 2012, and 2013. The experiments were carried out based on randomized complete block design arranged in factorial with three replications. The experimental treatments included N rates at three levels (0, 50, and 100 kg ha^?1), Zn rates at three levels (0, 5, and 10 kg ha^?1), and saline water at two levels (8 and 16 dS m^?1 as saline and ultra-saline water). According to the results, N and Zn application had a significant effect on the plant height, pod number per plant, and seed yield. However, the value of these traits decreased as a result of the higher salinity level (from 8 to 16 dS m^?1). From the results, the glucosinolate content was not affected by N or Zn fertilization, whereas, salinity increased the glucosinolate content from 27.51% to 30.06% when saline water and ultra-saline water were applied, respectively. In addition, the effect of ultra-saline water on the decrease in the N, phosphorous, potassium, and calcium uptake and the increase in the sodium and chlorine accumulation in canola seed was significant. However, Zn application could diminish adverse effects of salinity on phosphorus uptake. For instance, under ultra-saline water conditions, application of 10 kg ha^?1 Zn increased the seed phosphorus content compared with control treatment. In general, it seems that nutrients’ supply, especially N and Zn, can be considered as an effective solution to diminish adverse effects of salinity.     

Long-Term Tillage,Straw Management,and Nitrogen Fertilization Effects on Organic Matter and Mineralizable Carbon and Nitrogen in a Black Chernozem Soil

Soil, crop, and fertilizer management practices may affect quality of organic carbon (C) and nitrogen (N) in soil. A long-term field experiment (growing barley, wheat, or canola)was conducted on a Black Chernozem (Albic Argicryoll) loam at Ellerslie, Alberta, Canada, to determine the influence of 19 years (1980 to 1998) of tillage [zero tillage (ZT) and conventional tillage (CT)], straw management [straw removed (S_Rem) and straw retained (S_Ret)], and N fertilizer rate (0, 50, and 100 kg N ha^?1 in S_Ret and 0 kg N ha^?1 in S_Rem plots) on macro-organic matter C (MOM-C) and N (MOM-N), microbial biomass C (MB-C), and mineralizable C (C_min) and N (N_min) in the 0- to 7.5-cm and 7.5- to 15-cm soil layers. Treatments with N fertilizer and S_Ret generally had a greater mass of MOM-C (by 201 kg C ha^?1 with 100 kg N ha^?1 rate and by 254 kg C ha^?1 with S_Ret), MOM-N (by 12.4 kg N ha^?1 with 100 kg N ha^?1 rate and by 8.0 kg N ha^?1 with S_Ret), C_min(by 146 kg C ha^?1 with 100 kg N ha^?1 rate and by 44 kg C ha^?1 with S_Ret), and N_min(by 7.9 kg N ha^?1 with 100 kg N ha^?1 rate and by 9.0 kg N ha^?1 with S_Ret)in soil than the corresponding zero-N and S_Rem treatments. Tillage, straw, and N fertilizer had no consistent effect on MB-C in soil. Correlations between these dynamic soil organic C or N fractions were strong and significant in most cases, except for MB-C, which had no significant correlation with MOM-C and MOM-N. Linear regressions between crop residue C input and mass of MOM-C, MOM-N, C_min, and N_min in soil were significant, but it was not significant for MB-C. The effects of management practices on dynamic soil organic C and N fractions were more pronounced in the 0- to 7.5-cm surface soil layer than in the 7.5- to 15-cm subsoil layer. In conclusion, the findings suggest that application of N fertilizer and retention of straw would improve soil quality by increasing macro-organic matter and N-supplying power of soil.     

Uptake and nutrient balance of nitrogen,sulfur, and boron for optimal canola production in eastern Canada

Balanced plant nutrition is essential to achieve high yields of canola (Brassica napus L.) and get the best economic return from applied fertilizers. A field study was conducted at nine site‐years across eastern Canada to investigate the effects of nitrogen (N), sulfur (S) and boron (B) fertilization on canola nutrient uptake, nutrient balance, and their relationship to canola yields. The factorial experiment consisted of four N rates of 0 (N0), 50 (N50), 100 (N100), and 150 (N150) kg ha^?1, two S rates of 0 (S0) and 20 (S20) kg ha^?1, and three B treatments of 0 (B0), 2 kg ha^?1 at preplant (B2.0P), and 0.5 kg B ha^?1 foliar‐applied at early flowering stage (B0.5F). Each site‐year used the same experimental design and assigned treatments in a randomized complete block design with four replications. Fertilizer S application greatly improved seed yields at six out of nine site‐years, and the highest N use efficiency was in the N150+S20 treatment. Sulfur application generally increased seed S concentration, seed S removal, and plant total S uptake, while B fertilization mainly elevated straw B concentration and content, with minimal effect on seed yields. At the early flowering stage, plant tissue S ranged from 2.2 to 6.6 mg S g^?1, but the N : S ratio was over or close to the critical value of 12 in the N150+S0 combination at five site‐years. On average across nine site‐years, canola reached a plateau yield of 3580 kg ha^?1 when plants contained 197 kg N ha^?1, 33 kg S ha^?1 and 200 g B ha^?1, with a seed B content of 60 g B ha^?1. The critical N, S, and B values identified in this work and their potential for a posteriori nutrient diagnosis of canola should be useful to validate fertilizer requirements for canola production in eastern Canada.     

Crop Utilization of Nitrogen in Swine Lagoon Sludge

Swine lagoon sludge is commonly applied to soil as a source of nitrogen (N) for crop production but the fate of applied N not recovered from the soil by the receiver crop has received little attention. The objectives of this study were to (1) assess the yield and N accumulation responses of corn (Zea mays L.) and wheat (Triticum aestivum) to different levels of N applied as swine lagoon sludge, (2) quantify recovery of residual N accumulation by the second and third crops after sludge application, and (3) evaluate the effect of different sludge N rates on nitrate (NO₃-N) concentrations in the soil. Sludge N trials were conducted with wheat on two swine farms and with corn on one swine farm in the coastal plain of North Carolina. Agronomic optimum N rates for wheat grown at two locations was 360 kg total sludge N ha^?1 and the optimum N rate for corn at one location was 327 kg total sludge N ha^?1. Residual N recovered by subsequent wheat and corn crops following the corn crop that received lagoon sludge was 3 and 12 kg N ha^?1, respectively, on a whole-plant basis and 2 and 10 kg N ha^?1, respectively, on a grain basis at the agronomic optimum N rate for corn (327 kg sludge N ha^?1). From the 327 kg ha^?1 of sludge N applied to corn, 249 kg N ha^?1 were not recovered after harvest of three crops for grain. Accumulation in recalcitrant soil organic N pools, ammonia (NH₃) volatilization during sludge application, return of N in stover/straw to the soil, and leaching of NO₃ from the root zone probably account for much of the nonutilized N. At the agronomic sludge N rate for corn (327 kg N ha^?1), downward movement of NO₃-N through the soil was similar to that for the 168 kg N ha^?1 urea ammonium nitrate (UAN) treatment. Thus, potential N pollution of groundwater by land application of lagoon sludge would not exceed that caused by UAN application.     

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.     

EFFECT OF NITROGEN AND SULFUR FERTILIZATION ON YIELD COMPONENTS,SEED AND OIL YIELDS OF CANOLA

Field experiments were conducted to evaluate the effects of nitrogen (N) and sulfur (S) levels and their methods of application on canola. Branches plant^?1, pods plant^?1 and biological yield significantly increased with increase in nitrogen level and no significant increase in seed pod^?1 and seed and oil yields occurred beyond 120 kg N ha^?1. However, thousand seed weight consistently decreased with increasing level of nitrogen. Pods plant^?1 and biological yield continually increased with increase in sulfur level. Alternatively, significant increase in branches plant^?1, seed pod^?1, seed weight, seed and oil yields was noted with increase in sulfur level up to 40 kg ha^?1. Applications of sulfur and nitrogen in split significantly decreased seed yield as compared to sole applications. It is concluded that sulfur and nitrogen application as sole at the rate of 40 and 120 kg ha^?1, respectively performed better than the rest of their levels and method of application.     

Wheat Nitrogen Fertilization Under no Till on the Low Altitude Brazilian Cerrado

This study evaluates the effects of different nitrogen (N) rates (0, 50, 100, 150, and 200 kg ha^?1) and sources (ammonium sulfate, urea, and ammonium sulfonitrate with a nitrification inhibitor, Entec®) applied either as a single application during sowing (next to the planting rows) or as side dressing (stage 3.2 on Zadok scale), on production components and grain yield of irrigated wheat grown under no-till in a low-elevation Brazilian cerrado and Dark Red Dystrophic Latosol with clayey-texture. It was adopted a randomized block design (5 × 3 × 2) in factorial scheme with four replications. The N sources provided similar grain yields and chlorophyll contents. Increased nitrogen rates increased grain yield up to the 120 kg N ha^?1, regardless of application time and N source. Nitrogen fertilization as side dressing can be recommended based on leaf chlorophyll readings. Early application of all nitrogen fertilizers at sowing time was viable.