Effect of nitrogen and water uptake on yield of wheat

For 2 years, field experiments were conducted to study the direct and interactive effects of water and nitrogen uptake at different growth stages on grain yield of wheat, grown on coarse textured alluvial soil of Ludhiana. Twelve treatments comprising 3 irrigation regimes and 4 rates of N were imposed. The N and irrigation regimes showed significant interaction, especially during the drier year. Grain yield was better explained with water uptake and N uptake, when partitioned over different growth stages than with total uptake. The sensitivity factor for water uptake was higher at the reproductive stage ( = 1.60) than at the vegetative ( = 1.05) and maturation ( = 0.38) stages. Contrary, yield was more sensitive to N uptake during the vegetative stage than the reproductive and the maturation stages. Sensitivity of grain yield to water uptake was higher at higher N application rates. Yield predictability was much better (R² = 0.98) when N and water uptake at different growth stages were combined.     

Response surface analysis of the effects of seeding rates,N-rates and irrigation frequencies on durum wheat I. Grain yield and yield components

Interactive effects of nitrogen (N) rates, seeding (S) rates and irrigation frequencies on grain yield and yield components of durum wheat were studied for four years under field conditions at Tulelake, California. Each year the experiment was conducted using a split-plot design with 4 irrigation frequencies as main plots and combinations of 5 N-rates (0 to 360 kg/ha) and 5 S-rates (50 to 250 kg/ha) as subplot treatments replicated 4 times. A quadratic response surface model (RSM) was used to study the effects of these treatments on grain yield and yield components (tillers/area, kernel number/spike, kernel weight/spike and 100-seed weight). The RSM was very effective for analysis and data reduction for estimating the optimum combinations of N and S for maximizing the grain yield and yield components. The N utilization and uptake efficiency increased with each irrigation treatment and peaked at irrigation treatment C. Both N and uptake utilization efficiency decreased with each increment of N-rate.In most cases, the effect of irrigation was independent of N and S. One irrigation at tillering increased grain yield and yield components significantly over only a preplant irrigation. The response of additional irrigations were comparatively small and significant only in some cases. Both N and S had significant effects on grain yield and yield components, however, the response of N was larger than that of S. With increasing N-rate, grain yield and tiller number increased with the expected peak beyond 360kg N ha^–1 but the increments beyond 180 kg N ha^–1 were of progressively smaller magnitude. The kernel number and kernel weight per spike also increased with N-rate giving a peak between 270 and 360 kg N ha^–1. With increasing S grain yield and tiller number/area increased while kernel number and kernel weight per spike decreased progressively. It was impossible to maximize yield and yield components at a given combination of N, S, and irrigation. According to the model, grain yield and tiller number were maximized at the highest level of N and S, while kernel number and kernel weight/spike were maximized at the lowest S (50 kg ha^–1) and about 314 kg N ha^–1 under adequate water supply. On the basis of the findings of this study and output of the model, 180–360 kg N ha^–1, 150–250 kg S ha^–1 and two post-sowing irrigations (at tillering and at boot stage) in addition to a preplant irrigation was recommended for optimum yield. An additional irrigation might be required depending on the weather conditions during the grain filling period.     

Yield,water use and nitrogen uptake for different water and N levels in winter wheat

In an effort to establish an optimum combination of water and nitrogen for winter wheat a field investigation was carried out on a coarse loamy sand soil during 1984–85 and 1985–86 to assess effects of irrigation regime (IR) and N application on yield, water use and N uptake. The treatments compromised all combinations of three irrigation regimes (IR) based on ratios of irrigation water to cumulative pan evaporation viz.1.2 (I-1), 0.9 (I-2) and 0.6 (I-3) and four rates of N, viz. 0, 60, 120 and 180 kg ha^–1. Grain yield increased with increase in frequency of irrigation. In spite of wide differences in weather during the two years, scheduling of irrigation at IW/CPE = 1.2 gave the highest wheat yield on the coarse-textured soil. During 1984–85, the rainless year, grain yield under I-1 was 20 and 32 per cent higher than I-2 and I-3, respectively. With increasing N rate the yield and water use efficiency increased progressively upto 180 kg N under I-1 and upto 120 kg N ha^–1 under I-2 and I-3 regimes. During 1985–86, the wet year, grain yield response to IR was relatively low. Irrespective of IR, yield increased progressively upto 180 kg N ha^–1 during the wet year. Irrigation water regimes and N application also influenced leaf area index and root growth of wheat. The yield of unfertilized wheat was relatively less affected by seasonal rainfall and IR.Both N uptake and grain yield of wheat were found to increase linearly with increase in water use. Water use efficiency was highest under I-1 regime at all levels of N in the dry season of 1984–85 and under I-3 regime in the wet season of 1985–86. Increase in N uptake with increasing N rates was significantly higher under I-1 than I-2 and I-3 regimes. The N use efficiency being maximum at 60 kg N ha^–1, decreased at higher N levels irrespective of IR.     

Yield,water use,and nutrient uptake of corn hybrids under varied irrigation and nitrogen regimes

Defined relationships among grain yields, water-use efficiencies (WUE) and nutrient uptake of different genotypes under varied irrigation and nitrogen (N) regimes would be invaluable for optimizing production of corn (Zea mays L.). Our objective was to evaluate these factors for six popular corn hybrids grown in Nebraska. The procedure involved measuring the effects of three supplemental irrigation rates and two N rates on yields, consumptive water use (ET), water-use efficiency, and nutrient uptake of these hybrids in one field experiment. A second field experiment evaluated effects of irrigation timing on the same characteristics of the six hybrids. Soils employed for the field experiments were Sharpsburg sicl, a typic Argiudoll, and Zook sicl, a cumulic Haplaquoll. In addition, two greenhouse experiments measured above-ground and root yields, water use, and nutrient uptake of the six hybrids under limited and high soil moisture levels.From 30–40 percent reductions in grain and stover yields occurred by limiting moisture supply in the greenhouse but with no reduction in root yields. There was only a small benefit to grain and stover yields from the higher soil moisture levels provided in the field experiments because of very favorable rainfall amount and distribution in 1979. Light, frequent irrigation was advantageous to yield and WUE over the same total amount of water applied in larger, less frequent intervals explainable in part by a N use efficiency factor. Genotype B73xMo17 produced significantly higher grain, stover, root and total yields than the other hybrids under all moisture and N regimes. Amounts of water consumed by the six hybrids in the field experiments were similar, but because of higher yields B73xMo17 had the highest WUE values. This hybrid had greater root development in the field and took up disproportionately more P, Ca, S, Fe, Cu, and Zn and less Mn and Cl than the other hybrids suggesting that its superior yielding capacity may be related to efficiency in mobilizing and utilizing certain nutrients.Contribution of the Nebraska Agric Exp Stn, Lincoln, NE as paper No. 7041 Journal Series.     

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.     

Irrigation and nitrogen managements affect nitrogen leaching and root yield of sugar beet

Irrigation water and nitrogen (N) are the limiting factors for crop production in arid and semi-arid areas. However, excess irrigation and N application rate is a source of groundwater contamination. Partial root drying irrigation (PRD) is the water-saving technique and would perform as a controlling measure of groundwater N contamination as it reduces irrigation amount. Sugar beet is an industrial crop that is widely grown in arid and semi-arid area where N and water are highly required for high sugar beet yield production. The objectives of this study were to evaluate the interaction effect of ordinary furrow irrigation (OFI), and PRD irrigation as variable alternate furrow irrigation (VAFI) and fixed alternate furrow irrigation (FAFI) with different N application rates (0, 80, 160, and 240 kg ha^?1) on sugar beet root and sugar yield, yield quality, drainage water, N leaching, N uptake, and N efficiency indices. Results indicated that the alternate furrow irrigation (AFI) used 24% less irrigation water compared with the OFI in the study region, whereas its sugar yield was reduced just by 9%. However, it resulted in higher water productivity by 12 and 17% for root and sugar yields, respectively. In different N application rates nitrate leaching reduced by 46 and 52% in the VAFI and FAFI irrigation treatments compared with the OFI, respectively. Physiologic nitrogen efficiency enhanced in VAFI with 160 kg N ha^?1 that implied higher production of uptake N in plants. Therefore, considering the nitrogen use economics and environmental impacts, the VAFI and 160 kg N ha^?1 were preferred to the other irrigation treatments and N application rates in the study region. Higher nitrogen saving occurred because of less leaching and higher soil residual in the AFI treatment compared with the OFI. Furthermore, leaf level stress sensitivity index indicated that VAFI increased the sugar beet resistance to water stress. Overall, in order to avoid N losses in sugar beet production, the amount of N fertilizer should be reduced in proportion to the amount of soil water available under VAFI water-saving irrigation.     

Leaching losses of urea-N applied to permeable soils under lowland rice

Application of 120 kg urea-N ha^–1 to lowland rice grown in a highly percolating soil in 10 equal split doses at weekly intervals rather than in 3 equal split doses at 7, 21 and 42 days after transplanting did not significantly increase rice grain yield and N uptake. Results suggest that leaching losses of N were not substantial. In lysimeters planted with rice, leaching losses of N as urea, NH ₄ ⁺ , and NO ₃ ^- beyond 30 cm depth of a sandy loam soil for 60 days were about 6% of the total urea-N and 3% of the total ammonium sulphate-N applied in three equal split doses. Application of urea even in a single dose at transplanting did not result in more N leaching losses (13%) compared to those observed from potassium nitrate (38%) applied in three split doses. Nitrogen contained in potassium nitrate was readily leached during the first week of its application. More N was lost from the first dose of N applied at transplanting than from the second or third dose. Data pertaining to yield, N uptake and per cent N recovery by rice revealed that the performance of different fertilizer treatments was inversely related to susceptibility of N to leaching.     

Plastic-film mulch and fertilization rate affect the fate of urea-<Superscript>15</Superscript>N in maize production

We investigated the effects of interaction between plastic-film mulch and nitrogen (N) fertilization rate on the fate of fertilizer N in a ridge–furrow maize (Zea mays L.) cropping system. Three N levels (0, 138 and 207 kg ha^?1, abbreviated as N0, N1 and N2) were combined with plastic-film-mulching and no-mulching, successively in 2015 and 2016, at a cold semiarid site. Within each treated plot, a micro-plot was established to trace the fate of urea-N (only ¹⁵N-labeled in 2015). Averaging 2 years, increasing fertilization from N1 to N2 increased maize grain yield and total N uptake only in mulched soils. Mulch increased both maize grain yield and total N uptake more at N2 than at N1. In 2015, mulch increased the in-season fertilizer N uptake in maize by 53% at N1 but by 75% at N2; increasing N application from N1 to N2 enhanced the fertilizer N acquisition by 26% in non-mulched but by 45% in mulched plots. In 2016, similar effects of interaction existed between mulch and fertilization rate on the residual fertilizer N uptake by maize. Mulch enhanced fertilizer N availability in the topsoil relative to no mulch, responsible for the increased maize fertilizer N uptake in mulched treatments. Decreased in-season fertilizer N loss and transformation of urea N to the organic N in mulched soils were contributors to the increased fertilizer N availability, compared to non-mulched soils. We concluded that the effects of fertilization on maize total N uptake and fertilizer N recovery benefited from plastic-film mulch.     

Response of tomato to nitrogen fertilization and irrigation frequencies in a semi-arid tropical soil

The effect of different irrigation frequencies (5, 7 and 9 days interval) and N rates (0, 50, 100 and 150 kg N ha^–1) on applied N in tomato was studied in a field experiment during 3 growing seasons. The application of 100 kg N ha^–1 with irriga tion scheduled at 7 days interal resulted in significantly higher N uptake and recovery rate than the other combinations of N rate and irrigation frequencies studied.     

Nitrogen use efficiency of irrigated tropical rice established by broadcast wet-seeding and transplanting

Broadcast wet-seeding is gradually replacing transplanting in irrigated rice systems of Southeast Asia. Previous studies reported higher fertilizer-N use efficiency for broadcast-seeded than transplanted rice despite similar grain yields in treatments that received N fertilizer. To re-examine this issue, we compared crop performance and the recovery efficiency (_r, N uptake per unit N applied), agronomic efficiency (_a, grain yield per unit N applied), and partial factor productivity from applied N (PFP, grain yield per unit N applied) in broadcast-seeded and transplanted rice across a wide range of N fertilizer rates at research stations and in farmers' fields. Rice crop established by broadcasting had more rapid leaf area development, dry matter accumulation, and N uptake than transplanting during vegetative growth stages, but slower growth rates and N uptake after panicle initiation, particularly during the grain filling period. Without applied N, grain yield and N accumulation at maturity were significantly lower in broadcast-seeded than transplanted rice, whereas yields and N uptake were comparable for both planting methods with equivalent rates of applied N. Although both _r and _a were higher for broadcast-seeded than transplanted rice, this advantage was an artifact of lower yields and reduced N uptake by broadcasting without applied N rather than improved performance with applied N. In contrast, PFP values were similar for broadcast-seeded and transplanted rice at comparable fertilizer-N rates and in the absence of lodging. We conclude that the PFP from applied N provides a more relevant measure of N use efficiency of different crop establishment methods, and that the system-level N use efficiency of broadcast-seeded rice was not greater than that of transplanted rice.     

The effect of fertilizer placement on nitrogen uptake and yield of wheat and maize in Chinese loess soils

Field trials were carried out to study the fate of¹⁵N-labelled urea applied to summer maize and winter wheat in loess soils in Shaanxi Province, north-west China. In the maize experiment, nitrogen was applied at rates of 0 or 210 kg N ha^–1, either as a surface application, mixed uniformly with the top 0.15 m of soil, or placed in holes 0.1 m deep adjacent to each plant and then covered with soil. In the wheat experiment, nitrogen was applied at rates of 0, 75 or 150 kg N ha^–1, either to the surface, or incorporated by mixing with the top 0.15 m, or placed in a band at 0.15 m depth. Measurements were made of crop N uptake, residual fertilizer N and soil mineral N. The total above-ground dry matter yield of maize varied between 7.6 and 11.9 t ha^–1. The crop recovery of fertilizer N following point placement was 25% of that applied, which was higher than that from the surface application (18%) or incorporation by mixing (18%). The total grain yield of wheat varied between 4.3 and 4.7 t ha^–1. In the surface applications, the recovery of fertilizer-derived nitrogen (25%) was considerably lower than that from the mixing treatments and banded placements (33 and 36%). The fertilizer N application rate had a significant effect on grain and total dry matter yield, as well as on total N uptake and grain N contents. The main mechanism for loss of N appeared to be by ammonia volatilization, rather than leaching. High mineral N concentrations remained in the soil at harvest, following both crops, demonstrating a potential for significant reductions in N application rates without associated loss in yield.     

Using mucuna and P fertilizer to increase maize grain yield and N fertilizer use efficiency in the coastal savanna of Togo

To reduce severe soil degradation associated with agriculture an intensified land-use system is being promoted in West African countries. Most soils of the West African savanna zones are so poor that the efficiency of mineral fertilizers, if applied, is very low. For this reason and because of their high cost and unavailability, many small-scale farmers are reluctant to apply fertilizer. This work investigates a fertilizer management strategy using integrated soil fertility management with a leguminous cover crop (mucuna) so as to improve the soil fertility and increase the use efficiency of fertilizer. The experiment was conducted in the coastal savanna of Togo at Djaka Kopé. The aim was to evaluate the effectiveness of mucuna short fallow (MSF) in increasing maize grain yield through an improved use efficiency of mineral fertilizer. A 2-year maize–mucuna relay intercropping system was compared with continuous sole maize cropping. Fertilizer treatments were factorial combinations of 0, 50 and 100 kg nitrogen (N) ha^–1 and 0, 20 and 40 kg phosphorus (P) ha^–1. While maize grain yield was significantly increased by N fertilization, P did not show any important effect on grain yield. With no N and P applied, grain yield after MSF was on average 40% (572 kg ha^–1) higher than without. The response to N was much greater than the response to MSF, indicating that N was undoubtedly the key element for maize yield building. P fertilization and MSF together positively influenced the apparent N recovery fraction (NRF). N uptake alone did not reflect on its own the yield obtained, and the relationship between grain yield and N uptake is shifted by MSF, with the grain yield increase per unit of N uptake being higher with than without MSF. Combining MSF and P fertilization may therefore lead to improved N use efficiency, making the application of fertilizer N (lower rates) more attractive to small-scale farmers.     

Response of dryland wheat to small supplemental irrigation and fertilizer nitrogen in submontane Punjab

In northern India, the monsoon rains recede much earlier than the sowing time of post-rainy crops and the seed-zone gets dried. Excess rain water collected in near-farm or on-farm reservoirs permits small presowing and/or postsowing irrigation(s) to increase yield which is also limited by N supplies. Field experiments were conducted to match N application rates with available water supplies to optimise wheat (Triticum aestivum L.) yields. Five rates of fertilizer N (0, 25, 50, 75 and 100 kg ha^–1) were combined with five irrigation treatments (no-irrigation; 5 cm and 10 cm presowing irrigation, 5 cm irrigation 30 days after sowing and; equal presowing and postsowing irrigations totalling 10 cm). The yield was regressed over crop water supply inclusive of irrigation (W) or exclusive of irrigation (W₁) and applied nitrogen (N). Grain yield increased with increase in both water supply and N-rate. Within certain limits N and W₁ substituted each other for yield and so did irrigation and W₁. Irrespective of irrigation, the amount of N required to substitute for given W₁ to maintain a given yield decreased with increasing W₁. At low W₁, irrigation substituted for small changes in W₁ but with increased W₁, irrigation substituted for larger changes in W₁. Also with increase in N level given irrigation substituted for smaller amount of W₁. These regressions permit recommendations of N in relation to stored water and seasonal rain with or without limited irrigation. The latter was most useful at intermediate W₁.     

Response of irrigated maize to urea-ammonium nitrate and ammonium thiosulphate solutions on a sulphur deficient soil

Ammonium thiosulphate solution, (ATS, (NH₄)₂S₂O₃, 12% NH₄-N and 26% S), is a nitrogen-sulphur fertiliser which can also inhibit nitrification, inhibit area hydrolysis and also solubilize micronutrients in alkaline soils. A three year field study was conducted in northeastern Italy to compare the growth, yield, and nutrient uptake of irrigated maize (Zea mays L.) fertilised with 250 kg N ha^-1 urea-ammonium nitrate solution (UAN, 30-0-0) or UAN plus ATS. Dry matter (DM) yield, sulphur (S) and nitrogen (N) uptake were measured at several growth stages. Grain was measured and analyzed at maturity. Maize grain yield and N uptake were increased respectively 30.6% and 42.2% in the first year by adding ATS to UAN. Adding 10% by weight ATS to UAN (22.8 kg S ha^-1) increased grain yields by 1.9, 1.7 and 1.6t ha^-1 for the three years of the study. To distinguish whether the response was due to S or other ATS attributes, ATS was compared to an equivalent amount of S from single superphosphate (SSP). Plots fertilised with ATS gave grain yields 0.5 and 1.2 t ha^-1 greater than plots fertilised with equal rates of S from SSP in the last two years of the study. This added yield from ATS over SSP may have been due to beneficial effects of ATS on N or micronutrient availability or to the split application of the S from ATS.     

Effect of phenyl phosphorodiamidate on the fate of urea applied to wetland rice fields

The effect of phenyl phosphorodiamidate (PPD) on floodwater properties, N uptake,¹⁵N recovery, and grain yield of wetland rice (Oryza sativa L.) was evaluated in a series of field studies conducted at Muñoz and Los Baños, Philippines. Prilled urea and PPD-amended urea were applied to soil and incorporated immediately prior to transplanting or applied to floodwater after transplanting. Urea was also deep-placed or added in a coated form in two studies.The addition of PPD with urea retarded urea hydrolysis by 1–3 days, depending on the time and method of application. Significant reductions in the concentration of ammoniacal-N in floodwater resulted when PPD-amended urea was applied between 18 and 26 days after transplanting (DT). In contrast, PPD did not appreciably affect the concentration of ammoniacal-N in floodwater when applied with urea either immediately before or after transplanting of the seedlings.Plant N uptake and grain yield were not significantly affected by the addition of PPD with urea in three of the four experiments conducted, even though PPD substantially reduced the concentration of ammoniacal-N in the floodwater in several treatments in these studies. The¹⁵N balance studies conducted at both field locations showed PPD to increase total¹⁵N recovery by between 10% and 14% of the¹⁵N applied, 14 days after the application of urea. No further loss of¹⁵N occurred between the initial sampling (40 DT) and grain harvest at Los Baños. An increase in¹⁵N recovery occurred at grain harvest at Muñoz because¹⁵N-labeled urea was applied at 50 DT in the study. PPD increased the amount of¹⁵N in the plant and nonexchangeable soil N fraction at all harvests at Los Baños. In contrast, at Muñoz, PPD increased the quantity of¹⁵N in the KCL-extractable pool 14 days after urea was applied. Reasons for the discrepancies in results between experiments and the overall failure of PPD to increase grain yield are discussed.     

Comparison of efficiency of Mussoorie partially acidulated phosphate rock and single superphosphate in a shallow Alfisol of the Indian semiarid tropics

The agronomic effectiveness of a partially acidulated phosphate rock (PAPR) was measured in a field experiment with sorghum (Sorghum bicolor cv. CSH-6) in a shallow Alfisol at the ICRISAT farm, Patancheru (Hyderabad), India. The experiment compared PAPR with single superphosphate. The PAPR was made by acidulating an indigenous Indian phosphate rock (Mussoorie) with H₂SO₄ at 50% acidulation level. P response was evaluated at a single relatively high N rate (120 kg ha^–1) with five rates of P (0, 2.2, 4.4, 8.8, and 17.6 kg P ha^–1). A significant response to P was obtained at rates up to 17.6kg P ha^–1.There was no significant difference due to source of P in terms of sorghum grain yield or total P uptake. Both Olsen and Bray 1 soil tests underestimated P availability from PAPR with respect to that from SSP.A rapid rate of P uptake was observed during grain filling to maturity (81–102 days), when 40% of the total P was taken by the plant. The internal efficiency of both P sources was the same.     

Potential for nitrogen mineralization in central Alberta soils

Incubation experiments were conducted to determine the relationship between N mineralization potential of soils and yield or N uptake of barley grain. In addition, the effect of soil type and soil depth on N mineralization potential was investigated. In an experiment with 39 cultivated surface soil samples varying in organic C from 1.5 to 8.6%, the amount of mineralized N (as determined by the incubation method of Stanford and Smith, 1972) ranged from 34 to 111 mg N kg^?1 over a 12-week period but the correlation coefficient between mineralized N and soil organic C was only 0.49^**. Mineralized N was not correlated with grain yield or N uptake (r = 0.29 or 0.32, respectively), but there was a fairly close correlation between soil NO₃-N at sowing and yield (r = 0.79^**) or N uptake of barley grain (r = 0.82^**). Combining soil NO₃-N at sowing and mineralized N on incubation did not improve correlation. In the other experiment with just two soils, the mineralized N sharply decreased with increasing soil depth.     

Growth and acetylene reduction activity ofAzolla caroliniana Willd. as influenced by split applications of urea fertilizer and their response on rice yield

Experiment with different split applications of 40 kg N ha^–1 of urea (U) at transplanting:30 days after transplanting:40 days before crop maturity with different proportions of 50:25:25, 25:50:25 and 0:50:50 splits, with and without Azolla, carried out for two consecutive seasons, revealed that fresh weight (FW), N₂-fixation measured by acetylene reduction activity (ARA) and N yield of newly introducedAzolla caroliniana were higher with 0:50:50 treatment followed by 25:50:25 and 50:25:25.Azolla was unincorporated and left for self decomposition. The crop yield (grain yield, straw yield) and crop N uptake data indicated that among the no Azolla treatments, the use of 50:25:25 split resulted in highest crop yield and crop N uptake followed by 25:50:25 and 0:50:50 treatments, while these parameters recorded maximum value with 25:50:25 split in combination with Azolla followed by 50:25:25 and 0:50:50 treatments. The use of Azolla increased crop yield and crop N uptake significantly over no Azolla treatments.     

Spent mushroom compost as a nitrogen source for spring barley

Spent mushroom compost (SMC) contains a range of plant nutrients, including nitrogen (N), a large proportion of which originate from arable crops. Using SMC as an organic fertilizer for crops recycles these nutrients. Effective use of SMC in fertilizer regimes requires knowledge of the nitrogen fertilizer value (NFV) of the SMC, which is the amount of mineral fertilizer N required to give the same N yield, or marketable yield, as an application of SMC. The objectives of these experiments were to evaluate the effect of SMC on spring barley grain yield and quality and to determine its NFV. Experiments were carried out on two soils, light- and medium-textured, over 3 years (2008–2010). The experiments compared the yield response and N uptake of spring barley to fertilizer N with and without SMC. SMC application gave similar or higher grain yield and N uptake compared to fertilizer only treatments at corresponding fertilizer N rates. SMC had no significant (P > 0.05) effect on the economic optimum fertilizer N rate but the maximum yield was significantly (P < 0.05) higher where SMC was applied in two of the six experiments. Effects of SMC on grain quality were small. Results indicated that the NFV, expressed as a proportion of the total N applied in SMC, ranged from 0.05 to 0.29 kg kg^?1 N applied in SMC, with a mean of 0.15 kg kg^?1. It is concluded that SMC can contribute to the nitrogen nutrition of small grain cereal crops in high yield potential environments.     

Estimating the crop response to fertilizer nitrogen residues in long-continued field experiments

Knowledge of the cumulated effect of long-continued nitrogen (N) inputs is important for both agronomic and environmental reasons. However, only little attention has been paid to estimate the crop response to mineral fertilizer N residues. Before interpreting estimates for the crop response to previous N input rates, the experimental design for testing needs to be examined. Experimental designs that suspend the customary N inputs, leaving the test crop unfertilized, ignore any interaction between the rate of N applied in the past and the rate applied in the test year. We estimated the interaction using data from five long-continued field experiments on mineral and organic N input rates where the main plots were subdivided for incremental rates of mineral N fertilizer in the test year. The interaction between N applied in the past and in the test year significantly affected grain yield and N offtake when the residual effect originated from organic applications, but the interaction was not significant when mineral N fertilizer had been used in the past, making the residual effect of N applied in the past additive to the effect of N applied in the test year. The dry matter (DM) grain yield of spring barley decreased by an average of 5?kg?DM/ha and the grain N offtake by 46?g?N/ha for a decrease in the annual mineral N rate of 1?kg?N/ha applied for more than three decades. Although statistically significant, the crop response to mineral fertilizer N residues was of minor importance when compared with the residual effect of organic inputs.