Nitrogen losses and fertilizer N use efficiency in irrigated porous soils

Porous soils are characterized by high infiltration, low moisture retention and poor fertility due to limitation of organic matter and nitrogen (N). However, wherever irrigated and properly managed, these are among the most productive soils in the world. For sustained productivity and prevention of N related pollution problems, fertilizer N management in porous soils needs to be improved by reducing losses of N via different mechanisms. Losses of N through ammonia volatilization are not favoured in porous soils provided fertilizer N is applied before an irrigation or rainfall event. Ammonium N transported to depth along with percolating water cannot move back to soil surface where it is prone to be lost as NH₃. Under upland conditions nitrification proceeds rapidly in porous soils. Due to high water percolation rates in porous soils, continuous flooding for rice production usually cannot be maintained and alternate flood and drained conditions are created. Nitrification proceeds rapidly during drained conditions and nitrates thus produced are subsequently reduced to N₂ and N₂O through denitrification upon reflooding. Indirect N-budget estimates show that up to 50% of the applied N may be lost via nitrification-denitrification in irrigated porous soils under wetland rice.High soil nitrate N levels and sufficient downward movement of rain water to move nitrate N below the rooting depth are often encountered in soils of humid and subhumid zones, to a lesser extent in soils of semiarid zone and quite infrequently, if at all in arid zone soils. The few investigations carried out with irrigated porous soils do not show substantial leaching losses of N beyond potential rooting zone even under wetland rice. However, inefficient management of irrigation water and fertilizer N particularly with shallow rooted crops may lead to pollution of groundwater due to nitrate leaching. At a number of locations, groundwater beneath irrigated porous soils is showing increased nitrate N concentrations. Efficient management of N for any cropping system in irrigated porous soils can be achieved by plugging losses of N via different mechanisms leading to both high crop production and minimal pollution of the environment.     

Use of nitrification inhibitors to increase fertilizer nitrogen recovery and lint yield in irrigated cotton

This paper describes field experiments designed to evaluate the effectiveness of several nitrification inhibitors to prevent loss of fertilizer nitrogen (N) applied to cotton. The usefulness of nitrapyrin, acetylene (provided by wax-coated calcium carbide), phenylacetylene and 2-ethynylpyridine to prevent denitrification was evaluated by determining the recovery of N applied as¹⁵N labelled urea to a heavy clay soil in 1 m × 0.5 m microplots in north western N.S.W., Australia. In a second experiment, the effect of wax-coated calcium carbide on lint yield of cotton supplied with five N levels was determined on 12.5 m × 8 m plots at the same site.The¹⁵N balance study showed that in the absence of nitrification inhibitors only 57% of the applied N was recovered in the plants and soil at crop maturity. The recovery was increased (p < 0.05) to 70% by addition of phenylacetylene, to 74% by nitrapyrin, to 78% by coated calcium carbide and to 92% by 2-ethynylpyridine.In the larger scale field experiment, addition of the wax-coated calcium carbide significantly slowed the rate of NH ₄ ⁺ oxidation in the grey clay for approximately 8 weeks. Lint yield was increased (p < 0.05) by the addition of the inhibitor at all except the highest level of N addition. The inhibitor helped to conserve the indigenous N as well as the applied N.The research shows that the effectiveness of urea fertilizer for cotton grown on the heavy clay soils of N.S.W. can be markedly improved by using acetylenic compounds as nitrification inhibitors.     

Effect of irrigation scheduling on grain yield and nitrogen use efficiency of irrigated wheat at Kadawa and Bakura,northern Nigeria

In this study the interaction of applied N with different irrigation schedules on grain yields and N use efficiency of wheat was investigated in two Inceptisols of the Nigerian savanna during 1978–80. Irrigation intervals ranged from 7 to 28 days at Kadawa and 5 to 10 days at Bakura while the N rates varied from 0 to 200 kg per ha. Both grain yield and N uptake increased significantly with increasing N rates at both the locations. The magnitude of increase in yield and N uptake decreased substantially when the irrigation interval became longer. This interaction was very pronounced at Bakura where the soil is highly porous, excessively drained and extremely poor in moisture retention capacity. Longer irrigation intervals produced grains with slightly higher N content but the difference was not significant. Higher N rates and fewer irrigations gave lower fertilizer N recovery.     

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.     

Seeding,nitrogen and irrigation management optimize rice water and nitrogen use efficiency

Nutrient Cycling in Agroecosystems - Adoption of appropriate agronomic practices, such as optimum seeding and nitrogen (N) rates, in synchronization with proper water management practice could help...     

Nitrogen-15 balances and nitrogen fertilizer use efficiency in upland rice

Field experiments were conducted in the 1984 and 1985 wet seasons to determine the effect of N fertilizer application method on¹⁵N balances and yield for upland rice (Oryza sativa L.) on an Udic Arguistoll in the Philippines. The test cultivars were IR43 and UPLRi-5 in 1984 and IR43 in 1985. Unrecovered¹⁵N in¹⁵N balances for 70 kg applied urea-N ha^–1, which represented N fertilizer losses as gases and movement below 0.5 m soil depth, ranged from 11–58% of the applied N. It was lowest (11–13%) for urea split applied at 30 days after seeding (DS) and at panicle initiation (PI), and highest (27–58%) for treatments receiving basal urea in the seed furrows. In all treatments with basal-applied urea, most N losses occurred before 50 DS.Heavy rainfall in 1985 before rice emergence resulted in large losses of native soil N and fertilizer N by leaching and possibly by denitrification. During the week of seeding, when rainfall was 492 mm, 91 kg nitrate-N ha^–1 disappeared from the 0.3-m soil layer in unfertilized plots. Although rainfall following the basal N application was less in 1984 than in 1985, the losses from basal applied urea-N were comparable in the two years. Daily rainfall of 20–25 mm on 3 of the 6 days following basal N application in 1984 may have created a moist soil environment favorable for ammonia volatilization.In both years, highest grain yield was obtained for urea split-applied at 30 DS and at PI. Delayed rather than basal application of N reduced losses of fertilizer N and minimized uptake of fertilizer N by weeds.     

The efficiency of fertilizer nitrogen in irrigated,direct seeded rice (O. sativa L.) in Europe

Data from 35 experiments with direct seeded rice, performed between 1981 and 1991 by national research institutes in five major rice growing countries of Europe were analyzed to estimate the average efficiency of fertilizer nitrogen (N). Pooled data from a four year regional survey (1984–1988) on rice-based farming systems in the Camargueregion (43° 20'–43° 40' N) in the south of France, were used to perform a similar analysis. Experimentation during two years (1989–1990) was carried out to assess the value of the N-utilization efficiency within the range of N-limited growth and to obtain information on the N-efficiency under controlled conditions.At reduced basal dressing of N on soils with high soil organic matter content, the apparent N-recovery was estimated at 0.21 to 0.32 kg N uptake per kg N applied. Average agronomic efficiency ranged from 12 to 17 kg grain dry mass per kg N applied. High basal N-application on these soils resulted in yield loss. No consistent yield response to fertilizer-N input was found on soils with less than two percent organic matter, irrespective of fertilizer timing. These results confirm the important role of soil organic matter in rice cultivation.An average apparent N-recovery of 0.18 was obtained with split application of N under controlled experimental conditions in the Camargue. Using a controlled release fertilizer, values of 0.58 and 32 kg.kg^–1 were obtained for the apparent N-recovery and agronomic efficiency, respectively. Hence, disregarding the economic feasibility, considerable scope exists for improving N-efficiency in European rice cultivation.     

Reducing nitrous oxide emissions and optimizing nitrogen-use efficiency in dryland crop rotations with different nitrogen rates

Recent interests in improving agricultural production while minimizing environmental footprints emphasized the need for research on management strategies that reduce nitrous oxide (N₂O) emissions and increase nitrogen-use efficiency (NUE) of cropping systems. This study aimed to evaluate N₂O emissions, annualized crop grain yield, emission factor, and yield-scaled- and NUE-scaled N₂O emissions under continuous spring wheat (Triticum aestivum L.) (CW) and spring wheat–pea (Pisum sativum L.) (WP) rotations with four N fertilization rates (0, 50, 100, and 150 kg N ha^?1). The N₂O fluxes peaked immediately after N fertilization, intense precipitation, and snowmelt, which accounted for 75–85% of the total annual flux. Cumulative N₂O flux usually increased with increased N fertilization rate in all crop rotations and years. Annualized crop yield and NUE were greater in WP than CW for 0 kg N ha^?1 in all years, but the trend reversed with 100 kg N ha^?1 in 2013 and 2015. Crop yield maximized at 100 kg N ha^?1, but NUE declined linearly with increased N fertilization rate in all crop rotations and years. As N fertilization rate increased, N fertilizer-scaled N₂O flux decreased, but NUE-scaled N₂O flux increased non-linearly in all years, regardless of crop rotations. The yield-scaled N₂O flux decreased from 0 to 50 kg N ha^?1 and then increased with increased N fertilization rate. Because of non-significant difference of N₂O fluxes between 50 and 100 kg N ha^?1, but increased crop yield, N₂O emissions can be minimized while dryland crop yields and NUE can be optimized with 100 kg N ha^?1, regardless of crop rotations.

     

Efficiency of nitrogen fertilizer use under rainfed maize and irrigated wheat at Kadawa,northern Nigeria

Field trials were conducted at Kadawa, northern Nigeria, during 1975–77 to study the efficiency of nitrogen fertilizer use under maize (Zea mays L.)—wheat (Triticum aestivum L.) rotation; the study also examined the impact of continuous N use on some soil properties. Grain and straw dry matter yields, grain N content, crop N uptake and whole plant N concentration of wheat at different growth stages increased significantly with increasing levels of N application. Per cent increases in mean grain yield of N treated plots over control were 77, 131 and 141 for maize and 195, 308 and 326 for wheat at 60, 120 and 180 kg N per ha levels, respectively. The calculated N rates for maximum yield were 177.5 and 164.0 kg N per ha for maize and wheat, respectively. Short-term beneficial effect of dung on maize yield was ascribed to its additional N supply. Urea and calcium ammonium nitrate (CAN) were equally good for both maize and wheat; full and split N application gave no significant difference in yield. The values for mean fertilizer N recovery over all the crops were 64, 58 and 44% respectively, at 60, 120 and 180 kg N per ha levels.Nitrogen application at the highest rate (180 kg per ha) reduced the soil pH significantly in the top 40 cm of the soil profile. The magnitude of soil acidification at levels of N below 120 kg per ha was not appreciable in this study. High N application also depleted the soil of its cations at differential rates. Other factors such as N source, time of N application and addition of dung along with N fertilizer did not have much influence on the rate of short-term soil acidification due to N fertilizer use.     

Nitrogen rate impacts on tropical maize nitrogen use efficiency and soil nitrogen depletion in eastern and southern Africa

Nutrient Cycling in Agroecosystems - Sub-Saharan Africa is facing food security challenges due, in part, to decades of soil nitrogen (N) depletion. Applying N fertilizer could increase crop yields...     

Yield and nitrogen use efficiency of winter wheat with different soil fertility

Nutrient Cycling in Agroecosystems - Both the existing soil fertility and fertilizer application have important influences on crop yield and nitrogen (N) use efficiency, but knowledge about their...     

Changes in nitrogen budgets and nitrogen use efficiency in the agroecosystems of the Changjiang River basin between 1980 and 2000

To investigate both the temporal and spatial changes in the nitrogen use efficiency (NUE) of agroecosystems in the different agricultural regions of the Changjiang (Yangtze) River basin, we constructed a nitrogen (N) budget by using a database of county-level agricultural statistics that was collected every 10 years from 1980 to 2000. Based on the mass balance model, we defined the NUE of agroecosystems as the proportion of all N inputs that are exported via the harvested crop biomass. According to our estimates, the mean total N inputs increased from 8.68 Tg N in 1980 to 13.4 Tg N in 1990 and to 19.8 Tg N in 2000 due to regional human activities. The proportion of anthropogenic new reactive N to the total inputs increased from 42% in 1980 to 68% in 2000 while the proportion of recycled N decreased. N from synthetic fertilizers was the largest contributor to the basin and dramatically increased to 12.23 Tg N in 2000, corresponding to a fivefold increase over that in 1980. While the amount of N from atmospheric deposition, biological N fixation, and recycled N varied slightly between 1980 and 2000, the proportion of N in harvested crops to the total N inputs decreased. Furthermore, the proportion of N lost by denitrification, volatilization, and riverine N transport, and that stored in soil increased between 1980 and 2000 as a result of intensified agricultural activities. It was found that the change pattern of the NUE differs both temporally and spatially. In the Sichuan basin and the plains in the middle and lower reaches that comprise the main agricultural regions of the Changjiang River basin, the NUE increased between 1980 and 1990; however, it dramatically decreased in almost the entire area between 1990 and 2000. On the other hand, in the mountainous and hilly regions of the lower Jinshajiang and Wujiang watersheds, the NUE decreased between 1980 and 1990 but increased between 1990 and 2000. As a result, the total amount of N transported to the surface waters from the agroecosystem reached 4.32 Tg N in 2000, showing a 2.4-fold increase over that in 1980. The export of riverine N increased, and the areas that exported large amounts of riverine N expanded widely from the Changjiang lower plain to the Changjiang middle plain and the surrounding areas between 1980 and 2000. It was apparent that the high rates of N fertilizer application were the most important factor that led to the dramatic decrease in NUE between 1990 and 2000.     

Increases in nitrogen use efficiency decrease nitrous oxide emissions but can penalize yield in sugarcane

Nutrient Cycling in Agroecosystems - Nitrogen (N) fertilization strategies focused on increasing nitrogen use efficiency (NUE) and decreasing nitrous oxide (N2O) emissions are important for...     

Influences of free-air CO2 enrichment (FACE), nitrogen fertilizer and crop residue incorporation on CH4 emissions from irrigated rice fields

To investigate the response of methane (CH₄) emissions to an elevated atmospheric carbon dioxide (CO₂) concentration (200?±?40???mol?mol^?1 higher than the ambient atmosphere), we performed a 4-year multi-factorial experiment at a subtropical rice paddy that contained sandy loam soil in the Yangtze River Delta from 2004 to 2007 using free-air CO₂ enrichment (FACE) technology. Our results revealed that the elevated atmospheric CO₂ increased the seasonal cumulative CH₄ emissions by 15?% on average during the 4-year period. The increase was insignificant and much weaker than the previous studies, which might be primarily attributed to the absence of a significant difference in the rice biomass between the two CO₂ levels in half of the field treatments. Crop residue incorporation hindered the stimulatory effects induced by the elevated CO₂, which were 37, 14 and 6?% for the fields that were incorporated with none, half or all of the wheat straws that were harvested in the preceding winter wheat season, respectively. Nitrogen fertilizers application also hindered the stimulatory effects of the elevated CO₂ on the CH₄ emissions. The CO₂ stimulatory effect was 39?% for the field without nitrogen fertilizers, and reduced to 17, 7 and 5?% for the field with nitrogen fertilization of 125, 250 and 350?kg?N?ha^?1, respectively. The regulation of nitrogen fertilizers on the CO₂ effects in this experiment does not well agree with the previous studies, which might because the soil type was different from those of the previous studies. Thus, further studies are necessary to evaluate the role of soil properties in regulating the effects of elevated atmospheric CO₂ on CH₄ emissions from managed and natural wetlands. There were no significant interactions between the atmospheric CO₂ and the incorporations of nitrogen fertilizer and crop residue. Appropriate experiments are necessary for better understanding of the interact influences of the elevated CO₂ and farm managements.     

Dynamics in input and output coefficients for land use studies: a case study for nitrogen in crop rotations

Increasingly, model-based approaches play a role in the design and development of new land use systems. Simulation modeling may play a role in the generation of land use systems for land units, and optimization modeling (e.g. linear programming – LP) may be used in the upscaling to farm and region. In the quantification of new land use systems for land units, often equilibrium conditions with respect to soil resources are assumed, following a so-called target-oriented approach. This facilitates ex ante computation of inputs and emissions of nutrients and allows their use in static optimization models based on LP. The condition of equilibrium in soil resources is often not met, nor is it the ultimate aim. Hence, the dynamics in new systems are insufficiently dealt with. This paper presents an approach for the design of land use systems (crop rotations) and their quantification in terms of input and output coefficients, using particular yields and dynamics in soil resources as targets. Interactions between N input and output of succeeding crops are explicitly taken into account. A simple N-balance model is used describing major processes affecting soil N-dynamics. For the Koutiala region in Mali five crop rotations are evaluated that differ in target crop yield, crop choice, crop residue management and external N source. Modeled crop rotations aiming at high yields, in combination with incorporation of crop residues and legumes, result in depletion of soil N stock. Only in crop rotations aiming at high yields and with incorporation of crop residues combined with a supply of large quantities of animal manure, soil N depletion can be prevented. Four approaches are presented of how to use the dynamic input–output coefficients of these systems in land use studies using LP: (i) use of average coefficients, (ii) use of discounted coefficients, (iii) use of pessimistic estimates of coefficients in an optimization of the land use allocation followed by a recalculation of the objective values for the optimized land use with optimistic coefficients, and (iv) a combined use of systems characteristics, i.e. cumulative N-inputs of land use systems over the time horizon and the magnitude of the soil N pool at the end of the time horizon, which can be used as filters for land use systems. Though none of the approaches completely captures the dynamics in input–output coefficients, they enable a well-founded consideration of the consequences of dynamics in, for instance, soil N stocks in static optimization approaches for farm and regional studies.     

Nitrogen-use efficiency and economic efficiency of slow-release N fertilisers applied to irrigated turfs in a Mediterranean environment

The effect of three fertilisers that delay the bioavailability of nitrogen (N) in the soil was compared with ammonium nitrate and a zero N control in two irrigated turfs in NE Portugal. The fertilisers used were: Floranid permanent 16-7-15 (slow-release, IBDU/Isodur fertiliser); Basacote plus 9M 16-8-12 (controlled-release fertiliser, copolymer ethylene acrylic); Nitroteck 20-8-10 (stabilized fertiliser, dicyandiamide as nitrification inhibitor + coating with polyterpene) and Nitrolusal (ammonium nitrate, 20.5% N), applied all at a rate of 120 kg N ha⁻¹. Nitrolusal was split into two fractions of 60 kg N ha⁻¹. Phosphorus (P) and potassium (K) rates were balanced among treatments by using superphosphate (18% P₂O₅) and potassium chloride (60% K₂O). The turf dry matter (DM) yield and N concentration in dry material were determined from several cuts of biomass throughout the growing season. Based on DM yield, N concentration in dry material and fertilisation costs, indices of N use efficiency and economic efficiency were estimated. Soil nitrate levels were monitored by using anion exchange membranes inserted directly into the soil. Basacote gave significantly lower DM yields than the other fertilised treatments. The apparent N recovery of Basacote was also the lowest. The results showed that Basacote released less N than that required for an adequate plant growth in the beginning of the growing season, hampered the flush of spring growth. Furthermore, the release period of this Basacote formulation, in the environmental conditions of these experiments, seemed to be longer than the length of the growing season. Nitroteck and Floranid yielded similar or even higher DM and apparent N recovery values than did Nitrolusal. The indices of economic efficiency ordered the fertilisers as Nitroteck > Nitrolusal > Floranid > Basacote or Nitrolusal > Nitroteck > Floranid > Basacote, if the costs of P and K fertilisers used to balance the P and K rates in the experimental design were, respectively, taken or not taken into account.     

Nitrogen balances and nitrogen use efficiency of intensive vegetable rotations in South East Asian tropical Andisols

Nitrogen fertilizer application rates in intensive vegetable production in (South) East Asia have increased exponentially over the past decades, including in the low income countries. While there have been reports of excessive N inputs from e.g. Vietnam, Thailand and Indonesia, very little quantitative knowledge exists on the real extent of the problem. We calculated N balances and agronomic N use efficiencies (ANUE) for a number of typical intensive vegetable rotations in the highlands of Central Java, Indonesia, on fertile Andisols, both for individual cropping cycles (short term) as for 6 consecutive cropping cycles (long term). This was done for farmers practice (FP) treatments, and improved practice (IP) treatments, where N fertilization was significantly reduced. Yields were in general similar in FP and IP, but tended to be slightly higher in IP, with some significant differences. Both the short and long term N balances were always positive and usually very high. Short term N balances ranged from 9 to 559 kg N ha⁻¹ and 219 to 885 kg N ha⁻¹ in IP and FP, respectively, while short term ANUE ranged from 8 to 67 and 4 to 39% in IP and FP, respectively. Long term N balances ranged from 627 to 1,885 kg N ha⁻¹ and 962 to 3,808 kg N ha⁻¹ in IP and FP, respectively, indicating a massive excess of N supply especially in FP. N balances can thus be drastically reduced with no negative impacts on yield, on the contrary. Soil mineral N in the 0–25 cm layer was in general not very high (6.5–38.8 mg N kg⁻¹ soil) and not systematically different between IP and FP, probably as a result of excessive NO₃ ⁻ leaching. Therefore, topsoil mineral N seems to have only limited indicator value under these conditions. Because denitrification losses in these soils are not very high, most N in excess of the crop requirements will be lost by leaching. Quantitative data on N balances as obtained here may be used to sensitize policy makers and farmers about the threat of current farming practices to the environment, and to improve economic performance.     

Modelling nitrogen dynamics in soil–crop systems with HERMES

Model runs with HERMES were performed over entire crop rotation cycles for two experimental sites on loamy and sandy soils in Germany with differently managed plots. The model was able to simulate soil water and nitrogen contents on the sandy plots of Müncheberg with an index of agreement (IA)  >0.8 and  >0.69. Crop growth and N-uptake was simulated well with IA values  >0.89 and  >0.75, respectively. For the loess site in Bad Lauchstädt model results for above-ground biomass, storage organ and N-uptake agreed well with observations over a 4-year rotation with IA values of 0.93, 0.94 and 0.71, respectively. Soil mineral nitrogen was significantly overestimated on the cropped plot (IA = 0.45) as well as on the black fallow plot (IA = 0.65) using the default initialization of the decomposable nitrogen pools from the organic matter content. Equilibration of the pools, using data from a neighbouring long term experiment, improved soil mineral nitrogen simulation to an IA of 0.72 for the cropped and 0.91 for the fallow plot. The long term model performance was investigated using data from 1903 to 2002 of four differently managed plots in Bad Lauchstädt. Soil organic carbon, derived from simulated nitrogen pools, showed acceptable results for the unfertilized plot, but a distinct underestimation on plots with farmyard manure application. Simulated historical winter wheat and potato yields were distinctly overestimated during the initial 50 years. Therefore, an adoption of crop parameters for older varieties is necessary. The index of agreement of 0.9 indicates that the annual weather impact on yield fluctuations was correctly reflected.