N Fertilizer Replacement Value Research Articles

Fertilizer replacement value and leaching of nitrogen applied to spring barley in cattle deep litter: A 3-year lysimeter study

On farms with intensive animal production, manure represents a significant source of nitrogen (N) in crop production. Cattle deep litter is a common manure type in Denmark due to concerns regarding animal welfare. With a low ammonium to total N ratio, large quantities of deep litter are needed to meet crop N requirements. However, documentation regarding the N fertilizer value of deep litter and its effects on nitrate leaching losses needs further scrutiny. We investigated the N fertilizer effect of cattle deep litter in the year of amendment and in two residual years, and determined nitrate leaching losses in the two seasons following amendment, both with and without use of a cover crop.Spring barley (Hordeum vulgare) grew in outdoor lysimeters (1 m2 and 1.5 m deep) with two soil types, a loamy sand and a sandy loam. Crop N uptake was measured after incorporation of two rates of deep litter (362 and 725 kg total N ha−1), and compared with uptakes following mineral N fertilizer. After harvest, the lysimeters were vegetation-free or established with a cover crop (fodder radish, Raphanus sativus). The residual effect of the treatments was monitored in two following seasons.In the year of amendment (2017), crop yields in deep litter amended lysimeters were similar to those obtained with mineral N fertilizer on sandy loam while yields were lower on loamy sand. The N effect of the deep litter equaled its ammonium content on the loamy sand while it was higher on the sandy loam. The corresponding N fertilizer replacement value (NFRV) of manure total N was 9.7% and 16.2%. In the first residual year (2018), NFRV of the deep litter was 9.5% on the loamy sand and 6.8% on the sandy loam. The third year (2019) effect was small on both soils. In the first autumn-winter, marginal nitrate leaching of N was unaffected by type of amendment. It equaled 8.1% of total N applied when lysimeters were without a cover crop and 1.4% with a cover crop. In the second leaching season, marginal nitrate leaching was 4.6% of total N applied in the previous year.We conclude that deep litter can supply spring barley with sufficient N for optimal growth and has a considerable residual effect in the year after amendment. Marginal nitrate leaching was unaffected by N source and soil type, and nitrate leaching losses can be effectively reduced by introducing a cover crop.

Nitrogen fertilizer replacement value of dairy soiled water in grass swards as affected by timing and rate of application

AbstractDairy soiled water (DSW) is a dilute mixture of cow faeces, urine, milk and detergents produced from the washing of milking plant and holding areas, and contains nutrients. Its N fertilizer replacement value (NFRV), compared to inorganic fertilizer (IF), was determined in a plot experiment on two grassland soils (well‐drained and poorly drained) in SW Ireland over a year with 4 N rates (0, 15, 22 and 30 kg N/ha), nine application timings and four replicates. Herbage was harvested at 4 and 8 weeks after each application to determine the total 8‐week DM yield. While caution is required, as results are based on only two sites and one year, DSW increased herbage production and showed potential to substitute for inorganic fertilizer N with surprisingly high NFRVs of 72 to 90%, potentially offering cost savings to farmers, improved N use efficiencies and reduced risk of nutrient loss to the environment. High NFRV may be due to factors such as the even spread and infiltration of DSW, low rates of ammonia emission or a stimulatory effect on the release of soil N. Yield increased significantly (p < .001) with N rate from approximately 1,200 kg DM ha−1 at 0 kg N/ha to approximately 1,700 kg DM ha−1 at 20–30 kg N/ha but application beyond approximately 20 kg N/ha was associated with increasingly diminished yield response. Yield response was greatest from March to July and poor response in winter suggests a greater risk of N loss during this period.

Effect of hairy vetch cover crop on maize nitrogen supply and productivity at varying yield environments in Southern Brazil

Cover crops play a critical role on conservation and sustainable agriculture due to their well-documented benefits on both soil and crop productivity. Inclusion of legumes (e.g., hairy vetch, Vicia villosa Roth) in the farming system can reduce the nitrogen (N) fertilizer needs for cereals such as maize (Zea mays L.) crop while maintaining or increasing its productivity. The aims of this research study were to quantify the effect of hairy vetch as a cover crop on: i) successor maize yield under varying yield environments (YEs) and fertilizer N rates, and ii) maize N status [N uptake, N nutritional index (NNI), and N fertilizer replacement value (NFRV)] at flowering time. Two field studies were carried out in Southern Brazil under varying YEs. The factors investigated were: YE (low, medium, and high), hairy vetch cover crop (with and without), and fertilizer N rate (0, 60, 120, 180, and 240 kg N ha−1). Under the combination of low YE and low fertilizer N rates (0–60 kg ha−1) with previous vetch, maize displayed the largest yield response and an improvement in its N status. The NNI determined at maize flowering was an efficient index of the vetch effect, increasing delta maize yield response (yield with- minus without-vetch) as the NNI reduced, with more than 10% delta yield response with NNI below 0.85. The NFRV of the hairy vetch represents potential N savings of 151 kg N ha−1 for the LYE, 95 kg N ha−1 for the MYE and from 59 to 45 kg N ha−1 for the HYE depending on the tested fertilizer N rate. The N coming from the legume cover crop in addition to the N fertilization was critical for supplying N to maize and boosting productivity across all YEs.

Nitrogen fertilizer value of animal slurries with different proportions of liquid and solid fractions: A 3-year study under field conditions

AbstractThe plant availability of manure nitrogen (N) is influenced by manure composition in the year of application whereas some studies indicate that the legacy effect in following years is independent of the composition. The plant availability of N in pig and cattle slurries with variable contents of particulate matter was determined in a 3-year field study. We separated cattle and a pig slurry into liquid and solid fractions by centrifugation. Slurry mixtures with varying proportions of solid and liquid fraction were applied to a loamy sand soil at similar NH4+-N rates in the first year. Yields and N offtake of spring barley and undersown perennial ryegrass were compared to plots receiving mineral N fertilizer. The first year N fertilizer replacement value (NFRV) of total N in slurry mixtures decreased with increasing proportion of solid fraction. The second and third season NFRV averaged 6.5% and 3.8% of total N, respectively, for cattle slurries, and 18% and 7.5% for pig slurries and was not related to the proportion of solid fraction. The estimated net N mineralization of residual organic N increased nearly linearly with growing degree days (GDD) with a rate of 0.0058%/GDD for cattle and 0.0116%/GDD for pig slurries at 2000–5000 GDD after application. In conclusion NFRV of slurry decreased with increasing proportion of solid fraction in the first year. In the second year, NFRV of pig slurry N was significantly higher than that of cattle slurry N and unaffected by proportion between solid and liquid fraction.

Nitrogen fertilizer replacement value of digestates from three green manures

Green manure mixtures including legumes and forbs can help to increase N availability in organic arable systems. Anaerobic digestion of green manures may provide ammonium rich digestate, which can be redistributed as fertilizer. The aim of this study was to investigate the effect of plant species composition, cutting strategy and anaerobic digestion on the N fertilizer replacement value (NFRV) of different green manures. Digestates obtained from silages of pure stand lucerne (four cuts/year) and a mixture including lucerne, grass and forbs (two or four cuts/year) were used to fertilize winter wheat (surface banding) and spring barley (injection). In general, NFRV was 46–173% higher in spring barley than winter wheat, due to the different application method and timing, which reflect the common practices in Denmark. NFRV of digestates were 25–63% higher than the corresponding silages, with the largest increase with the most fibrous material (mixture at two cuts/year). Total N concentration (DM based) in the silages largely explained NFRV of the digestates. To obtain NFRV above 60%, total N concentration of silage should exceed 3.5 g 100 g−1 DM, achievable with silages from four-cut strategies. Silages of plant materials with different composition and N content may be similar in terms of biomethane production, but the fertilizer value of the digestates varies considerably depending on total N concentration.

Effect of management and age of ploughed out grass–clover on forage maize yield and residual soil nitrogen

AbstractForage maize (Zea mays L.) is often grown year after year on the same land on many intensive dairy farms in north-west Europe. This results in agronomical problems such as weed resistance and decline of soil quality, which may be solved by ley-arable farming. In the current study, forage maize was grown at different nitrogen (N) fertilization levels for 3 years on permanent arable land and on temporary arable land after ploughing out different types of grass–clover swards. Swards differed in management (grazing or cutting) and age (temporary or permanent). Maize yield and soil residual mineral N content were measured after the maize harvest. There was no effect on maize yield of the management of ploughed-out grass–clover swards but a clear effect of the age of grass–clover swards. The N fertilizer replacement value (NFRV) of all ploughed grass–clover swards was >170 kg N/ha in the first year after ploughing. In the third year after ploughing, NFRV of the permanent sward still exceeded 200 kg N/ha, whereas that of the temporary swards decreased to 30 kg N/ha on average. Soil residual nitrate (NO3−) remained below the local, legal threshold of 90 kg NO3− N/ha except for the ploughed-out permanent sward in the third year after ploughing (166 kg NO3− N/ha). The current study highlights the potential of forage maize – ley rotations in saving fertilizer N. This is beneficial both for the environment and for the profitability of dairy production in north-western Europe.

Does acidification increase the nitrogen fertilizer replacement value of bio‐based fertilizers?

AbstractAcidification of manure, digestate and their processed derivatives has been proposed as a technique to, amongst others, mitigate ammonia emissions related to application in the field. The current study investigated whether acidification of (1) pig slurry (PS), (2) liquid fraction of pig slurry (LFPS), (3) digestate (DIG), and (4) liquid fraction of digestate (LFDIG) increases their nitrogen (N) fertilizer replacement value (NFRV) as compared to non‐acidified counterparts, a synthetic N fertilizer (calcium ammonium nitrate; CAN) and an unfertilized control. Product performance was evaluated from the perspective of (1) crop development (yield, nutrient uptake, and crop quality assessment) via a pot experiment with Lactuca sativa L. and (2) soil N dynamics [net N release (Nrel,net) and net N mineralization] via a soil incubation experiment. Crop yield of pots receiving bio‐based fertilizers performed ‘on par' with CAN as compared to unfertilized control, implying that bio‐based fertilizers derived from digestate or manure could potentially play a role in replacing synthetic N fertilizers. However, our findings also suggest that acidification did not result in an increased use efficiency of applied N. NFRVs of acidified products were below those of non‐acidified products and CAN, with crop yield on average 6–13% and 11–18% lower compared to non‐acidified products and the CAN treatment, respectively. A possible explanation for lower performance as compared to non‐acidified products could be an inhibitory delay in the Nrel,net, which in our experimental design proved to be negative for crops with short production cycles. This pattern was revealed in the incubation experiments in which Nrel,net in acidified products remained below that of non‐acidified, in this study tentatively attributed to immobilization of mineral N. However, this negative effect on N availability should be reaffirmed in crops with longer production cycles. Finally, some interesting findings with regard to plant composition also warrant further in‐depth investigation, e.g., Zn uptake by lettuce in acidified treatments was significantly higher than that of non‐acidified treatments. This implies that product pre‐treatment may play a future role in biofortification and amelioration of (trace) element composition of crops (arguably for crops with longer production cycles). Improving crop nutritional value by increased uptake of micronutrients is receiving increasing attention.

Nitrogen Fertilizer Replacement Value of Concentrated Liquid Fraction of Separated Pig Slurry Applied to Grassland

ABSTRACTSeven grassland experiments on sandy and clay soils were performed during a period of 4 years to estimate the nitrogen (N) fertilizer replacement value (NFRV) of concentrated liquid fractions of separated pig slurry (mineral concentrate: MC). The risk of nitrate leaching when applying MC was compared to when applying mineral fertilizers. Grassland yields in 2009–2012 fertilized with MC were compared with grassland fertilized with two mineral fertilizers: granulated calcium ammonium nitrate and liquid ammonium nitrate (LAN). The mineral fertilizers comprised 50% nitrate-N and 50% ammonium-N, and MC comprised 95–100% ammonium-N. Treatment application rates included zero N and three incremental rates of N fertilization. The liquid fertilizers were shallow injected (0–5 cm). The NFRV of MCs was 75% on sandy and 58% on clay soil with granulated ammonium nitrate as reference, and 89% on sandy and 92% on clay soil with LAN as reference. Risk of nitrate leaching after application of MC, measured in residual soil mineral N post-growing season and N in the upper groundwater in the following spring, was equal to that for mineral fertilizers.

Cover Crops, Fertilizer Nitrogen Rates, and Economic Return of Grain Sorghum

Leguminous cover crop systems have been envisaged as a critical component of sustainable agriculture because of their potential to increase soil productivity by cycling C and N in agricultural systems. Our objectives were to: (i) determine the effects of including summer cover crops and N rates in the cropping system on the growth and yield of the succeeding grain sorghum [Sorghum bicolor (L.) Moench] crop, (ii) calculate the N fertilizer replacement value (NFRV) and evaluate economic returns, and (iii) determine the most cost‐effective cropping system. Field experiments were conducted for two seasons in Kansas. Leguminous summer cover crops and double‐cropped soybean [Glycine max (L.) Merr.] residues improved soil N availability; N was subsequently used by the succeeding crop. Across years and cropping systems, the mean increases in grain yield as a result of including cowpea [Vigna unguiculata (L.) Walp.], pigeonpea [Cajanus cajan (L.) Millsp.], sunn hemp (Crotalaria juncea L.), double‐cropped soybean, and double‐cropped grain sorghum in the rotation compared with a fallow system with 0 kg N ha−1 were 56, 62, 43, 32, and 3%, respectively, and NFRVs across the years were 53, 64, 36, 27, and –3 kg N ha−1, respectively. Across years, grain sorghum in a double‐cropped soybean system and a fallow system with 90 kg N ha−1 gave profitable economic net returns. We conclude that including leguminous cover crops in a cropping system has the potential to reduce N requirements and improve the N availability and grain yield of the succeeding grain sorghum crop.

Effect of ensilaged vegetable crop residue amendments on soil carbon and nitrogen dynamics

Vegetable crop residues aid in maintaining soil quality and fertility, but pose a high risk of N-losses during autumn. Removal and conservation of these residues followed by a timely reapplication in spring may aid in synchronizing nutrient demand and availability. Crop residues of four vegetables were co-ensilaged with maize straw in a 1:1 ratio on volume base. Silage of leek and white cabbage were incubated with soil for measuring C and N mineralization and N fertilizer replacement value (NFRV). Vegetable crop residue silage promoted microbial activity when reapplied to the soil. This led to a temporary N immobilization up to 30% of the applied N after 14 days. A limited remineralization of up to +4% took place after 115 days which was confirmed by the positive NFVR. Nitrogen (N) losses during co-ensilage of vegetable crop residues were small and may help reduce N losses in intensive vegetable crop rotations during winter.

Nitrogen Fertilizer Replacement Value of the Liquid Fraction of Separated Livestock Slurries Applied to Potatoes and Silage Maize

Separation of livestock slurries followed by reverse osmosis yields mineral concentrates (MCs) in which almost all nitrogen (N) is ammonium (NH4)-N. The ability of MCs to substitute calcium ammonium nitrate (CAN), a common conventional mineral N fertilizer, was tested in two trials on a silty loam soil (ware potatoes, 2009 and 2010) and four trials on sandy soils (starch potatoes, 2009 and 2010; silage maize in 2010 and 2011). The N fertilizer replacement value (NFRV) of spring-injected MCs ranged from 72 to 84%, slightly less than their share of ammonium-N (90–100%). The fate of N that was apparently unavailable to crops was not fully disclosed, but there were indications that ammonia loss may have played a role.

Residual Effects of Fertilization with Pig Slurry: Double Cropping and Soil

Intensive pig (Sus scrofa domesticus) production is an important economic activity in the northeast of Spain. Pig slurry (PS) is applied annually to maize (Zea mays L.) fields and supplemented with mineral N fertilizer at sidedressing. Fertilization with PS at different rates during four consecutive years was evaluated for its effects on soil salinity, water‐stable aggregates (WSA), and crop response of two consecutive barley (Hordeum vulgare L.) and maize crops. We observed that the fertilization of maize with PS for four consecutive years did not increase soil salinity compared with mineral fertilization. We observed, however, an improvement in soil stability, which was measured by WSA, under PS fertilization (WSA = 16.0 ± 6.9%) compared with mineral fertilization (WSA = 5.6 ± 2.4%). The agronomic residual effect of the PS treatments on the barley crop was quantified in terms of the N fertilizer replacement value (NFRV) as 77 kg N ha−1 and was not associated with PS rates applied during the previous 4 yr. For the maize crop, a significant N residual effect was also detected; the NFRV ranged between 11 and 56 kg N ha−1 and was significantly related to the PS rates applied the previous years. These results indicate that the annual application of PS to sprinkler‐irrigated maize at agronomic rates does not induce soil salinization, can have beneficial effects on some soils by increasing aggregate stability, and can provide significant amounts of N to subsequent crops. It is important to consider residual N effects in fertilizer planning to avoid N losses from the system.

Nitrogen Fertilizer Replacement Value of Cattle Slurry in Grassland as Affected by Method and Timing of Application

Slurry application with methods such as trailing shoe (TS) results in reduced emissions of ammonia (NH3) compared with broadcast application using splashplate (SP). Timing the application during cool and wet weather conditions also contributes to low NH3 emissions. From this perspective, we investigated whether reduced NH3 emissions due to improved slurry application method and timing results in an increase in the nitrogen (N) fertilizer replacement value (NFRV). The effects of application timing (June vs. April) and application method (TS vs. SP) on the apparent N recovery (ANR) and NFRV from cattle slurry applied to grassland were examined on three sites over 3 yr in randomized block experiments. The NFRV was calculated using two methods: (i) NFRV(N) based on the ANR of slurry N relative to mineral N fertilizer; and (ii) NFRV(DM) based on DM yield. The TS method increased the ANR, NFRV(N), and NFRV(DM) compared with SP in the 40- to 50-d period following slurry application by 0.09, 0.10, and 0.10 kg kg(-1), respectively. These values were reduced to 0.07, 0.06, and 0.05 kg kg(-1), respectively, when residual harvests during the rest of the year were included. The highest NFRV(DM) for the first harvest period was with application in April using STS (0.30 kg kg(-1)), while application in June with SP had the Slowest (0.12 kg kg(-1)). The highest NFRV(DM) for the cumulative harvest period was with application in April using TS (0.38 kg kg(-1)), while application in June with SP had the lowest (0.17 kg kg(-1)). Improved management of application method, by using TS instead of SP, and timing, by applying slurry in April rather than June, offer potential to increase the NFRV(DM) of cattle slurry applied to grassland.

Performance, economics, and adoption of cover crops in Wisconsin cash grain rotations: On-farm trials

AbstractCover crop performance depends largely on management factors that must be customized to particular farm situations and, therefore, is suited for on-farm research, with farmers involved in both management and evaluation. Cover crop sequences that were successful in a research station study were tested over a variety of soils and management strategies in collaboration withfarmers. The two-year cover crop sequences consisted of a short-season crop followed by a cover crop in year one and corn in year two. The cover crops themselves were evaluated by their agronomic and economic performance and their acceptance by farmers. Four cover crop systems (companionseeded red clover, sequentially seeded hairy vetch, sequentially seeded oat, and fallow) were compared for ground cover, above-ground biomass and above-ground nitrogen yield, subsequent corn grain yield, and N fertilizer replacement value (N-FRV). Cover crops were essential for erosion control following vegetable crops and tillage, but were not necessary following small grains. Companion-seeded red clover produced the most ground cover, yielded up to 133 kg N/ha, and had a higher average N-FRV than sequentially seeded hairy vetch on sandy loam soils, but was not preferred by farmers who harvested small grain straw as well as grain. Sequentially seeded hairy vetch gave excellent cover when no-till seeded, produced more than 125 kg N/ha in half the siteyears, and had a higher average N-FRV than companion-seeded red clover on silt loam soils. First-year N-FRV for the legume cover crops averaged 67 kg N/ha over both soil types. The participating farmers indicated that their decisions to adopt cover crops would be based primarily on their need for ground cover, and secondarily on the profitability of using cover crops as an N source. However, when valued solely as an N source for the next year's crop (and not for any potential long-term benefits), cover crops were not an economical alternative to N fertilizer. We suggest focusing future cover crop research and extension efforts on outreach to farmers growing crops that do not provide sufficient ground cover, such as short-season vegetable crops, and optimizing the cover crop system to maximize its erosion control benefits and increase its profitability over N fertilizer.

N credit of soybean to a following corn crop in central Ontario

Field studies were conducted to determine the nitrogen (N) fertilizer replacement value (NFRV) when soybean (Glycine max [L.] Merrill) preceded corn (Zea mays L.) in the rotation (S-C), compared to corn preceding corn (C-C). Large, replicated blocks of soybean and corn were established in 1993 and 1994 near Elora, Ontario. In the following year, each large block was subdivided into smaller plots. Fertilizer N was applied at six rates from 0 to 200 kg N ha−1 to the second-year corn crop. Corn grain yield responses to fertilizer N were fitted by quadratic regression. Maximum economic rate of N was calculated for each crop sequence and NFRV's were determined. Corn yields were consistently higher when grown after soybean (S-C) than after corn (C-C). Maximum corn yields were 10.4 and 12.3 Mg ha−1 in 1994 and 1995, respectively. NFRVs for S-C, compared to C-C, were 41 and 59 kg N ha−1 in the two years. As a result of these studies and numerous other experiments, recommended fertilizer N rates have been changed to 30 kg N ha−1 less for S-C than for C-C in central Ontario. Key words: Nitrogen credit, corn, soybean, fertilizer N, replacement value, crop rotation

Forage corn dry-matter yields and N uptake as affected by previous legumes and N fertilizer

Field experiments were conducted in 1987 and 1988 on a Rivière-du-Loup sandy gravelly loam (Ferro-Humic Podzol) at St-Anselme and on a Chaloupe silty loam (Orthic Humic Gleysol) at Deschambault in Eastern Quebec. In monoculture, or following a legume, corn (Zea mays L.) Pioneer 3979 was fertilized with 0, 50, 100 or 150 kg N ha−1, and faba bean (Vicia faba L.) Outlook and soybean (Glycine max [L.] Merr.) Maple Amber received 20 kg N ha−1 as NH4NO3. In 1987, the whole-plant dry-matter yields (DMY) of corn increased linearly with the supply of N at St-Anselme and Deschambault. The stover and whole-plant N uptake, also increased linearly with the N levels at both locations, but the supply of N had no effect on the ear N uptake. In 1988, at St-Anselme and at Deschambault, the ear, stover and whole-plant DMY of plants not receiving N and following faba bean were significantly higher than those in monoculture or following soybean and not fertilized with N; these differences between previous crops were more evident at St-Anselme than at Deschambault. At both locations, the DMY of the stover, ears and whole plants of corn were more responsive to the increased N levels following soybean or corn. At both locations, the N uptake of corn following faba bean did not increase with the N levels in contrast to corn following corn or soybean. The N-fertilizer replacement values (NFRV) for soybean (on the basis of corn DMY) were negligible or lower than 0 kg N ha−1 at both locations. At St-Anselme, the values for faba bean were higher than 150 kg N ha−1, but averaged 32 kg N ha−1 at Deschambault (DMY basis). On the basis of corn N uptake, the NFRV of faba bean ranged from 92 kg N ha−1 for ears and was higher than 150 kg N ha−1 for whole plants at St-Anselme, and varied from 37 kg N ha−1 for stover to 44 kg N ha−1 for ears at Deschambault.Key words: Previous crop, forage corn, soybean, faba bean, N-fertilizer replacement value