Agricultural nitrogen balance and water quality in the UK

Abstract. Nutrient balance calculations have been advocated as indicators of the risk of nitrate loss from agricultural land. To explore this concept, a spatially distributed UK agricultural nitrogen balance was derived using annually updated statistics. The mean UK N surplus for 1995 was 115 kg N ha^–1, made up of 51 kg ha^–1for arable land, 140 kg ha^–1 for agricultural grassland (excluding rough grazing) and an additional 14 kg N ha^–1for agricultural land from pig and poultry units. Nitrogen surpluses were greater in lowland grassland (mainly in western, wetter areas) than in arable areas. However nitrate concentrations in rivers were generally greater in arable areas. The relationship between N balance and nitrate leaching was very different for grassland and arable systems, and was also sensitive to climate, level of inputs and management practices. Nitrogen surplus was therefore weakly or even negatively correlated with river nitrate concentrations or loads. A positive correlation was found only where the comparison was restricted to grassland-dominated catchments. Nitrogen surplus calculations identified areas of very high livestock densities, which would be associated with increased risk of pollution. However their use in isolation as indicators of N leaching, or of progress towards mitigation, could be misleading especially if comparing areas differing in land use, climate or soil type.     

A review of farm-scale nutrient budgets for organic farms as a tool for management of soil fertility

Abstract. On organic farms, where the importation of materials to build/maintain soil fertility is restricted, it is important that a balance between inputs and outputs of nutrients is achieved to ensure both short-term productivity and long-term sustainability. This paper considers different approaches to nutrient budgeting on organic farms and evaluates the sources of bias in the measurements and/or estimates of the nutrient inputs and outputs. The paper collates 88 nutrient budgets compiled at the farm scale in nine temperate countries. All the nitrogen (N) budgets showed an N surplus (average 83.2 kg N ha^–1 yr^–1). The efficiency of N use, defined as outputs/inputs, was highest (0.9) and lowest (0.2) in arable and beef systems respectively. The phosphorus (P) and potassium (K) budgets showed both surpluses and deficits (average 3.6 kg P ha^–1 yr^–1, 14.2 kg K ha^–1 yr^–1) with horticultural systems showing large surpluses resulting from purchased manure. The estimation of N fixation and quantities of nutrients in purchased manures may introduce significant errors in nutrient budgets. Overall, the data illustrate the diversity of management systems in place on organic farms, and suggest that used together with soil analysis, nutrient budgets are a useful tool for improving the long-term sustainability of organic systems.     

Nitrate leaching from organic farms and conventional farms following best practice

Abstract. This paper compares nitrate leaching losses from organic farms, which depended on legumes for their nitrogen inputs (66 site years) with those from conventional farms using fertilizers under similar cropping and climatic conditions (188 site years). The conventional farms were within Nitrate Sensitive Areas in England, but sites following special practices associated with that scheme were excluded. Nitrate losses during the organic ley phase (including the winter of ploughing out) were similar (45 kg N ha^–1) to those from conventional long-term grass receiving fertilizer N inputs of less than 200 kg N ha^–1 (44 kg N ha^–1) and from the grass phase of conventional ley-arable rotations (50 kg N ha^–1). Losses from conventional grass receiving higher N inputs were greater than from organic or less intensive grass. Nitrate losses following arable crops averaged 47 and 58 kg N ha^–1 for the organic and conventional systems respectively, with part of the difference being due to the greater proportion of non-cereal break crops in the latter. Thus under similar cropping, losses from organic systems are similar to or slightly smaller than those from conventional farms following best practice.     

Soil phosphorus management and water quality: a UK perspective

Abstract. An increasing proportion of P reaching surface waters appears to be derived from agricultural land; apportioning the relative contribution to particular farming systems is not straightforward. The majority of farms in the UK operate on the basis of an annual agricultural P surplus, the size of which varies across different farm types. Particularly high values (>20kg ha^-1) are commonly associated with intensive-livestock production and the lower values (<10kg P ha^-1) with arable farms. The geographical divide between the predominance of arable cropping in the east and livestock enterprises in the west of the UK should result in an uneven pattern to the distribution of annual P surplus. The expected cumulative effects of this surplus should be a noticeable increase in total and extractable soil P concentrations, but this is not readily apparent. While evidence from experimental plots suggests a relationship between the concentration of available soil P and that present in drainage waters, extrapolating this information so that it can be useful at the scale of a whole catchment is difficult. The loss of P from agricultural land is controlled by factors which are independent of the size of the annual P surplus. The pattern of P cycling, together with the dominant loss pathways, differ greatly between livestock and arable farming systems. Proportioning the contributions that either increased soil erosion arising from changing agricultural practices or the cumulative effect of a P surplus have had upon P loss is a necessary prerequisite to effective management.     

Meeting the UK's climate change commitments: options for carbon mitigation on agricultural land

Abstract. Under the Kyoto Protocol, the European Union is committed to an 8% reduction in CO₂ emissions, compared to baseline (1990) levels, during the first commitment period (2008–2012). However, within the overall EU agreement, the UK is committed to a 12.5% reduction. In this paper, we estimate the carbon mitigation potential of various agricultural land-management strategies (Kyoto Article 3.4) and examine the consequences of UK and European policy options on the potential for carbon mitigation.
We show that integrated agricultural land management strategies have considerable potential for carbon mitigation. Our figures suggest the following potentials (Tg yr⁻¹) for each scenario: animal manure, 3.7; sewage sludge, 0.3; cereal straw incorporation, 1.9; no-till farming, 3.5; agricultural extensification, 3.3; natural woodland regeneration, 3.2 and bioenergy crop production, 4.1. A realistic land-use scenario combining a number of these individual management options has a mitigation potential of 10.4 Tg C yr⁻¹ (equivalent to about 6.6% of 1990 UK CO₂-carbon emissions). An important resource for carbon mitigation in agriculture is the surplus arable land, but in order to fully exploit it, policies governing the use of surplus arable land would need to be changed. Of all options examined, bioenergy crops show the greatest potential. Bioenergy crop production also shows an indefinite mitigation potential compared to other options where the potential is infinite.
The UK will not attempt to meet its climate change commitments solely through changes in agricultural land-use, but since all sources of carbon mitigation will be important in meeting these commitments, agricultural options should be taken very seriously.     

Changes in the soil phosphorus status of agricultural land in the Netherlands during the 20th century

The Netherlands has a high cumulative mean phosphorus (P) balance. In the 20th century, cumulative mean P surpluses were ca. 4500 kg P₂O₅/ha. The annual surpluses have levelled off because of manure application limits from 1984 onwards. We report the effect of soil type, land use, and manure policy on changes in soil P of fields in the Netherlands during the 20th century. We used data (>5 million soil P tests) from the soil analysis laboratory BLGG AgroXpertus. Our results show that soil P has increased on average to fairly high and high ratings. Differences between regions and between land use have remained high from the first records in the 1930s; on arable land the increase continued until the end of our study period while on grassland no changes are evident in the last decades. In general regions with high livestock density have high soil P status. Soil P increased in the order bulbfields < grassland < arable land < maize land < horticulture, and in the order loess < clay < peat < sand soils. Spatial variations in P values reflect more the market value of the crops and regional availability of animal manure than (fertilizer) recommendations. Manure policy since 1984 has resulted in increasingly tight restrictions on P application from manure and fertilizers, but the effects are not yet clearly reflected in changed trends in soil P.     

Soil management for Alfisols in the semiarid tropics: erosion, enrichment ratios and runoff

Abstract. Continuous cultivation of soils of the semiarid tropics has led to significant land degradation. Soil erosion and nutrient loss caused by high runoff volumes have reduced crop yields and contributed to offsite damage. We compared a number of soil management practices (tillage, mulch and perennial/annual rotational based systems) for their potential to improve crop production and land resource protection in an Alfisol of the semiarid tropics of India. Runoff and soil erosion were monitored and surface soil and sediment were analysed for nitrogen and carbon to determine enrichment ratios. Amelioration of soils with organic additions (farmyard manure, rice straw) or rotating perennial pasture with annual crops increased soil carbon and nitrogen contents and reduced runoff, soil erosion and nutrient loss. Soil erosion totalled less than 7 t ha^–1, but enrichment ratios were often greater than 2 resulting in up to 27 kg N ha^–1 and 178 kg C ha^–1 being lost in sediment. Up to an extra 250 mm of water per year infiltrated the soil with organic additions and was available for crop water use or percolation to groundwater. The results show that there are good opportunities for reducing degradation and increasing productivity on farms.     

The estimation of mineralization, immobilization and nitrification in nitrogen-15 field experiments using computer simulation

A combination of mathematical analysis and computer simulation, using parameters readily measured in a nitrogen-15 field experiment, is employed to determine rates of mineralization, immobilization and nitrification under a growing crop. The procedure also yields the proportion of crop nitrogen uptake occurring as ammonium and nitrate.
When applied to -results from grass lysimeters receiving 250 or 900 kg N ha^–1 a^–1 as ammonium nitrate, the analysis suggested that at 250 kgN ha^–1 a^–1 64–66% of crop nitrogen uptake was as ammonium; at 900 kg N ha^–1 a^–1 the figure was 43–49%. Nitrification at 250kgNha^–1 was only 13–19kgN ha^–1 over 160d while at 900 kg N ha^–1 between 191 and 232 kg N ha^–1 were nitrified.
The results suggested that the apparent inhibition of nitrification in grassland soils may simply reflect poor substrate competition by nitrifying bacteria. Finally, there was a suggestion that mineralization/immobilization was lower at the high fertilizer rate.     

Nitrogen and phosphorus management on Dutch dairy farms: legislation and strategies employed to meet the regulations

 The high input of nutrients through the use of fertilizers, manure and animal feed make it possible to reach high levels of agricultural production. However, high nutrient inputs may also result in large nutrient losses and thus have adverse effects on groundwater, surface water, and the atmosphere. To minimize nutrient emissions from agriculture, the Dutch government has introduced regulations on nutrient use. These include: (1) a ban on spreading animal manure on agricultural land during the winter, (2) the obligation to cover storage facilities for animal manure, (3) compulsory low-emission applications of animal manure to land, and (4) applying levies when the maximum permissible annual N and P surpluses for farms are exceeded. The nutrient surplus is the difference between nutrient input into the farm and nutrient output from the farm. The maximum permissible N surpluses for 2000 are 250 kg N ha^–1 year^–1 and 125 kg N ha^–1 year^–1 for grassland and arable land, respectively, and for P, 35 kg P₂O₅ ha^–1 year^–1 for both grassland and arable land. When the annual permissible levels are exceeded, farmers are charged with a levy. Results obtained at the experimental dairy farm "De Marke" showed that a reduction in nutrient inputs via fertilizers and purchased food, in combination with restricted grazing, reduced the N surplus in such a way that the NO₃ ^– concentration in the groundwater decreased to about the maximum permissible level of 50 mg NO₃ ^– l^–1. Since these results were obtained on a sandy soil that is very sensitive to NO₃ ^– leaching, it is suggested that all dairy farmers should be able to sufficiently reduce NO₃ ^– leaching by improving their farm management. Received: 13 July 1999     

N, P and K budgets for crop rotations on nine organic farms in the UK

Abstract. Nitrogen (N), phosphorus (P) and potassium (K) budgets were calculated for nine organic farms in the UK. The farms were situated on sandy loams, silty clay loams and silty loams over chalk with stockless farming systems and cattle, pig and poultry enterprises with a significant proportion of arable cropping. A soil surface nutrient budget was calculated for the target rotation on each farm using information about field management and measurements of the soil, crops and manure. Losses of N through leaching and volatilization were calculated independently using the nitcat and manner models. Nutrient budgets for seven of the farm rotations showed an N surplus, six a P surplus and three a K surplus. The ratio of N inputs supplied in the form of biological fixation : manure : atmospheric deposition was approximately 2 : 2 : 1 for stocked systems and 2 : 0 : 1 for stockless systems. Phosphorus surpluses resulted from supplementary P fertilizer (rock phosphate) and additional feed for non-ruminant livestock. The stockless system without P fertilizer resulted in a large P deficit and stocked systems, which relied on recycling manure alone, a small P deficit. Only rotations with large returns of manure or imported feed showed a K surplus or a balanced K budget.     

Nitrate leaching from reseeded pasture

Abstract. Nitrate leaching and soil mineral N status under grassland were measured on three contrasting soils, spanning winters 1995/96, 1996/97 and 1997/98, in Western England. The soils investigated were a freely draining silty clay loam (Rosemaund), a well drained loam (IGER 1) and a poorly drained clay loam (IGER 2). The effects of reseeding (ploughing and resowing grass) at IGER 1 and IGER 2 in autumn 1995 or 1996 were compared with undisturbed pasture. Reseeding at Rosemaund, in autumns 1995 or 1996, or spring 1996 was compared with undisturbed pasture of 3 sward ages (2, 5, >50 years).
Nitrate-N leaching losses during the winter immediately following autumn reseeding ranged between 60 and 350 kg N ha^–1 in 1995/96, depending on soil type, sward management history and rainfall. Losses were much less in the following winter when treatments were repeated (10–107 kg N ha^–1).
Reseeding in spring had little effect on soil mineral N content or leaching losses in the following autumn, compared with undisturbed pasture. Similarly, leaching losses from autumn reseeds in the second winter after cultivation were the same as undisturbed pasture (1-19 kg N ha^–1). The effect of ploughing grassland for reseeding was relatively short-term, in contrast to the effect of repeated annual cultivation associated with arable rotations.     

Carbon cycling and sequestration opportunities in temperate grasslands

Abstract. Temperate grasslands account for c. 20% of the land area in Europe. Carbon accumulation in grassland ecosystems occurs mostly below ground and changes in soil organic carbon stocks may result from land use changes (e.g. conversion of arable land to grassland) and grassland management. Grasslands also contribute to the biosphere–atmosphere exchange of non-CO₂ radiatively active trace gases, with fluxes intimately linked to management practices. In this article, we discuss the current knowledge on carbon cycling and carbon sequestration opportunities in temperate grasslands. First, from a simple two-parameter exponential model fitted to literature data, we assess soil organic carbon fluxes resulting from land use change (e.g. between arable and grassland) and from grassland management. Second, we discuss carbon fluxes within the context of farming systems, including crop–grass rotations and farm manure applications. Third, using a grassland ecosystem model (PaSim), we provide estimates of the greenhouse gas balance, in CO₂ equivalents, of pastures for a range of stocking rates and of N fertilizer applications. Finally, we consider carbon sequestration opportunities for France resulting from the restoration of grasslands and from the de-intensification of intensive livestock breeding systems. We emphasize major uncertainties concerning the magnitude and non-linearity of soil carbon stock changes in agricultural grasslands as well as the emissions of N₂O from soil and of CH₄ from grazing livestock.     

京郊畜禽粪肥资源现状及其替代化肥潜力分析

随着都市型规模化养殖业快速发展,畜禽粪尿废物大量排放因缺乏足够面积土地消纳所带来的环境压力很大,而粪尿中的氮磷钾养分与化肥一样对作物同等重要,如何合理利用这些废物资源决定了都市化农业的可持续发展。该文针对京郊养殖业和农用地面积现状,结合调研、收集畜禽养分排泄系数和农田养分需求等参数,估算京郊固液粪便养分资源现状及其替代化肥的潜力。结果表明:京郊畜禽固液粪便中N、P、K养分量分别为58.7×103、21.3×103、29.8×103 t,其中固体粪便N、P、K养分分别为43.1×103、20.3×103和19.7×103 t,京郊畜禽固液粪便可分别满足农田N、P、K养分需求量的99.3%、185.2%、62.7%。大部分区县粪肥中P养分产生量超过作物P需求量,粮田秸秆还田可带入的N、P、K养分分别为11.0×103、1.6×103和15.0×103 t,情景分析表明在秸秆还田条件下,按照磷素平衡原则估算本地区所能消纳的粪肥所带入N、P和K养分数量分别为18.3×103、9.9×103和10.3×103 t,同时需要补充N、K化肥分别为29.8×103和22.2×103 t,其余粪肥则需经过堆肥化处理并输往外地。经过堆肥处理,固体粪肥可提供的N、P、K养分分别下降了23%、11%和12%,外输固体粪肥堆肥可进一步减少农田氮磷负荷以及可能的环境风险。     

Subsidence rates and carbon loss in peat soils following conversion to pasture in the Waikato Region, New Zealand

Abstract. Drainage of peat soils for agriculture can lead to large carbon losses due to oxidation of peat. We estimated peat subsidence rates and total carbon losses, due to 40 years of dairy farming on a former peat bog, by measuring the thickness of peat and total carbon of farmland and of an adjacent unmodified peat bog above a marker tephra layer that was deposited about 200 AD. Subsidence rates averaged 3.4 cm yr^–1 (95% confidence interval of 3.2 to 3.5 cm yr^–1) and carbon loss averaged 3.7 t ha^–1 yr^–1 (95% confidence interval of 2.5 to 5.0 t ha^–1 yr^–1). On average, 63% of the subsidence was due to consolidation, with the remainder (37%) attributed to losses of organic matter due to peat mineralization.     

Simple phosphorus saturation index to estimate risk of dissolved P in runoff from arable soils

Abstract. There is increasing evidence that phosphorus has been accumulating in the surface horizons of agricultural soils to the extent that some soils represent a potential diffuse source of pollution to surface waters. The relationships between equilibrium phosphorus concentration at zero sorption (EPC ₀) of soil and a number of soil physicochemical variables were investigated in the surface layers of arable and grassland agricultural soils sampled from the Thame catchment, England. Soil EPC₀ could be predicted from an equation including soil test (Olsen) P, soil phosphate sorption index (PSI) and organic matter content (OM) (R²=0.88; P <0.001) across a range of soil types and land use. The simple index Olsen P/PSI was found to be a good predictor of EPC₀ (R²=0.77; P <0.001) and readily desorbable (0.02 m KCl extractable) P (R²=0.73; P <0.001) across a range of soil types under arable having soil organic matter contents of <10%.     

Revised estimates of the carbon mitigation potential of UK agricultural land

Abstract. The soil sequestration components of recent estimates of the carbon mitigation potential of UK agricultural land were calculated on the basis of a percentage change to the soil carbon stock present in the soil. Recent data suggest that the carbon stock of soil in UK arable land has been overestimated, meaning that potential soil carbon sequestration rates were also overestimated. Here, we present a new estimate of the carbon stock in UK arable land, and present revised estimates for the carbon mitigation potential of UK agricultural land. The stock of soil organic carbon in UK arable land (0–30 cm) is estimated to be 562 Tg, about half of the previous estimate. Consequently, the soil carbon sequestration component of each mitigation option is reduced by about half of previously published values. Since above-ground carbon accumulation and fossil fuel carbon savings remain unchanged by these new soil carbon data, options with a significant non-soil carbon mitigation component are reduced by less than those resulting from soil carbon sequestration alone. The best single mitigation option (bioenergy crop production on surplus arable land) accounts for 3.5 Tg C yr⁻¹, (2.2% of the UK's 1990 CO₂-carbon emissions), whilst an optimal combined land-use mitigation option accounts for 6.1 Tg C yr⁻¹ (3.9% of the UK's 1990 CO₂-carbon emissions). These revised figures suggest that through manipulation of arable land, the UK could, at best, meet 49% of its contribution to the EU's overall Kyoto CO₂-carbon emission reduction target (8% of 1990 emissions), and 31% of the greater target accepted by the UK (12.5%). Even these reduced estimates show a significant carbon mitigation potential for UK arable land.     

Leaching and balances of phosphorus and other nutrients in lysimeters after application of organic manures or fertilizers

Abstract. A long-term lysimeter experiment with undisturbed monoliths studied leaching behaviour and balances of phosphorus (P), potassium (K) and nitrogen (N) during a seven year crop rotation on four types of soil receiving inorganic fertilizers, manure and grass compost respectively. It was shown that application of manure did not lead to any direct change in nutrient leaching, unlike the application of fertilizers to soils of normal fertility. However, soil type considerably affected the nutrient concentrations in the drainage water.
Manure applied in amounts equal to the maximum animal density allowed by Swedish legislation slightly oversupplied P and N (0.5–3.5 and 18–38 kg ha⁻¹ y⁻¹ respectively) compared to the crop requirement and leaching losses for most of the soils. The relationship between lactate-soluble P in the topsoil and the concentrations of dissolved P in the drainage water was very strong. However the strength of this relationship was dependent on just one or two soils. P losses from a fertile sandy soil were large (1–11 kg ha⁻¹ y⁻¹) throughout the crop rotation and average crop removal (13 kg ha⁻¹ y⁻¹) plus the leaching losses were not balanced (average deficit 3–6 kg ha⁻¹ y⁻¹) by the addition of fertilizer, manure or grass compost. No decreasing trend was found in the P losses during seven years. However, the K deficit (average 26 kg ha⁻¹ y⁻¹) led to a significant reduction in the leaching trend from this soil. The other soils that had a smaller K deficit showed no significant reduction in the leaching of K.     

Denitrification in drained and undrained arable clay soil

Emissions of nitrous oxide (N₂O) and nitrogen gas (N₂) from denitrification were measured using the acetylene inhibition method on drained and undrained clay soil during November 1980-June 1981. Drainage limited denitrification to about 65% of losses from undrained soil. Emissions from the undrained soil were in the range 1 to 12 g N ha^–1 h^–1 while those from the drained soil ranged from 0.5 to 6 g N ha^–1 h^–1 giving estimated total losses (N₂O + N₂) of 14 and 9 kgN ha^–1.
Drainage also changed the fraction of nitrous oxide in the total denitrification product. During December, emissions from the drained soil (1.8±0.6 gN ha^–1 h^–1) were composed entirely of nitrous oxide, but losses from the undrained soil (2.7 ± 1.1 g N ha^–1 h^–1) were almost entirely in the form of nitrogen gas (the fraction of N₂O in the total loss was 0.02). In February denitrification declined in colder conditions and the emission of nitrous oxide from drained soil declined relative to nitrogen gas so that the fraction of N₂O was 0.03 on both drainage treatments. The delayed onset of N₂O reduction in the drained soil was related to oxygen and nitrate concentrations. Fertilizer applications in the spring gave rise to maximum rates of emission (5–12g N ha^–1 h^–1) with the balance shifting towards nitrous oxide production, so that the fraction of N₂O was 0.2–0.8 in April and May.     

Nitrate leaching following autumn and winter application of animal manures to grassland

Abstract. Under a UK Government consultation procedure announced in 2001, it was proposed that measures agreed within already designated Nitrate Vulnerable Zones (NVZ 's) would be extended to include a considerably increased area of England, Wales and Scotland. Since existing NVZ 's in the UK have included relatively little grassland, it is important to examine how nitrate losses from grassland areas, especially from animal manures, one of the major potential sources of nitrate loss, can be minimized. Experiments were carried out on freely draining grassland soils at four sites (Devon, Hampshire, Shropshire and N Yorkshire) representative of a wide range of climatic and farming conditions across lowland England, over a four year period, 1990/91 to 1993/94. Slurry was applied to experimental plots over a range of times (including June and then monthly, from September to January) at a target rate of 200 kg N ha^–1. Nitrogen leaching over the four years ranged from 0 to >50% of applied slurry N, with the largest losses occurring following applications in the September to November period. The use of a nitrification inhibitor with slurry applied in November failed to provide consistent reduction in nitrate leaching.
A strategy to reduce the risk of N leaching from manures applied to freely draining grassland soils must take account of the characteristics of the manure, in particular its N content, the application rate and the amount of excess rainfall following application. The experimental results suggest that slurry applications to freely draining grassland, in September, October and November should generally be avoided, the rationale for this being dependent on the amount of excess rainfall subsequent to application. Farmyard manure represents a lower risk and does not justify the restrictions on application timing that appear to be necessary with slurry.     

Use of long-term monitoring data to derive a relationship between nitrogen surplus and nitrate leaching for grassland and arable land on well-drained sandy soils in the Netherlands

The decrease in nitrogen (N) use in agriculture led to improvement of upper groundwater quality in the Sand region of the Netherlands in the 1991–2009 period. However, still half of the farms exceeded the European nitrate standard for groundwater of 50 mg/l in the 2008–2011 period. To assure that farms will comply with the quality standard, an empirical model is used to derive environmentally sound N use standards for sandy soils for different crops and soil drainage conditions. Key parameters in this model are the nitrate-N leaching fractions (NLFs) for arable land and grassland on deep, well-drained sandy soils. NLFs quantify the fraction of the N surplus on the soil balance that leaches from the root zone to groundwater and this fraction represents N available for leaching and denitrification. The aim of this study was to develop a method for calculating these NLFs by using data from a random sample of commercial arable farms and dairy farms that were monitored in the 1991–2009 period. Only mean data per farm were available, which blocked a direct derivation of NLFs for unique combinations of crop type, soil type and natural soil drainage conditions. Results showed that N surplus leached almost completely from the root zone of arable land on the most vulnerable soils, that is, deep, well-drained sandy soils (95% confidence interval of NLF 0.80–0.99), while for grassland only half of the N surplus leached from the root zone of grassland (0.39–0.49). The NLF for grassland decreased with 0.015 units/year, which is postulated to be due to a decreased grazing and increased year-round housing of dairy cows. NLFs are positively correlated with precipitation surplus (0.05 units/100 mm for dairy farms and 0.10 units/100 mm for arable farms). Therefore, an increase in precipitation due to climate change may lead to an increase in leaching of nitrate.