Context and objective Understanding the response of cereal yields to fertilizer nitrogen (N) is crucial in modelling food security within planetary boundaries, and in economic optimization of N use within environmental limits. Here we explore how agronomic N efficiency (N-AE, kg grain per kg N applied) in cereals depends on locally attainable yield (Ymax, highest yield observed per trial) and control yield (Y0, yield at zero fertilizer-N). Methods Data were collected from 593 N response trials with winter wheat and spring wheat (Triticum aestivum L.), spring barley (Hordeum vulgare L.), and spring oats (Avena sativa L.) in Denmark, the Netherlands, Spain, the UK and Sweden, giving 3268 N-AE data points. We applied linear mixed effect modelling to quantify the effects of N rate (NF), Ymax, Y0, and the ‘yield window’ ΔY (the difference Ymax-Y0) on N-AE. Results and Conclusions N-AE was largely governed by the yield window, besides the well-known effect of N rate. As such, the yield window captured effects of soil, year, cultivar and country on N-AE. Combined, ΔY and NF explained 80% (barley), 86% (winter wheat), 94% (spring wheat), and 91% (oats) of N-AE variance. Depending on crop species, a widening of ΔY by 1 t/ha raised N-AE by 4.7–6.5 kg grain per kg N, at N rates common in local practice. Substantial differences in mean N-AE at given N rate were found between data subsets by country. Economically optimal N rate (Nopt) varied widely between subsets, with averages of 175 kg N/ha (UK trials) and 215 kg N/ha (Swedish trials) at N-to-grain price ratio P = 3; or 156 and 200 kg/ha, respectively, at P = 6. Across trials, N-AE at Nopt responded linearly to ΔY by 5.0 (spring barley) and 3.2 (winter wheat) kg/kg per 1 t/ha increment of ΔY, independent of price ratio P. Significance The new concept of yield window provides opportunities for N optimization in modelling and practice. A larger yield window reduces N requirement per unit grain output well beyond reductions commonly associated with changes in yield potential in food security assessments. The newly presented N-AE model enables better estimation of N requirements to meet cereal production targets. It also enables a generic expression for optimal N rate as a function of yield window. Provided that control yield can be estimated, the model may contribute to more sustainable N management in cereals.

Decision support tools (DSTs) are crucial in aiding agricultural decision-making, particularly in improving soil health by enhancing nutrient management, soil organic matter (SOM) and water retention. Despite the availability of numerous DSTs in Europe, their adoption, effectiveness and development needs are not well understood, as most research is based on literature reviews rather than direct feedback from stakeholders. This study aims at filling this gap by conducting an expert survey of the most widely used digital DSTs across Europe on SOM, water retention and nutrient use efficiency in agriculture. We aimed at evaluating the current use, limitations and development needs of DSTs and offering recommendations to improve the effectiveness and adoption of DSTs in the context of soil health. A questionnaire was distributed to experts in 24 countries. Answers were received from 18 countries, including 14 European Union (EU) nations, Norway, the UK, Switzerland and Turkey. A total of 115 DSTs were identified aligning with our definition of DST, with agronomists, consultants and farmers being the primary users. Adoption of DSTs was rated moderate (score: 3.1/5), with tools featuring user-friendly interfaces and alignment with farmer goals achieving higher adoption rates. DSTs were rated better suited to achieve farm-level goals (score: 4.1/5) than regional (score: 3.6/5) or national objectives (score: 3.5/5). Major barriers to adoption included limited end-user involvement in DST development, which may hinder alignment with practical needs. Considering all the received questionnaires, the most frequently cited areas for improvement were nutrient use efficiency (45%), SOM (24%) and water retention (18%). Respondents emphasised the need for better integration of new farming systems (e.g., organic farming, agroforestry), more detailed process descriptions, integration of multiple processes, inclusion of economic modules and improved user interfaces. This study presents the first comprehensive evaluation of DSTs in Europe, revealing a diverse yet moderately adopted landscape. Increasing user engagement, enhancing technical integration and improving accessibility are essential for promoting a wider use of DSTs to improve soil health. By adopting these recommendations, DSTs can play a key role in achieving the EU's sustainability goals, fostering resilient agricultural systems and addressing environmental challenges such as soil degradation and climate change.

Soil health and climate change are increasingly impacting agriculture across Europe. Decision support tools (DSTs) have emerged as essential tools to help make accurate, evidence-based agricultural decisions aimed at enhancing productivity, profitability, and effective soil health management. Nevertheless, the adoption of these tools remains limited among farmers and varies across different regions. The aim of this study was to investigate, through a participatory approach, the challenges and drivers influencing the uptake and adoption of DSTs for sustainable soil management in Europe and Turkey. Our goal was to engage various stakeholders to identify the challenges and drivers associated with this process and collaboratively develop actionable recommendations to expand the application of DSTs. Multi-stakeholder workshops were conducted in Italy, Latvia, Sweden and Turkey, bringing together end-users, farmers, advisors, tool developers, researchers and policymakers from diverse agricultural contexts. The discussions during these workshops addressed the current use of DSTs, barriers to adoption, and potential solutions for scaling their use. The findings revealed that the primary barriers to adoption and scaling included costs, tool viability, data complexity, limited access to technical support, compatibility issues and insufficient marketing. To overcome these barriers and enhance the appeal of DSTs to users, stakeholders highlighted the necessity for user-friendly, affordable tools that offer enhanced transparency, real-time information, and adaptability to local farming conditions. Furthermore, stakeholders emphasised the importance of user-driven designs that could stimulate the innovation process and consider the interactions between human and technology. This study emphasises the complexity of adopting and scaling DSTs and the need for considering the local agricultural context. Stakeholder insights were categorised into a set of recommendations such as defining the scope of DSTs application, enhancing capacity building, creating a road map for stakeholders, and considering regional disparities in the participatory implementation process. A systematic, participatory approach is essential for addressing the different dimensions of the DST adoption and scaling process while taking into account regional differences in conditions and user needs.

Split nitrogen (N) application to oats delays final decisionson total application rate, which could help achieve the economic optimum fertilization rate (OptN) and reduce nitrogen losses. Later topdressing allows adjustment of fertilizer level at a stage when it is easier to predict nitrogen supply from soil. The objectives were: to investigate whether topdressing can be applied after stem elongation and to assess effects on yield and quality in different oat varieties; and to study the variation in optimum N-rate and the possibility to predict and readjust it during the growing season. In 14 field experiments conducted in Sweden 2020–2022, the effect of split nitrogen application, with topdressing at growth stage (GS) 32, GS45, or GS55–61, on yield and quality in six different oat varieties was evaluated. Late topdressing increased grain protein concentration and decreased fat content, but variety was more important for target quality. Compared with a single early application, late topdressing did not affect yield significantly. Year and site influenced yield and quality, similarly for all varieties, but had an impact on the effect N-treatment had on protein. A multiple regression analysis showed that yield at OptN and N-uptake in unfertilized plots at GS31–47, can explain the variation in OptN and thus be used to estimate OptN. Topdressing as late as at GS45–61 increased the chances both of higher protein and more accurate prediction of OptN. Therefore, recommendations for late topdressing can be preferable if there is a target for high protein or if there are incentives to use crop sensors for late and accurate adjustments of N fertilization rates between and within fields. The recommendations should not be dependent on variety.

IntroductionCattle slurry used as fertilizer in crop production is a mix of feces, urine, water, and bedding material from the housing system. Previous studies have shown that slurry nitrogen (N) availability to crops is dependent on C/N ratio. As the bedding material can contribute a significant part of total slurry carbon (C), its characteristics may affect the C/N ratio of the slurry. There is increasing interest in using the solid fraction from mechanical slurry separation as bedding material, and therefore this study investigated the potential effect of this fraction on slurry N availability, compared with more commonly used bedding materials such as straw and sawdust.MethodsIn two parallel 28-day laboratory incubations, net mineral N release and C mineralization from slurries applied to sandy loam soil were measured. The slurries comprised a liquid fraction (LF) from mechanical cattle slurry separation with a screw-press and different added bedding materials. Liquid fraction was mixed with two types of bedding material, solid slurry fraction (SF) and chopped straw, in different proportions, resulting in C/N ratios of 10, 12, and 14 in the slurry. In additional treatments, two other bedding materials, ground straw and sawdust, with slurry C/N ratio 12, were used.ResultsFor SF and chopped straw, similar negative linear correlations were seen between slurry C/N ratio and net mineral N release after 28 days. Carbon mineralization, expressed as a percentage of total C added, was higher from the mixture containing SF than that containing straw, while no clear relationship with C/N ratio was found. At slurry C/N ratio 12, net release of mineral N was 28–39% of total N and decreased in the order: sawdust>chopped straw=SF=ground straw. Net C mineralization at the same slurry C/N ratio was 33–46% and decreased in the order: SF=ground straw>chopped straw>sawdust.DiscussionFor bedding materials with similar fiber composition (i.e., SF and straw), differences in C availability due to particle size or degree of degradation by microorganisms did not influence slurry N availability measurably. For sawdust, with high lignin content, the results indicate that limited C availability may lead to lower slurry N immobilization.

Manure application performed in autumn requires regulation due to the risk of nitrogen (N) leaching during winter. On the other hand, application of manure in spring can pose some practical problems depending on the risk for N immobilization and the difficulty in ploughing heavy clay soils during this time of year. The risk for leaching is likely to differ between different soil texture and manure characteristics. In this study, we sought to estimate the risk for nitrogen leaching depending on the carbon/nitrogen ratio (C/N) of the manure, time for manure application, and soil type. We combined 3-year lysimeter experiments with 2-year field plot experiments and laboratory soil incubations and compared results with those from an empirical model. We compared effects of manure application on two soils (silty clay and loamy sand) and solid manures with different representing C/N ratios. In incubations, only manure with a C/N-ratio below 14 contributed with significant amounts of leachable N during the first months after application. In the lysimeter study, N leaching was unaffected by the timing of the application of the manure with C/N-ratio 18. However, regarding manure with C/N-ratio 10, N leaching was elevated with 10–15 kg N per ha after manure application in October compared to November and March on both soil types. The mineral N analyses from soil profiles in the field experiments showed a similar pattern, however, the increase was higher on the loamy sand compared to the silty clay. The ammonia emissions did not differ between manure types, but were on average 24% of applied NH4-N after application in October when air temperature was on average 12°C compared to only 3% of applied NH4-N in November and March when air temperature was on average 5°C. Similar to lysimeter results, the modelled N leaching was higher the earlier the manure application occurred in autumn. However, the model also predicted increased leaching for the manure with a high C/N-ratio, and a smaller effect on leaching on clay soil. Considering this, the model calculations overestimated the leaching effects from manure with a high C/N-ratio and underestimated the leaching effects on clay soil.

Animal slurry contains plant nutrients such as nitrogen (N) that are essential for crop production. Inorganic slurry N is easily volatilised as ammonia after field application, reducing slurry fertiliser value and causing environmental problems. Ammonia emissions can be reduced by lowering slurry pH, rapid infiltration or incorporation of slurry into soil. This study investigated the effect of different combinations of slurry types and application strategies on ammonia emissions. The slurry types tested were untreated cattle slurry (CS), the liquid fraction from mechanical solid-liquid separation of cattle slurry (LF) and biogas digestate based mainly on cattle slurry (BD). The application strategies tested were trailing hoses, trailing shoes, trailing hose application of acidified slurry and slurry injection. Ammonia emissions after slurry application were measured using wind tunnels, with continuous measurements of ammonia concentrations in outgoing air. Comparisons were also made between measured ammonia emissions and emissions predicted by the ALFAM2 model. Cumulative ammonia emissions after 70 h from LF, CS and BD represented 23%, 29% and 32% of total ammoniacal nitrogen (TAN) applied. Trailing shoes and 50 mm deep injection slots reduced ammonia emissions by on average 17% and 37%, respectively, compared with trailing hoses. Slurry acidification resulted in an average reduction in ammonia emissions of 83%. The ALFAM2 model was reasonably accurate in predicting cumulative emissions (70 h). Accuracy in predicting emission dynamics was low in some cases, likely due to differences between wind tunnel measurements and open-air emis-sions and to model error.(c) 2023 The Authors. Published by Elsevier Ltd on behalf of IAgrE. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Leaching of nitrogen from arable land can lead to pollution of groundwater and surface water. Various measures have been implemented in agriculture to reduce leaching, but there is still potential to do more. To find the best agricultural management regime to limit the problem, leaching from soils under different management must be measured. Different methods to estimate leaching are available, but they have not been thoroughly evaluated. This study compared (a) leaching of nitrogen from five different fertilizer treatments differing in amount and source (mineral and organic) of nitrogen and (b) two different methods for measuring leaching (tile‐drained field plots and lysimeters). Nitrogen leaching from five different fertilizer treatments was studied for three years in a tile‐drained field facility and for three of the treatments also for 16 months in a lysimeter facility. Leaching from organic and mineral nitrogen sources was similar in the three‐year field study. Mineral nitrogen input above the economic optimum tended to give greater leaching (by 24%–43%) than nitrogen input at the expected optimum. Measurements in lysimeters and tile‐drained field plots gave similar results, although leaching values tended to be slightly higher (by 18%–25%) in the tile‐drained field. Overall, both facilities give reliable estimates of nitrogen leaching and are suitable for leaching studies.

Nitrous oxide (N2O) is a strong greenhouse gas, and the emissions from managed soils are increasing. Emissions of N2O are highly variable in time and space, and there are potential triggers for emission peaks both in crop season and no-crop season. The aim of this study was to compare how fertilizer treatments, differing in rate and source of nitrogen (N), influence direct N2O emissions from soil, in crop season as well as in no-crop season, with the use of automated, high-frequency chamber measurements. Emissions were measured from cereal production on a Swedish clay-rich soil fertilized with biogas digestate, pig slurry and two levels of mineral N, as well as from control plots receiving no fertilizer N. The results showed that N2O emissions per unit area were low in all treatments, compared to other studies. Emissions from the treatment with mineral fertilizers at recommended rates were similar to the emissions from the control (0.65 and 0.48 kg N2O-N ha(-1) yr(-1), respectively). One-year cumulative emissions from a mineral N input rate 50 % higher than recommended were about three times higher than the control. Emissions of N2O from the pig slurry and biogas digestate treatments per unit area were of the same magnitude as from the high mineral N treatment. While the emissions from the high mineral N treatment were associated with elevated concentrations of nitrate in the drainage water, the high emissions from the organic fertilizer treatments were probably a result of large input of ammonium and degradable organic matter both in the year studied and in the preceding year. Most (approximately 75 %) of the N2O emissions occurred between harvest in autumn and sowing in spring, mainly in periods of freeze-thaw cycles. The relative differences between treatments were roughly the same during crop season and no-crop season. This study concludes that it is possible to combine high yields with very low N2O emissions -even on a clay soil in a semi-humid climate -when using mineral fertilizers at recommended rates.

Ammonia (NH3) emissions from land-applied liquid manure (slurry) contribute to nitrogen deposition, acidification, and formation of fine particles in the atmosphere. Optimal management and field application techniques can reduce emission. A reduction in contact area between the slurry and the atmosphere is expected to reduce NH3 emission. The objectives of this study were to develop a method for quantifying the exposed surface area (ESA) of field-applied slurry over time, and determine the degree to which ESA explains differences in NH3 emission. Two experiments were conducted in which untreated, separated, and digested slurry was applied in bands on two different soils with spring oats stubble. Emission data were obtained from online wind tunnel measurements and slurry characteristics such as surface pH, viscosity, and particle size distribution were measured. The new ESA method relies on fluorescent dye added to the slurry prior to field application, followed by imaging. The results show that the ESA measurements can give new insight into the soil-slurry interactions after manure application, and this may help explain why some types of slurry and application techniques lead to successful abatement under some circumstances, but not under others. Furthermore, a pH-, TAN-, temperature-, and ESA normalised NH3 emission were estimated, helping idetify the effects of infiltration. (c) 2020 IAgrE. Published by Elsevier Ltd. All rights reserved.

This study compared the effects on nitrate leaching of slurry application to ley in early autumn (15 September), late autumn (1 November) and spring (April) under Swedish growing conditions. In two separate two‐year experiments, started in autumn 2009 and 2010, on a sandy loam soil in south‐west Sweden, these three application times were compared with no slurry application in grass–clover and grass swards. Soil water was sampled with ceramic suction cups, and nitrate leaching was calculated from water nitrate concentrations and drain discharge. Plant measurements indicated that, during autumn, the grass took up at least 20 kg of the 50 kg nitrogen (N) applied with slurry in September. The mineral nitrogen level in the subsoil (30–90 cm) in December was around 2 kg N ha−1 higher in this treatment. Nitrate leaching was on average 5 and 6 kg N ha−1 year−1 higher after early and late autumn slurry application, respectively, than after spring application (p < .001), but the difference varied from 0 to 10 kg N ha−1 year−1 between experiments and sward types. Nitrate leaching losses in kg N ha−1 were lower from the grass sward, but higher if related to nitrogen inputs and dry matter yield. These results indicate that autumn application can increase the risk of nitrate leaching, but that early/late application within autumn is less important. It is more important to limit the amount of slurry applied in autumn and to consider other risks of nitrogen losses associated with time of application, such as ammonia emissions.

New technology makes it possible to apply organic fertilizers with higher precision, and organic producers want to know how to exploit these new possibilities to make their production more efficient. This study investigated the effect of band application (in different positions) of pelleted organic fertilizer, compared with broadcasting, on grain yield and weed density in spring oats (Avena sativa L.). Six microplot field experiments were carried out on silty clay and sandy loam in Sweden during the growing season of 2014-2016. In oats seeded at 25 cm row spacing, pelleted meat bone meal was band-applied at one of three distances from the crop row (0, 4, and 12.5 cm) and at two or three incorporation depths (1 and 4 cm on silty clay and 1, 4, and 6 cm on loamy sand). These treatments were compared with broadcast spreading, mineral nitrogen fertilizer, and an unfertilized control. On both soil types, fertilizer placement 4 cm from the crop and 4-6 cm incorporation depth gave the highest yield and crop nitrogen uptake. Yield in this treatment was 800 kg ha(-1) higher on clay soil and 1,100 kg ha(-1) higher on sandy loam compared with the same organic fertilizer applied by broadcasting, an 80-150% yield increase. On the sandy loam, distance from the crop row had a more significant effect on grain yield (p < 0.001) than soil incorporation depth (p = 0.07). On the silty clay, crop yield was significantly influenced by incorporation depth (p = 0.003) and distance from the crop row (p = 0.04). In five experiments, mineral N fertilizer equivalent (MFE) increased from on average 63% with broadcasting to 85% with placement 4 cm from the crop row and 4 cm incorporation depth. Weed biomass was significantly affected by fertilizer placement on the clay soil, with higher weed biomass with deeper incorporation (p = 0.045) and greater distance from the crop row (p = 0.049). On the sandy loam, there was a tendency for larger weed plants at greater distance from the crop row (p = 0.13) except when seeds and pellets were placed together, which gave the highest weed weight, probably due to lower competition from the crop in this treatment.

Agriculture represents 59 % of the anthropogenic nitrous oxide (N2O) emissions, according to the IPCC (Ciais et al. 2013). N2O emissions are typically irregular and vary widely in time and space, which makes it difficult to get a good representation of the emissions (Henault et al. 2012), particularly if measurements have low frequency and/or cover only a short time period. Manual measurements are, for practical reasons, often short-term and low-frequent, or restricted to periods where emissions are expected to be high, e.g. after fertilizing. However, the nature of N2O emissions, being largely unpredictable, calls for continuous or near-continuous measurements over long time periods. So far, rather few long-term, high resolution measurements of N2O emissions from arable fields are reported; among them are Flessa et al. (2002) and Senapati et al. (2016). In this study, we have a two-year data set (2015-2017) with hourly measurements from ten automatic chambers, covering unfertilized controls as well as different nitrogen fertilizer treatments. Grain was produced on the field, and effects of tillage, harvest and other cropping measures were covered.

Forskare vid SLU undersoker i pagaende forsok hur skorden paverkas av att placera pelleterad organisk godsel pa olika avstand fran saraden och att mylla den till olika djup. Preliminara resultat i havre visar att placering fyra centimeter fran raden och fyra centimeters myllningsdjup gav storst skord.

Fosforgodslingseffekten av femton potentiella godselmedel baserade pa restprodukter testades dels i krukforsok och dels i inkuberingsforsok. Mojligheten att relatera fosforeffekten till extraherbart fosfor med olika extraktionsmedel testades ocksa. I studien ingick bl.a. tre avloppsslam, tre sorters stallgodsel, tva rotrester, tre askor samt kott- och benmjol. I krukforsoket odlades rajgras som klipptes efter 5 och 11 veckor for att mata skord och fosforupptag. Tre kontrolled med olika nivaer av mineralgodselfosfor fanns ocksa med. Da fosfortillgangligheten ar starkt beroende av pH, testades effekten i krukforsoken i bade kalkad och okalkad jord for att sarskilja effekter av tillford fosfor fran eventuella kalkningseffekter av restprodukten. Resultaten visade att skord och fosforupptag hammades av kalkning i denna studie. Kalkverkande restprodukter hade darfor en samre effekt. Produkter med litet organiskt innehall, t.ex. askor och rotrester, hade en snabbare effekt an manga av de andra produkterna med storre organiskt innehall sasom stallgodsel och slam. Dessa skillnader jamnade ut sig med tiden. Sammanlagd skord och fosforupptag over 11 veckor var ganska lika for alla produkter och var i niva med det led som fatt halv dos med mineralgodselfosfor. P-AL talet i inkubationsforsoket okade ocksa ungefar halften sa mycket som med mineralgodsel. Men det fanns inget samband mellan vilka produkter som gav hogst effekt pa fosforskord och hogst P-AL. Det fanns daremot ett visst samband mellan extraherbart fosfor fran godseln och godselns effekt pa fosforskord, framfor allt vid den forsta klippningen. Bast fungerade P-AL-extraktion. Citratextraktion gav missvisande varden pa avloppsslam, men fungerade annars bra. Vattenextraktion innebar for lag extraktionsgrad i forhallande till vad som var vaxttillgangligt for flera produkter.

Organic inputs including livestock manures provide nitrogen (N) to crops beyond the year of their application. This so-called residual N effect should be taken into account when making decisions on N rates for individual fields, but also when interpreting N response trials in preparation of recommendations. This paper addresses general principles of residual N effects, gives literature-based estimates of them, and reviews to which extent residual N effects are included in recommendations and regulations in selected countries.

Hoga kvavegodslingsnivaer kan oka nitratutlakningen. Hur stor denna okning blir hanger troligtvis samman med grodans kvaveutnyttjande och godslingens effekt pa skorden. For att studera nitratutlakningen efter olika kvavegodslingsnivaer och skorderespons, anlades faltforsok i havre 2007, 2008 och 2009 pa en sandjord utanfor Skara i Vastergotland. Nitratutlakningen bestamdes fran nitratkoncentrationen i markvatten som provtogs med keramiska sugceller placerade pa 80 cm djup samt fran uppmatt avrinning vid en matstation i narheten. Resultaten visade att okningen i utlakning pa grund av godsling var obetydande sa lange godslingen gav en skorderespons pa atminstone 10 kg karna (85% TS) per kg tillfort kvave. Over denna godslingsnivaniva avtog skorderesponsen och nitratutlakningen okade gradvis. Detta innebar att utlakningen per producerat kg havre var som minst runt denna niva. Den ekonomiskt optimala kvavegivan beror pa prisrelationen mellan godsel och spannmal, vilken i Sverige vanligen varierar mellan 5 och 15. Med andra ord, precisionsgodsling som innebar 10 kg skordeokning per extra kg kvavegodsel kan vara optimal for ekonomin och ger samtidigt ingen okad kvaveutlakning.

Abstract The objective of this work was to test whether a dynamic soil C and N model using site-specific information improved estimates of apparent net N mineralization compared with regressions only based on static soil properties. This comparison was made using data from a 34-point sampling grid within a Swedish arable field during two growing seasons, using a simple carbon balance and nitrogen mineralization model (ICBM/N) for the dynamic approach. Three free model parameters were simultaneously optimized using non-linear regression to obtain the best model fit to the data from all grid points and both years. Calculated annual mean net mineralization (Nm_sim) matched the measured Nm mean exactly, and was 44 and 71 kg N ha−1 for the two growing seasons 1999 and 2000, respectively. However, the variability in calculated Nm_sim values among the 34 grid points was smaller than that measured, and only a small proportion of the variation within a single year was explained by the model. Despite this, the model explained 56% of the total variation in Nm during the two growing seasons, mainly due to the good fit to the seasonal overall difference. Significant factors influencing net mineralization included the soil environment controlling mineralization, total N in soil organic matter and N in crop residues. Uncertainties in estimation of θ fc and θ wp (soil water content at saturation and wilting point) and the possible influence of unknown horizontal and vertical water flows made high-precision calculations of soil water content difficult. The precision and general applicability of the actual measurements thus set limits for estimating critical parameters, and the limitations of both the experimental design and the model are discussed. It is concluded that improvements in precision in sampling and analysis of data from the grid points are needed for more critical hypothesis testing.