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Controlled drainage with subirrigation (CDSI) is a viable measure to supply, retain or discharge groundwater, thereby contributing to freshwater availability in agriculture under changing environmental conditions. Relatively simple CDSI systems can be controlled manually to set a few drainage levels. More advanced systems can be controlled remotely to set any drainage level (between a technical maximum and minimum). CDSI potentially improves hydrological conditions for crop growth, but the required external water supply can be large. Therefore, the objective of this paper is to investigate whether external water supply for subirrigation can be reduced by automatic control of CDSI systems in relation to crop water demand. Field measurements of a CDSI pilot in the Dutch sandy Pleistocene uplands were combined with weather forecasts to simulate the optimal drainage level and day by day water demand and supply using the agro-hydrological Soil, Water, Atmosphere, Plant model (SWAP). Firstly, model simulations showed that the water requirement reduced by 60 mm (dry growing season), 253 mm (average growing season) and 348 mm (wet growing season) using a dynamically managed crest level (CDSI-dyn) compared to using a fixed crest level (CDSI-fix), with minor effects on crop yield. Secondly, model simulations showed that a higher hydraulic resistance to downward seepage, a higher ditch water level or deeper roots reduced the water supply (up to 100 mm). Thirdly, accepting 10 % daily crop drought and oxygen stress for CDSI-dyn reduced the water supply requirement with 235–628 mm (dry vs wet growing season) compared to CDSI-fix. In conclusion, the required water volume for CDSI could be substantially reduced by automated control of the drainage level and water supply rate, while maintaining crop yield or accepting minor reductions, which increases the potential of implementation of CDSI systems.

Groundwater extractions may cause drought damage to agricultural crops. In the Netherlands, drought damage is determined within the influence area of groundwater extractions. The AdviesCommissie Schade Grondwater (ACSG) uses a groundwater decline of 5 cm as boundary value of the influence area. Considering the developments of groundwater models and data, the question came up whether the boundary value could be moved from 5 to 2 cm. This article describes the hydrological aspects of determining groundwater decline due to groundwater extractions. The conclusion is that a 5 cm groundwater level decline is still a sound boundary value., Grondwateronttrekkingen kunnen droogteschade veroorzaken aan landbouwgewassen. In Nederland wordt droogteschade vastgesteld binnen het invloedsgebied van grondwateronttrekkingen. Daarvoor hanteert de AdviesCommissie Schade Grondwater (ACSG) een grondwaterstanddaling van 5 cm als grens. Gezien de ontwikkelingen in grondwatermodellen en databeschikbaarheid rees de vraag of de grens verlegd kan worden van 5 naar 2 cm. Dit artikel beschrijft de hydrologische aspecten van het vaststellen van verlagingen door grondwaterwinning. De conclusie is dat 5 cm grondwaterstanddaling nog steeds een verantwoorde grenswaarde is.

Irrigation and fertilisation are often over-applied, which exceeds crop requirements. Surface fertigation, a technique of applying pre-dissolved fertilisers together with irrigation water, seems to be a viable way to improve the on-farm performance in the North China Plain (NCP). Thus, we conducted a field experiment based on farmers’ practices from 2017 to 2019. Moreover, we calibrated and validated SWAP-WOFOST-N, a seasonal integrated agro-hydrology and crop growth model, to assess the effects of different practices on yield, water and nitrogen use efficiency (WUE and NUE) and resource loss. Lastly, we developed various scenarios using the model to determine improved strategies. The results showed that the SWAP-WOFOST and extended Soil-N model offered satisfactory accuracy when compared with field measured data for the tested domain of the hydrological and nitrogen cycle; farmers’ current irrigation and fertilisation practices resulted in low WUE and NUE, but the practice of split top-dressing nitrogen did not show significant improvement in the surface irrigation system; WUE, NUE and nitrogen loss were closely related to irrigation practices. We further concluded that an optimised irrigation practice combined with an optimal fertigation scenario is the feasible strategy to achieve sustainable crop yield, high WUE and NUE and reduced nitrogen loss.

Agricultural soils are at risk of nitrogen (N) leaching especially during the fallow period in autumn and winter. Cover crops are grown to capture soil mineral N that otherwise would leach to the groundwater. They can serve as green manure providing mineral N to the cash crop in spring. We investigated whether mixing species of cover crops can enhance N capture and therefore reduce N leaching more effectively than pure stands in autumn without increasing the risk of N leaching in spring. We hypothesised that mixed species with complementary traits will capture more N and accumulate more biomass. It was also expected that residues from cover crops with higher biomass and lower C:N ratio would mineralise faster and subsequently increase N leaching in spring. In a 4-year field experiment, cover crops were grown between August and February in a rotation with different cash crops. We used eight cover crop treatments, including three pure stands: radish (Raphanus sativus), vetch (Vicia sativa) and oats (Avena strigosa), all possible 2- and 3-species mixtures and a fallow (no cover crop). Treatment effects on leaching losses were estimated by analysing N concentrations in samples of leached pore water below the rooting zone and by modelling the volume of water leached per plot. Most N leaching occurred in autumn and winter while the amount of N leached in spring was negligible due to the lower precipitation. N leaching in autumn correlated negatively with cover crop biomass, N uptake and root length density. Radish and oats were the most productive species and dominated mixtures. Compared to the fallow, radish and mixtures that contained radish reduced N leaching by 49–73% and were characterized by quick soil cover, high N uptake and low to moderate C:N ratio. Subsequently, residues from radish and mixtures containing radish mineralized quickly, resulting in an increase in soil mineral N in spring by 70–110% as compared to fallow. This mineral N did not leach in spring and

Voldoende zoet water is noodzakelijk voor waterafhankelijke sectoren als landbouw, natuur, drinkwaterbedrijven en industrie. Zelfs in laaggelegen gebieden als Nederland wordt de disbalans tussen watervraag en wateraanbod steeds groter, naarmate waterbeheer, watergebruik en klimaat verder veranderen. Dit artikel is een samenvatting van een peer-reviewed artikel waarin een overzicht is gegeven van de veranderde drainagepraktijk in Nederland, met name vanontwikkelingen in gebruik en ontwerp van buisdrainage tussen 1950-2020: van water afvoeren, naar afvoeren én vasthouden en afvoeren én vasthouden én aanvullen. Op basis van Nederlandse veldproeven met regelbare drainage met subirrigatie en internationale literatuur, geven we inzicht in de componenten van de waterbalans die beïnvloed worden door drainage en subirrigatie. Op basis hiervan geven we een doorkijk naar of en hoe regelbare drainage met subirrigatie ingepast kan worden in het regionale watersysteem.

Sufficient freshwater is needed for water dependent sectors such as agriculture, nature, drinking water, and industry. However, even in low-lying, flood prone countries like the Netherlands, climate change, weather extremes, economic growth, urbanization, land subsidence and increased food production will make it more complex to guarantee sufficient freshwater for all sectors. Furthermore, the frequency and amplitude of extremely dry and wet weather conditions is expected to increase. The current Dutch water management system is not designed to anticipate these extremes. Over the last decades, drained Dutch agricultural fields, land consolidation and urbanization resulted in declining groundwater tables. Additionally, the fresh water demand of different sectors (agriculture, industry, drinking water) increased, causing an increased pressure on the regional groundwater system. As a consequence, the annual groundwater table in sandy soil areas dropped over time with the effect that, nowadays, fresh water is becoming scarce in dry periods. In this paper we provide insight in the shifting water management strategy in the Netherlands (1950–2020), with the corresponding drainage systems, developing from conventional drainage (approx. 1950–1990), to controlled drainage (1990’s onwards), climate adaptive drainage (2010 onwards) and subirrigation systems (2018 onwards). Furthermore, we provide insight in the effect of subirrigation on groundwater levels and crop yields, based on both international literature and measurements of Dutch field pilots. Although subirrigation can contribute to improved soil moisture conditions for crop growth on field scale, we show that the water volume needed for subirrigation can be large and could put a significant pressure on the available regional water sources. Therefore, efficient and responsible use of the available external water sources for subirrigation (e.g. surface water, treated waste water, or groundwater) is required. Finally, the

To address the problem of water scarcity and to achieve food self-sufficiency, huge efforts and massive irrigation developments have been made in the last twenty-five years by the Ethiopian Government. However, the performance of many small-scale irrigation (SSI) schemes is still very poor. Deficient irrigation water management is one of the major factors challenging the success and the sustainability of the SSI. Farmers are constrained by inappropriate irrigation management strategies, which result in irrigation water scarcity, yield loss and undesirable environmental impacts in most SSI. The issue of sustainability is given hardly attention.This thesis tries to assess, understand and evaluate the current irrigation water management practices in relation to crop yield and soil salinization and then come-up with simple and innovative irrigation water management strategies that can influence the farmers’ decision and enable them to cope with the problem of water scarcity and soil salinity.In Chapter 2 farmers’ irrigation water management practices, challenges, perceptions and adaptation were studied. We evaluated farmers survey data, field observations and measurements and found that the farmers’ perception of the major causes for aggravating water scarcity, crop yield decline and soil salinization were in line with field observations. The overall plot level and scheme level adaptation strategies of the farmers were not good enough. The farmers are constrained by lack of technical knowledge, weak enforcement capability of the Water Users Association (WUA) and poor irrigation infrastructures to manage the irrigation water properly at plot as well as at scheme level.The government involvement on sustainability of irrigation schemes is poor. Also, the top-down approach by local government authorities has been constraining the farmers’ adaptation strategies. The study showed that allowing beneficiaries to make their own decision resulted in innovative drought adaptation

Agricultural use of pesticides may result in contamination of groundwater being used as a drinking water source. Additionally, the emission of these compounds via drainage into surface waters can adversely affect aquatic ecosystems. Pesticide risk assessment is applied to evaluate the potential for health and ecological effects of a pesticide and is commonly performed using mechanistic models. Pesticides currently used in agriculture are soluble in water. Hence, both pesticide transport and water flow through the soil must be studied together through an environmental risk assessment of pesticides.Water flow and pesticide transport can be described for field conditions as uniform or preferential. While uniform flow leads to stable wetting fronts parallel to the soil surface, preferential flow generates unstable wetting fronts, differences in water pressure and solute concentrations, and rapid flow through parts of the soil matrix. This Ph.D. research project focuses on one source of preferential flow; macropore flow. Macropore flow produces fast vertical water flow and pesticide transport in a small soil volume, bypassing the reactive soil matrix. One effect of this is that some of the applied pesticides cannot degrade in the soil and instead arrives in groundwater or surface waters, negatively affecting water quality. Therefore, mechanistic models must incorporate macropore flow in pesticide risk assessment to ensure accurate simulations.Macropores are originated mainly by biological activity, drying and wetting cycles, and shrinking clays, which results in natural variation of the number of macropores in time and space. Some macropores directly end within the soil matrix, referred to as ‘dead-end macropores.’ We have designated the spatial variation of macropores over depth as ‘heterogeneous macropore geometry.’Dual-permeability models such as HYDRUS and SWAP are conventional mechanistic models utilized in pesticide risk assessment studies. The parametrization of t

Pesticide transport simulation by SWAP–PEARL (Soil–Water–Atmosphere–Plant and Pesticide Emission Assessment at Regional and Local scales) models can help to predict pesticide leaching at regional scales. For reasons of economic and time efficiency, measurement efforts should be prioritized towards critical parameters. The objective of this research is to perform a Morris screening and Sobol–Jansen sensitivity analysis to SWAP–PEARL models, using a reasonable worst-case scenario. Three pesticide compounds were analyzed:, bentazon (zero sorption), imidacloprid (moderately sorbed), and compound I (highly sorbed). Initial macropore and pesticide parameter values were varied by ±20% to generate parameter ranges. The outputs analyzed were the concentration in drainage water, the average concentration in groundwater between 1 and 2 m, and the concentration in the soil system at 100-cm depth. Influential parameters found through the Morris method were analyzed using the Sobol–Jansen method. The results for bentazon indicate that the degradation half-life (DT50), the bottom depth of the internal catchment (zic), and the proportion of the internal catchment at the soil surface (pic_0) are critical parameters in all the outputs analyzed. For imidacloprid and compound I, the most relevant parameters for drainage output are the Freundlich sorption exponent (Fexp) and zic; for groundwater, the relevant parameters are Fexp, the bottom depth of static macropores (zst), and pic_0; and for soil concentrations at 100-cm depth, the relevant parameters are Fexp, zic, and pic_0. The Morris and Sobol–Jansen methods produce the same results for the first position in the ranking. Measurement efforts should be performed to update national soil databases, including critical pesticide and macropore parameters.

Indonesian peatlands are critical to the global carbon cycle, but they also support a large number of local economies. Intense forest clearing and draining in these peatlands is causing severe ecological and environmental impacts. Most studies highlighted increased carbon emission in the region through drought and large-scale fires, further accelerating peatland degradation. Yet, little is known about the long-term impacts of human-induced disturbance on peatland hydrology in the tropics. Here we show that converting natural peat forests to plantations can significantly alter the hydrological system far worse than previously recognized, leading to amplified moisture stress and drought severity. This study quantified how human-induced changes to Indonesian peatlands have affected drought severity. Through field observations and modelling, we demonstrate that canalization doubled drought severity; logging and starting plantations even quadrupled drought severity. Recognizing the importance of peatlands to Indonesia, proper management, and rehabilitating peatlands remain the only viable option for continued plantation use.

Soils have many functions, such as producing crops, filtering water by binding nutrients and solutes, serving as a carbon pool and providing a habitat for all kinds of soil fauna. Soil quality can be assessed using easily obtainable soil information, such as soil maps and visual soil evaluation (VSE). The aim of this thesis is to evaluate whether easily obtainable soil information (soil maps and visual soil evaluation) can be used to assess soil functions. To reach the thesis aim and to bridge the knowledge gaps, three research questions were formulated: 1) to what extent does the required spatial scale in nutrient balances depend on the level of soil variation, 2) to what extent are quantitative visual soil observations reproducible, and do they correlate with standard field or laboratory measurements, and 3) can quantitative visual soil observations be used to assess soil functioning? This thesis thereby contributes to the assessment of soil quality in agricultural land, which can contribute to environmentally sustainable crop production. After the general introduction (Chapter 1), Chapter 2 discusses the role of spatial scales in nutrient balances on dairy farms. On five Dutch dairy farms, field level nitrogen (N) and phosphorus (P) balances were associated with soil series that were obtained from a 1:50.000 soil map. It is concluded that nutrient balances at field level are more informative than nutrient balances at the crop or farm level, which is relevant for decision making aiming to reduce nutrient losses to the environment. Chapter 3 uses quantitative visual observations in VSE. The two aims of this Chapter were to assess the reproducibility of quantitative visual observations, and to evaluate the correlation of quantitative visual observations with standard field or laboratory measurements. The reproducibility study and the validation study show that quantitative visual soil observations are moderately reliable, given the high probability that systematic e

Poor irrigation scheduling practices have been quoted as the major challenges for sustainability of small-scale irrigation schemes in Ethiopia due to complexity of scheduling techniques, cost and inaccessibility of soil-water monitoring tools, lack of various local climatic data and soil-water parameters. For local experts to easily schedule irrigation and to promote adoption by farmers, a cheap and simple computation procedure of irrigation scheduling is needed that considers local resources and opinions. So far, there is no such study in the context of Ethiopia. A simple irrigation scheduling method (Practical) was developed based on the FAO procedure (Brouwer et al., 1989), employing Hargreaves ET 0 equation and the opinions of local farmers and extension agents. Then, the method was validated on-farm through participatory and close observation of farmers by comparing with CropWat simulated (Sophisticated) and local (Traditional) scheduling practices for 2015and 2015/16 irrigation seasons considering maize as indicator crop. Data on irrigation depths, yield and yield components and soil salinity were collected and analysed. Furthermore, a farmers’ day was arranged to collect opinions on the crop stand and scheduling techniques. In both irrigation seasons, the practical irrigation schedule method resulted in higher grain yield while saving substantial amount of water and in significantly higher water productivity (WP) compared to the other methods. Maximum (0.68 kg m −3 in 2015) and minimum (0.47 kg m −3 in 2015/16) WP were found in the practical and sophisticated approaches, respectively. The average root zone salinities among the alterative irrigation scheduling methods were not significantly different, in both irrigation seasons. Farmers’ and experts’ opinions were in favour of the practical scheduling method. The practical irrigation scheduling method is thus recommended for maize, around Gumselassa area. Further, the presented procedure can be adopted for pre

Policy makers and farmers use tools, such as a nutrient balance, to gain insight into the environmental impact of agricultural practices. A discrepancy, however, exists between the needs of policy makers and farmers, about the use and the spatial scale of such tools. Farm balances calculate nutrient balances across all agricultural fields within a farm without distinguishing separate fields, whereas field balances calculate a nutrient balance on a delineated field. For farmers, a nutrient balance at field level is more useful than at crop or farm level, because decision making and fine-tuning management occurs at the field level. A field balance, however, requires more detailed data than a farm balance and therefore is less easy to implement. As soil types influence nutrient balances, we hypothesize that if within-farm variation in soil types is low, there is no need to replace a farm balance by a field balance. To test this hypothesis, we computed nutrient balances at farm and field level on five Dutch dairy farms (three on sand, two on clay), varying in degree of within-farm variation in soil series. A full year of soil nitrogen (N) and phosphorus (P) input and output data on farm and field level were provided by farmers, while soil variation was determined using the Dutch 1:50.000 soil map. The Annual farm Nutrient Cycle Assessment (ANCA) was used to calculate soil N and P surpluses, and soil nutrient fluxes such as nitrate leaching and nitrous oxide emission at farm and field level. Even on farms with few soil series, a considerable variation in N and P inputs, outputs and balances across fields was found, due to management differences and soil properties not represented by the soil map. Furthermore, field-level balances better represented nitrogen leaching than farm-level balances on farms with diverse soils (reflected by different leaching factors) and negative nitrogen field balances (deficits). Also, using field balances, for one case study farm the highest

With only 2.5% of the water on Earth available as fresh water, the security of its supply to feed a growing poplation will become increasingly uncertain. Global institutes try to find means to improve the distribution and security of water and food. Agriculture uses 70% of available fresh water which makes it by far the largest consumer of the limited amounts of fresh water. Water resources are finite and there is a need for new approaches to deal with increasingly complex water and food issues. Land and water management can contribute significantly to a sustainable increase of food security when based on modelling and monitoring in the soil water and plant domain. Field scale experiments are needed to test new theories for their correctness and added predictive value with the soil water balance as a central core to explain impacts and changes of crop growth. Contribution of upward vertical water flow to roots is an essential part of the water balance and an important driver for transpiration of crops. A physical approach to quantify this vertical water flow should therefore be compared with more simplified approaches and be quantified using field experimental data. The focus of this thesis is on vertical water flows. To be able to produce sound water balances actual yields have to be modelled, because actual transpiration is directly related to actual dry matter production. This in turn requires the ability to simulate actual crop growth and the need to account for actual water and crop management. Nowadays modelling is common practice to analyse experiments at different scales, ranging from field to global scale. The natural domains described in this thesis require extensive field tests and verifications at different scales. This thesis contributes to a better understanding of soil-water-plant interactions and to more advanced modelling of process-oriented approaches. It intends to provide an answer to four research questions : What is the role of the vertical wat, Dit proefschrift draagt bij tot een beter begrip van de interacties tussen de bodem-waterplant systemen en tot meer geavanceerde procesgerichte modelmatige benaderingen. Bovendien wordt antwoord gegeven op vier onderzoeksvragen: 1. Wat is de rol van de verticale waterstromen zoals capillaire opstijging en recirculerend percolatiewater op de gewasopbrengsten? 2. Hoe kunnen we droogte-, zout- en zuurstof-stress modelleren en wat is hun invloed op de gewasopbrengsten? 3. Kunnen we de impact van verschillende stress-vormen op de graslandproductie in Nederland voorspellen? 4. Wat is de invloed van veranderingen in grondwaterstanden en landgebruik op gewasopbrengsten en grondwateraanvulling?

Upward soil water flow is a vital supply of water to crops. The purpose of this study is to determine if upward flow and recirculated percolation water can be quantified separately, and to determine the contribution of capillary rise and recirculated water to crop yield and groundwater recharge. Therefore, we performed impact analyses of various soil water flow regimes on grass, maize and potato yields in the Dutch delta. Flow regimes are characterized by soil composition and groundwater depth and derived from a national soil database. The intermittent occurrence of upward flow and its influence on crop growth are simulated with the combined SWAP-WOFOST model using various boundary conditions. Case studies and model experiments are used to illustrate the impact of upward flow on yield and crop growth. This impact is clearly present in situations with relatively shallow groundwater levels (85 % of the Netherlands), where capillary rise is a well-known source of upward flow; but also in free-draining situations the impact of upward flow is considerable. In the latter case recirculated percolation water is the flow source. To make this impact explicit we implemented a synthetic modelling option that stops upward flow from reaching the root zone, without inhibiting percolation. Such a hypothetically moisture-stressed situation compared to a natural one in the presence of shallow groundwater shows mean yield reductions for grassland, maize and potatoes of respectively 26, 3 and 14 % or respectively about 3.7, 0.3 and 1.5 t dry matter per hectare. About half of the withheld water behind these yield effects comes from recirculated percolation water as occurs in free-drainage conditions and the other half comes from increased upward capillary rise. Soil water and crop growth modelling should consider both capillary rise from groundwater and recirculation of percolation water as this improves the accuracy of yield simulations. This also improves the accuracy of the simulated

It remains unclear if quality of life (QoL) improvements could be expected in young patients after malignant bone tumour surgery after 2 years. To assess the course of QoL over time during a long-term follow-up, malignant bone tumour survivors of a previous short-term study were included. Assessments were done at least 5 years after surgery. QoL was measured with Short-form (SF)-36, TNO-AZL Questionnaire for Adult's Quality of Life (TAAQOL)

Theory description and user manual

Detailed physical models describing root water uptake (RWU) are an important tool for the prediction of RWU and crop transpiration, but the hydraulic parameters involved are hardly ever available, making them less attractive for many studies. Empirical models are more readily used because of their simplicity and the associated lower data requirements. The purpose of this study is to evaluate the capability of some empirical models to mimic the RWU distribution under varying environmental conditions predicted from numerical simulations with a detailed physical model. A review of some empirical models used as sub-models in ecohydrological models is presented, and alternative empirical RWU models are proposed. All these empirical models are analogous to the standard Feddes model, but differ in how RWU is partitioned over depth or how the transpiration reduction function is defined. The parameters of the empirical models are determined by inverse modelling of simulated depth-dependent RWU. The performance of the empirical models and their optimized empirical parameters depends on the scenario. The standard empirical Feddes model only performs well in scenarios with low root length density R, i.e. for scenarios with low RWU “compensation”. For medium and high R, the Feddes RWU model cannot mimic properly the root uptake dynamics as predicted by the physical model. The Jarvis RWU model in combination with the Feddes reduction function (JMf) only provides good predictions for low and medium R scenarios. For high R, it cannot mimic the uptake patterns predicted by the physical model. Incorporating a newly proposed reduction function into the Jarvis model improved RWU predictions. Regarding the ability of the models to predict plant transpiration, all models accounting for compensation show good performance. The Akaike information criterion (AIC) indicates that the Jarvis (2010) model (JMII), with no empirical parameters to be estimated, is the “best model”. The proposed mod

For calculating the effects of hydrological measures on agricultural production in the Netherlands a new comprehensive and climate proof method is being developed: WaterVision Agriculture (in Dutch: Waterwi-jzer Landbouw). End users have asked for a method that considers current and future climate, that can quantify the differences between years and also the effects of extreme weather events. Furthermore they would like a method that considers current farm management and that can distinguish three different causes of crop yield reduction: drought, saline conditions or too wet conditions causing oxygen shortage in the root zone.WaterVision Agriculture is based on the hydrological simulation model SWAP and the crop growth model WOFOST. SWAP simulates water transport in the unsaturated zone using meteorological data, boundary condi-tions (like groundwater level or drainage) and soil parameters. WOFOST simulates crop growth as a function of meteorological conditions and crop parameters. Using the combination of these process-based models we have derived a meta-model, i.e. a set of easily applicable simplified relations for assessing crop growth as a function of soil type and groundwater level. These relations are based on multiple model runs for at least 72 soil units and the possible groundwater regimes in the Netherlands. So far, we parameterized the model for the crops silage maize and grassland. For the assessment, the soil characteristics (soil water retention and hydraulic conductivity) are very important input parameters for all soil layers of these 72 soil units. These 72 soil units cover all soils in the Netherlands. This paper describes (i) the setup and examples of application of the process-based model SWAP-WOFOST, (ii) the development of the simplified relations based on this model and (iii) how WaterVision Agriculture can be used by farmers, regional government, water boards and others to assess crop yield reduction as a function of groundwater characteris