Matches in SemOpenAlex for { <https://semopenalex.org/work/W200089869> ?p ?o ?g. }
- W200089869 abstract "The fact that conventional agricultural practices have many detrimental effects is widely acknowledged (Rabbinge, 1997). To mitigate these effects, Dutch policy makers have implemented environmental laws that are essentially based on characteristic indicators for groundwater quality. This has resulted in progressively tighter restrictions on the input of N fertilisers and a consistent reduction of the number of registered pesticides. Enforcement of these laws still creates considerable problems, which is partly caused by their generic character: no provision is made for the significant variation among soil types. As this variation is well known to farmers, their affinity with the imposed rules and regulations is limited. This thesis follows a different approach, in which soil variability is placed at the starting point of research, using the techniques of precision agriculture. The objectives are:Develop a methodology that efficiently describes soil variability at the within-field level. Soil variability should be described in terms of functional properties that are directly relevant to farm management operations. In other words: describe soils in terms of their water regimes, nutrient cycling and sorption characteristics rather than using traditional taxonomic properties such as texture, soil organic matter (SOM) content and colour.Based on the above, develop methods to: (i) optimise the application of N fertiliser and (ii) evaluate and control the environmental risks associated with pesticide use. These methods should be developed through prototyping (Vereijcken, 1997) with ample attention for operational aspects.In line with the desired setting, research was conducted on a commercial arable farm in the central-western part of the Netherlands (51 o 17'N, 4 o 32'E). The farm covers an area of approximately 100 ha and applies a crop rotation of winter wheat, consumption potatoes and sugar beet. Soils originate from marine deposits, are generally calcareous and have textures ranging from sandy loam to clay. They are characterised as fine, mixed, mesic Typic Fluvaquents (Soil Survey Staff, 1998) or Mn25A-Mn45A on the Dutch 1:50,000 soil map (Vos, 1984). Soil variability is large and mainly expressed through differences in texture, soil organic matter (SOM) content and subsoil composition (peat or mineral matter). Drainage conditions are excellent and in general terms the area is considered prime agricultural land.In order to fully exploit the potential of precision agriculture, an understanding is required of the biophysical processes that govern the growth conditions of a crop. Simulation models provide a powerful tool in this respect and play a crucial role throughout this thesis. To maximize the accuracy of modelling results, much effort was invested in producing high-quality input data. Four methods were compared to derive soil hydraulic parameters from the basic soil properties collected in a 1,5000 soil survey of the study area. Applied methods included: (A) laboratory measurements, (B) class pedotransfer functions, (C) continuous pedotransfer functions and (D) continuous pedotransfer functions combined with simple laboratory measurements. Modelling performance was evaluated by comparing simulated and measured soil moisture contents for three sites and two depths. The combination of continuous pedotransfer functions and simple laboratory measurements (method D) clearly produced best results. Modelling performance was highest overall and results were consistent for individual profiles and depths. Modelling uncertainty was lowest, far lower than the uncertainty resulting from the measured data set. (Chapter 2)With the soil hydraulic parameters available, attention focused on describing soil variability. Soils were characterised in terms of simulated functional properties relating to water regimes and nutrient dynamics. Four properties were considered: water stress, N-stress, N-leaching and residual N-content at harvest. Sensitivity to water stress was evaluated for a dry year (1989); other properties were quantified for a wet year (1987). Based on functional similarity, individual soil profiles were grouped into functional classes. Standard interpolation techniques and a boundary detection algorithm subsequently identified soil functional units in each field. Analysis of variance revealed that over 65% of the spatial variation could thus be accounted for. This confirmed that soil characterisation had been efficient and that the resulting units were suitable entities to be used as management units for precision agriculture. (Chapter 3)Once the management units had been established, two field experiments were conducted to compare precision and conventional N management. The experiments were conducted in consecutive years (1998 and 1999) and on different winter wheat fields ( Triticum aestivum L.). Precision management used real-time simulations to monitor soil mineral N levels in each management unit. Early warning was provided when mineral N concentrations dropped below a critical threshold. Used as a trigger , this information served to optimise the timing of four consecutive N fertilisations. Fertiliser rates were determined through exploratory simulations, which calculated the amount of mineral N required under normal conditions. Compared to conventional management, fertiliser input was reduced by 15-27% without affecting grain yield. Grain quality was either not affected (1999) or significantly increased (1998; P d the environmental threshold of 0.1 μg l -1 . Out of a total of 19 pesticides, the risk assessment identified isoproturon, metribuzin and bentazon as relatively high-risk for leaching. Risk levels differed strongly, with isoproturon presenting the lowest risk and bentazon presenting the highest risk. Soil variability strongly affected leaching at the within-field, field and farm levels. Spatial variability was highest for isoproturon, followed by metribuzin and bentazon. Opportunities for precision management were apparent, but depended on the scale level (within-field, field or farm level) at which the environmental threshold is implemented. When legislation is formulated on this issue, the presented step-wise evaluation can serve as a basis for identification and precision management of high-risk pesticides. (Chapter 6)To synthesize the above, the various studies were discussed in terms of their implications for environmental regulations on groundwater quality. A clear distinction was made between environmental threshold concentrations (50 mg l -1 for nitrate; 0.1 μg l -1 for pesticides) and proxy measures that are used to enforce these thresholds. Proxy measures applied in the Netherlands include maximum N fertilisation rates and a list of registered pesticides. Simulation results indicated that these measures cannot guarantee that environmental threshold concentrations are not exceeded. Their generic character presents a problem, as different soils show quite different behaviour in terms of N and pesticide dynamics. Feasible alternatives to proxy measures are not likely to be found within the context of conventional arable farming. Precision agriculture, however, does present realistic prospects to increase control over nitrate and pesticide emissions. In future it may well be worth to stimulate the introduction of precision agriculture, especially in areas where groundwater is used as a source of drinking water. (Chapter 7)" @default.
- W200089869 created "2016-06-24" @default.
- W200089869 creator A5081111645 @default.
- W200089869 date "2002-01-01" @default.
- W200089869 modified "2023-09-24" @default.
- W200089869 title "Soil processes as a guiding principle in precision agriculture" @default.
- W200089869 cites W1254864279 @default.
- W200089869 cites W1504649384 @default.
- W200089869 cites W1519102913 @default.
- W200089869 cites W1523762035 @default.
- W200089869 cites W1527588570 @default.
- W200089869 cites W1547526949 @default.
- W200089869 cites W1557321585 @default.
- W200089869 cites W1563220993 @default.
- W200089869 cites W1642724957 @default.
- W200089869 cites W1653652436 @default.
- W200089869 cites W1671932900 @default.
- W200089869 cites W1876282212 @default.
- W200089869 cites W1963872206 @default.
- W200089869 cites W1964174102 @default.
- W200089869 cites W1974927411 @default.
- W200089869 cites W1984846076 @default.
- W200089869 cites W1995450389 @default.
- W200089869 cites W2012269605 @default.
- W200089869 cites W2014765212 @default.
- W200089869 cites W2019264578 @default.
- W200089869 cites W2020691586 @default.
- W200089869 cites W2021920696 @default.
- W200089869 cites W2025214434 @default.
- W200089869 cites W2032600630 @default.
- W200089869 cites W2038669746 @default.
- W200089869 cites W2046114125 @default.
- W200089869 cites W2046139462 @default.
- W200089869 cites W2055591121 @default.
- W200089869 cites W2061512373 @default.
- W200089869 cites W2068940553 @default.
- W200089869 cites W2072050350 @default.
- W200089869 cites W2074197013 @default.
- W200089869 cites W2076648235 @default.
- W200089869 cites W2078658159 @default.
- W200089869 cites W2084310253 @default.
- W200089869 cites W2087176239 @default.
- W200089869 cites W2089777064 @default.
- W200089869 cites W2105576479 @default.
- W200089869 cites W2107422551 @default.
- W200089869 cites W2112541224 @default.
- W200089869 cites W2117031806 @default.
- W200089869 cites W2117358834 @default.
- W200089869 cites W2118236564 @default.
- W200089869 cites W2122160668 @default.
- W200089869 cites W2134266350 @default.
- W200089869 cites W2140391468 @default.
- W200089869 cites W2151700694 @default.
- W200089869 cites W2153121077 @default.
- W200089869 cites W2153988951 @default.
- W200089869 cites W2154643595 @default.
- W200089869 cites W2162604832 @default.
- W200089869 cites W2164966976 @default.
- W200089869 cites W2165860616 @default.
- W200089869 cites W2168851457 @default.
- W200089869 cites W2169042936 @default.
- W200089869 cites W2175016850 @default.
- W200089869 cites W2238597397 @default.
- W200089869 cites W2288400359 @default.
- W200089869 cites W2560497666 @default.
- W200089869 cites W2571043442 @default.
- W200089869 cites W3011736922 @default.
- W200089869 cites W3137131138 @default.
- W200089869 cites W53383054 @default.
- W200089869 cites W634726937 @default.
- W200089869 cites W972906859 @default.
- W200089869 hasPublicationYear "2002" @default.
- W200089869 type Work @default.
- W200089869 sameAs 200089869 @default.
- W200089869 citedByCount "1" @default.
- W200089869 crossrefType "journal-article" @default.
- W200089869 hasAuthorship W200089869A5081111645 @default.
- W200089869 hasConcept C118518473 @default.
- W200089869 hasConcept C120217122 @default.
- W200089869 hasConcept C127413603 @default.
- W200089869 hasConcept C166957645 @default.
- W200089869 hasConcept C205649164 @default.
- W200089869 hasConcept C39432304 @default.
- W200089869 hasConcept C41008148 @default.
- W200089869 hasConcept C54286561 @default.
- W200089869 hasConcept C88463610 @default.
- W200089869 hasConceptScore W200089869C118518473 @default.
- W200089869 hasConceptScore W200089869C120217122 @default.
- W200089869 hasConceptScore W200089869C127413603 @default.
- W200089869 hasConceptScore W200089869C166957645 @default.
- W200089869 hasConceptScore W200089869C205649164 @default.
- W200089869 hasConceptScore W200089869C39432304 @default.
- W200089869 hasConceptScore W200089869C41008148 @default.
- W200089869 hasConceptScore W200089869C54286561 @default.
- W200089869 hasConceptScore W200089869C88463610 @default.
- W200089869 hasLocation W2000898691 @default.
- W200089869 hasOpenAccess W200089869 @default.
- W200089869 hasPrimaryLocation W2000898691 @default.
- W200089869 hasRelatedWork W1563220993 @default.
- W200089869 hasRelatedWork W1863112376 @default.