Jacob Verloop

Dr. Jacob Verloop

Wageningen University & Research, Wageningen, The Netherlands
orcid

Research Focus & Metrics

Academic Career Length

21Years (2006-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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22 April 2020 in Water
Verified
Journal Article
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SKSusanne Klages
Susanne Klages
CHClaudia Heidecke
Claudia Heidecke
BOBernhard Osterburg
Bernhard Osterburg
JBJohn Bailey
John Bailey
ICIrina Calciu
Irina Calciu
GVGerard Velthof
Gerard Velthof
Pollution of ground-and surface waters with nitrates from agricultural sources poses a risk to drinking water quality and has negative impacts on the environment. At the national scale, the gross nitrogen budget (GNB) is accepted as an indicator of pollution caused by nitrates. There is, however, little common EU-wide knowledge on the budget application and its comparability at the farm level for the detection of ground-and surface water pollution caused by nitrates and the monitoring of mitigation measures. Therefore, a survey was carried out among experts of various European countries in order to assess the practice and application of fertilization planning and nitrogen budgeting at the farm level and the differences between countries within Europe. While fertilization planning is practiced in all of the fourteen countries analyzed in this paper, according to current legislation, nitrogen budgets have to be calculated only in Switzerland, Germany and Romania. The survey revealed that methods of fertilization planning and nitrogen budgeting at the farm level are not unified throughout Europe. In most of the cases where budgets are used regularly (Germany, Romania, Switzerland), standard values for the chemical composition of feed, organic fertilizers, animal and plant products are used. The example of the Dutch Annual Nutrient Cycling Assessment (ANCA) tool (and partly of the Suisse Balance) shows that it is only by using farm-specific “real” data that budgeting can be successfully applied to optimize nutrient flows and increase N efficiencies at the farm level. However, this approach is more elaborate and requires centralized data processing under consideration of data protection concerns. This paper concludes that there is no unified indicator for nutrient management and water quality at the farm level. A comparison of regionally calculated nitrogen budgets across European countries needs to be interpreted carefully, as methods as well as data and emission factors vary across countries. For the implementation of EU nitrogen-related policies—notably, the Nitrates Directive—nutrient budgeting is currently ruled out as an entry point for legal requirements. In contrast, nutrient budgets are highlighted as an environment indicator by the OECD and EU institutions.

1 January 2006 in Nutrient Cycling in Agroecosystems
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JVJacob Verloop
Jacob Verloop
LBL. J. M. Boumans
L. J. M. Boumans
HKH. van Keulen
H. van Keulen
JOJ. Oenema
J. Oenema
GHG. J. Hilhorst
G. J. Hilhorst
LSL. B. J. Sebek
L. B. J. Sebek

12 January 2010 in Nutrient Cycling in Agroecosystems
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Journal Article
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JVJacob Verloop
Jacob Verloop
JOJ. Oenema
J. Oenema
SBS. L. G. Burgers
S. L. G. Burgers
HAH. F. M. Aarts
H. F. M. Aarts
HKH. van Keulen
H. van Keulen
In the coming decade, European dairy farms are obliged to realize a balance between phosphor (P) inputs to their farmland (in inorganic fertilizers and manure) and outputs (in crop products), the so-called P-equilibrium fertilization. The objective of the present study is to analyze the long-term effects of P-equilibrium fertilization on soil-P status (total soil-P and available soil-P), crop yield and P leaching on dry sandy soil, using data from experimental dairy farm ‘De Marke’, where P-equilibrium fertilization has been applied since 1989. For grassland, P availability is expressed in P-Al and for arable land in Pw. Total and available P status were monitored in the upper topsoil (layer 0–0.2 m). Total soil-P was also monitored in the lower topsoil (layer 0.2–0.4 m) and in the subsoil (0.4–0.6 m). From 1989 to 2006, Pw and P-Al (means of all farmland) decreased by 26 and 25%, respectively. In the same period, mean total-P content of the farmland decreased by 16%. There was a large variation in initial P status (1989) of the various plots. The rate of decline in all soil-P indicators was positively correlated to their initial values. In plots with the lowest initial values, P status did not change, while in plots with high initial values it tended to stabilize at lower levels. At equilibrium-P fertilization, Pw is estimated to stabilize at 20. This is lower than the recommended P status of Dutch soils used for maize cropping. P-Al is estimated to stabilize at 30–40, which corresponds to the current recommendations for grassland. The data show that at P-equilibrium fertilization, soil available-P status is higher in a maize-ley rotation than in permanent grassland. The decline in total P and available P did not affect crop yield, nor did it affect the P concentration in groundwater, but at ‘De Marke’, P emission to groundwater is generally low. The results obtained suggest that P-equilibrium fertilization can be compatible with efficient crop production.

9 March 2014 in Nutrient Cycling in Agroecosystems
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Journal Article
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JVJacob Verloop
Jacob Verloop
GHG. J. Hilhorst
G. J. Hilhorst
JOJ. Oenema
J. Oenema
HKH. Van Keulen
H. Van Keulen
LSL. B. J. Sebek
L. B. J. Sebek
MIMartin van Ittersum
Martin van Ittersum

1 January 2021
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Report
Closed access
JSJ.J. Schröder
J.J. Schröder
GHG.J. Hilhorst
G.J. Hilhorst
JOJ. Oenema
J. Oenema
JVJacob Verloop
Jacob Verloop
WBWim van Den Berg
Wim van Den Berg

1 January 2015 in Geoderma
Verified
Journal Article
Closed access
JVJacob Verloop
Jacob Verloop
GHG.J. Hilhorst
G.J. Hilhorst
APA.A. Pronk
A.A. Pronk
LŠL.B. Šebek
L.B. Šebek
HKH. van Keulen
H. van Keulen
MIMartin van Ittersum
Martin van Ittersum