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Wageningen, Netherlands

Reijneveld A.,BLGG AgroXpertus | Oenema O.,Wageningen University
Nutrient Cycling in Agroecosystems | Year: 2012

Compliance with current phosphorus (P) fertilization recommendations would ultimately result in a soil P status of agricultural land in the agronomical optimal range. In practice though there are large variations in soil P status among farms and fields. Our study aimed at increasing the understanding of the cause-effect relationships for these spatial variations in soil P test values. The Northeast Polder in The Netherlands was chosen as study area, because of its characteristics. It was reclaimed from the sea in 1942, has one major soil type (calcareous loam), well-educated farmers, one dominant land use (arable farming) and little pressure to use animal manure. We tested the hypothesis that in this polder mean P status has developed towards the optimal range with a small standard deviation. We analysed available soil P analyses records (>30,000) from the period ~1950-2004, and conducted a questionnaire about fertilization practices among farmers. The soil P(w) values increased steadily and significantly from the agronomical range 'low' to 'ample sufficient' from 1971 to 2004. Variation within and between farms also increased. About 45 % of the farmers appear to aim at a soil P status above the agronomical optimal range, and <70 % of the farmers indicated that they are uncertain whether the obtained increase in soil P(w) status is actually plant available P. In conclusion, our hypothesis was rejected: for farmers in our study area, risk avoidance seems the decisive factor for pursuing a soil P status above the agronomical optimal range. If even well-educated farmers question the official fertilizer recommendations and aim at higher levels of soil P fertility, also other farmers worldwide may continue to aim such supra-optimal soil P status. This is undesirable given the diminishing P resources. Possible solutions could be to define more refined P fertilization recommendations and better and more intensified communication of those recommendations to farmers and their advisers. © 2012 Springer Science+Business Media B.V. Source


Reijneveld A.,BLGG AgroXpertus | Termorshuizen A.,BLGG Research | Vedder H.,BLGG Research | Oenema O.,Wageningen University
Communications in Soil Science and Plant Analysis | Year: 2014

Soil phosphorus (P) tests are used for P fertilization recommendations, environmental evaluations, and occasionally for legislation purposes. The basis of fertilization recommendation as function of soil P status was established in the 1950s-1960s. Since then the agroeconomic environment has altered: Environmental protection became increasingly important and P rock resources for fertilizers appeared exhaustible. Also, new insights in soil testing and fertilization recommendations reflecting more efficient use of P became available. However, these new insights seem hard to implement into agricultural practice, to a large extent because replacing existing soil tests and recommendations would imply a very significant effort with respect to introducing new tests and recommendations by fertilization trials in practice. The same would apply for environmental evaluations. Here, a novel, three-step schedule for introducing new soil tests is proposed: (1) establishing new promising soil tests, (2) creating regression models between the old and new soil tests, and (3) implementing the new soil test stepwise by fertilization trials. In this way, the knowledge based on the old soil tests can be used until the new soil tests and their subsequent crop responses are validated sufficiently. As a novel P test we considered combining soil P intensity [as reflected by P-calcium chloride (CaCl2)] with P capacity [as reflected by P-ammonium lactate (Al)] and P-buffering capacity (as reflected by P-Al/P-CaCl2 ratio) characteristics. Researchers tested whether this novel soil test can predict P water (Pw), P-calcium lactate / acetate (CAL), and P-Olsen values. To test the hypothesis, four datasets were used (two with Pw, one with P-CAL, and one with P-Olsen). In all datasets additional soil characteristics were available including soil type. Regression models with Radj 2 from 0.80 to 0.93 were obtained by using P-Al, P-CaCl2, and soil type. It can be concluded that these regressions can be used as a helpful intermediate instrument when introducing fertilization recommendations based on new soil tests. Predicting one soil P test out of other soil characteristics, analogous to the predicted Pw, P-CAL, and P-Olsen, could also be helpful in comparing P statuses of agricultural land in different nations. © 2014 Taylor and Francis Group, LLC. Source


Reijneveld J.A.,BLGG AgroXpertus | Abbink G.W.,BLGG AgroXpertus | Termorshuizen A.J.,BLGG Research | Oenema O.,Wageningen University
European Journal of Agronomy | Year: 2014

It is reasonable to expect that compliance with grassland fertilization recommendations in the long run results in optimal soil fertility, and subsequent herbage quality. Here, we evaluate the development of soil, herbage and manure characteristics and their relation over the last decades. We hypothesized that herbage and manure quality are related with soil fertility. We used a large database with results of soil tests, spring forage quality characteristics, and manure analyses, which were made on demand of dairy farmers. We considered the Netherlands as a whole and three selected regions with contrasting soil types (sandy soil, riverine clay, and peaty marine clay). Effects of soil fertility on herbage quality were evident when comparing farms. Farms higher in soil P and K generally have correspondingly higher contents in forage. On average, soil fertility and herbage characteristics were within or just above the agronomical optimal range during the last decades. Herbage crude protein content decreased in all regions during last two decades, which is likely an effect of legislative measures on decreasing the application of N. Selenium (Se) and sulphur (S) contents increased sharply on sandy soils, likely because of increased use of Se and S containing fertilizers. Manure composition did not differ between soil types. In conclusion, at farm level, the element composition of herbage reflected the soil fertility status. The contents of S, P, K, Na, Mg, and Ca in the herbage were all significantly influenced by soil fertility characteristics. Our results emphasize the importance of maintaining soil fertility for high quality roughage production. © 2014 Elsevier B.V. Source


Rybarczyk-Mydlowska K.,Wageningen University | Mooyman P.,Wageningen University | Van Megen H.,Wageningen University | Van Den Elsen S.,Wageningen University | And 7 more authors.
Phytopathology | Year: 2012

Foliar nematodes, plant-parasitic representatives of the genus Aphelenchoides, constitute a minority in a group dominated by fungivorous species. Distinction between (mostly harmless) fungal feeding Aphelenchoides species and high impact plant parasites such as A. besseyi, A. fragariae, A. ritzemabosi, and A. subtenuis is severely hampered by the scarcity of informative morphological characters, some of which are only observable in specific developmental stages. Poor description of a number of non-plant-parasitic Aphelenchoides species further complicates identification. Based on (nearly) full-length small subunit ribosomal DNA (SSU rDNA) sequences (?1,700 bp), a phylogenetic tree was generated, and the four target species appeared as distinct, well-supported groups. Notably, this genus does not constitute a monophyletic group: A. besseyi and A. ritzemabosi cluster together and they are phylogenetically isolated from A. fragariae, A. subtenuis, and most other fungivorous species. A phylum-wide SSU rDNA framework was used to identify species-specific DNA motifs. For the molecular detection of four plant-parasitic Aphelenchoides species, polymerase chain reaction primers were developed with high, identical annealing temperatures (63°C). Within the molecular framework presented here, these primers can be used for the rapid screening of plant material and soil for the presence of one or multiple foliar nematode species. © 2012 The American Phytopathological Society. Source


Brus D.J.,Wageningen University | Orton T.G.,University of Sydney | Walvoort D.J.J.,Wageningen University | Reijneveld J.A.,BLGG AgroXpertus | Oenema O.,Wageningen University
Geoderma | Year: 2014

The summary statistics (SS) approach to area-to-point (ATP) kriging is applied to map organic matter concentration in the topsoil of agricultural fields from aggregated soil testing data. The differences between the SS approach and earlier published ATP kriging methods are explained and the behavior of the SS predictions is illustrated with a simulation experiment. In conventional ATP kriging, the areal means provide the data and are treated as errorless. In the SS approach, the data for each areal unit comprise the number of observations from the unit and the mean and variance of these observations; the approach deals with these data so that uncertainty in the areal means is accounted for. The SS approach is based on a point support covariance model, which is recovered from the areal data by restricted maximum likelihood. Validation using 339 georeferenced fields showed that the mean squared error (MSE) with the SS approach was slightly smaller than with the reference method that uses the postcode district (PCD) average as predictor. In PCDs with less than 25 sampled fields the reference MSE was reduced by 10%, but with more than 100 sampled fields the MSEs were about equal. Validation of the prediction variances was performed using the standardized squared prediction errors (SSEs). The SS approach slightly over-estimated the prediction error variances, although the mean and median of the SSEs were not outside the expected range of values. The reference method under-estimated the prediction error variance. © 2014 Elsevier B.V. Source

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