Strategies to increase nitrogen use efficiency and reduce nitrate leaching in vegetable production in the Netherlands

Environmental concern and legislation of fertilization requires strategies to increase nitrogen use efficiency and reduce nitrate leaching. Strategies can be fertilizer choice, timing of N availability and fertilizer placement. Rainfall in the experimental year 2007 was moderate and different strategies were therefore not seriously tested. However, for crops that allow regular fertilization, it is questionable whether special fertilizers can do better than calcium ammonium nitrate (CAN) when fertilizers are applied according to good practice (i.e., row application, side dressing and split applications). Specific application of small amounts of N near planted endive showed increased initial growth, even at high levels of soil mineral N, and was found to lead in one of two plantings to increased yield at harvest. Substitution of broadcast N before planting by a starter application close to the plants followed by side dressing maintains maximum production while leaching risk is reduced

Feed the crop or feed the soil? A case study in leek (Allium porrum L.)

The purpose of our study was to assess the role of soil quality parameters in leek production and to assess their importance relative to nitrogen (N) applied as fertilizer. We selected seven (2004) and seven (2005) fields on leek farms in the southern sand district of the Netherlands and measured physical and chemical soil properties. Three N rates (0, 90 and 360 kg N ha-1 as calcium ammonium nitrate; denoted as N0, N90, N360) were given at each site. Leek (Allium porrum L. ‘Kenton’) was planted in June-July and harvested next spring. Measured response variables were shoot biomass yield (gross and net, fresh and dry) and shoot N-yield (gross, net) at harvest. Pooled data from both years were analyzed by linear regression. N uptake from unfertilized soil (U0), and topsoil properties soluble organic N (Nso), soil organic matter content (SOM), total nitrogen (Ntot) and water content at field capacity (Wfc) all had large and significant impacts on biomass yield and N yield. These five properties (Xi) were correlated and were therefore used alternately in regression models. Effects of soil properties found by regression refer to a shift in the regressor from its 25% to its 75% percentile value, and are expressed here relative to mean yields (both years, all treatments). This normalization facilitates direct comparison with fertilizer effects. Normalized effects of Xi variables on biomass yield and N yield were between +0.10 and +0.20. Effects of fertilizer application at N90 were about +0.10 (biomass yield) and +0.20 (N yield). At N360 effects were +0.10 to +0.20 (biomass yield) and +0.30 to +0.40 (N-yield). So while N fertilizer strongly promoted N-uptake relative to growth, soil properties Xi affected growth and N yield more evenly. With shifts in Xi variables, dry matter produced per kg additional N uptake was 1.49 to 1.77 times larger than with extra N uptake resulting from fertilizer application at N90. This indicates that soil properties Xi promoted yield not only via enhanced N supply. Besides effects of Xi properties and N fertilizer, we found significant effects of year, soil texture, pH and inorganic soil N at planting, on biomass yield. Texture parameters Fsfine (50-210 µm) and M50 (median of particle size in 50-2000 µm fraction) had large and additive positive effects on net fresh yield. Apparent recovery of fertilizer N (ANR) averaged 0.35 at N90, and 0.17 at N360. ANR decreased with higher Nso and increased with higher Wfc

The fate of nitrogen from crop residues of broccoli, leek and sugar beet

Environmental concern has lead to legislation on fertilization to reduce nutrient losses to the environment. Reducing N input may be inadequate for crops that have a high N content in their residues. Reducing N input will negatively affect yield, but the residues remain. Management of crop residues may then be a more effective strategy to reduce N losses, notably nitrate leaching. Two experiments were carried out in 2006-07 and 2007-08 to study all emission routes of N from crop residues of broccoli, leek and sugar beet, and to determine the contribution of N from the residues to nitrate in groundwater. Crop residues were surface applied or rototilled, and compared with a blank and application of fertilizer N. About 11 to 16% of the N-content was lost to the air. Total N-losses to the air as ammonia and through denitrification were little affected by tillage, but partitioning was. When residues were left on the soil surface, most N was lost as ammonia, when the residues were rototilled, most N was lost through denitrification. Year strongly affected N leaching from crop residues, and the fraction of N from crop residues that was leached was twice as high in 2006-07 than in 2007-08. Tillage increased N leaching from broccoli, but had little effect with leek or sugar beet. Between 20 and 60% of the N content of residues of leek and broccoli was leached. Removal of residues after harvest will therefore contribute to reduce N leaching. However, options for treatment and re-use of the residues need to be studied as well as the effects on nitrate leaching and gaseous losses to assess the effects of the system as a whol

Dendritic Cells and T Lymphocytes in the Pathogenesis of Pulmonary Sarcoidosis

The history of sarcoidosis begins in 1899 when the Norwegian dermatologist Ceasar Boeck described nodular skin lesions characterized by epitheloid cells and a few giant cells as multiple benign sarcoid of the skin. Now, many years later, a lot more is known about sarcoidosis. The definition of sarcoidosis is described in the American Thoracic Society statement on sarcoidosis in 1999: sarcoidosis is regarded as a multisystem disorder of unknown cause, commonly affecting young and middle aged adults, with bilateral hilar adenopathy, pulmonary infiltrates, eye and skin lesions. Also oth

Symmetry transformations for square sliced three-way arrays, with applications to their typical rank

AbstractThe typical 3-tensorial rank has been much studied over algebraically closed fields, but very little has been achieved in the way of results pertaining to the real field. The present paper examines the typical 3-tensorial rank over the real field, when the slices of the array involved are square matrices. The typical rank of 3×3×3 arrays is shown to be five. The typical rank of p×q×q arrays is shown to be larger than q+1 unless there are only two slices (p=2), or there are three slices of order 2×2 (p=3 and q=2). The key result is that when the rank is q+1, there usually exists a rank-preserving transformation of the array to one with symmetric slices

Duurzaam bodembeheer in de Nederlandse landbouw : visie en bouwstenen voor een kennisagenda

Wageningen UR (University & Research centre) en het Louis Bolk Instituut hebben in opdracht van het ministerie van Economische Zaken, Landbouw en Innovatie (EL&I), voorheen ministerie van LNV, een visie opgesteld over duurzaam bodembeheer. Ook worden bouwstenen aangedragen voor een kennisagenda. Op basis hiervan kan het beleid prioriteiten stellen voor onderzoek en kennisdoorstroming. Duurzaam bodembeheer in de landbouw draagt bij aan diverse dimensies van duurzaamheid: economie (inclusief voedselvoorziening), natuur (inclusief biodiversiteit), milieu, waterhuishouding, klimaat (adaptatie en mitigatie) en welzijn van de mens (ondernemer, consument, burger en recreant). Om het begrip duurzaam bodembeheer concreet te maken, zijn in dit rapport specifieke doelen die met het bodembeheer worden nagestreefd, geformuleerd: de bodembeheerdoelen. Sommige doelen zijn gesteld vanuit het perspectief van de ondernemer, andere hebben een bredere maatschappelijke waarde