Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Impacts of intensifying or expanding cereal cropping in sub-Saharan Africa on greenhouse gas emissions and food security
Loon, Marloes P. van; Hijbeek, Renske ; Berge, Hein F.M. ten; Sy, Veronique De; Broeke, Guus A. ten; Solomon, Dawit ; Ittersum, Martin K. van - \ 2019
Global Change Biology 25 (2019)11. - ISSN 1354-1013 - p. 3720 - 3730.
fertilizer - food self-sufficiency - intensification - land use conversion - nitrogen - nutrient use efficiency - yield gaps

Cropping is responsible for substantial emissions of greenhouse gasses (GHGs) worldwide through the use of fertilizers and through expansion of agricultural land and associated carbon losses. Especially in sub-Saharan Africa (SSA), GHG emissions from these processes might increase steeply in coming decades, due to tripling demand for food until 2050 to match the steep population growth. This study assesses the impact of achieving cereal self-sufficiency by the year 2050 for 10 SSA countries on GHG emissions related to different scenarios of increasing cereal production, ranging from intensifying production to agricultural area expansion. We also assessed different nutrient management variants in the intensification. Our analysis revealed that irrespective of intensification or extensification, GHG emissions of the 10 countries jointly are at least 50% higher in 2050 than in 2015. Intensification will come, depending on the nutrient use efficiency achieved, with large increases in nutrient inputs and associated GHG emissions. However, matching food demand through conversion of forest and grasslands to cereal area likely results in much higher GHG emissions. Moreover, many countries lack enough suitable land for cereal expansion to match food demand. In addition, we analysed the uncertainty in our GHG estimates and found that it is caused primarily by uncertainty in the IPCC Tier 1 coefficient for direct N2O emissions, and by the agronomic nitrogen use efficiency (N-AE). In conclusion, intensification scenarios are clearly superior to expansion scenarios in terms of climate change mitigation, but only if current N-AE is increased to levels commonly achieved in, for example, the United States, and which have been demonstrated to be feasible in some locations in SSA. As such, intensifying cereal production with good agronomy and nutrient management is essential to moderate inevitable increases in GHG emissions. Sustainably increasing crop production in SSA is therefore a daunting challenge in the coming decades.

Plant trait-based approaches to improve nitrogen cycling in agroecosystems
Abalos, Diego ; Groenigen, Jan Willem van; Philippot, Laurent ; Lubbers, Ingrid M. ; Deyn, Gerlinde B. De - \ 2019
Journal of Applied Ecology 56 (2019)11. - ISSN 0021-8901 - p. 2454 - 2466.
agroecosystems - fertilizer - functional traits - nitrogen cycling - nitrogen losses - plant mixtures - plant traits - plant–soil interactions

Intensive agriculture is dominated by monocultures of high-yielding plants that receive large applications of nitrogen (N) fertilizers to boost plant productivity. However, these systems have low N use efficiency (NUE) as fertilized plants generally take up less than half of the N applied. A large fraction of the remainder N is susceptible to be lost from the agroecosystem generating a cascade of environmental and socio-economic problems. Climate change and projected global increases in fertilizer use pose further risks to N losses and yield stability. We review and translate concepts from ecology in natural systems to demonstrate that NUE in intensive agroecosystems can be strongly increased by fine-tuning the traits of the plant communities to the levels of N fertilization intensity. We present key plant traits of importance for N-cycling (architectural, morphological and physiological traits, as well as symbiotic associations and exudation patterns); discuss ecological (with soil fauna and N-cycling microbial communities) and agronomic interactions of this approach; propose interdisciplinary methodologies for future research ranging from pot to global scales; and highlight possible solutions leading to an optimal balance between N fertilizer use and productivity. Synthesis and applications. By showing the strong links between plant traits and nitrogen (N) cycling, our work opens possibilities to test ecologically informed hypotheses across gradients of soil fertility and N fertilizer management intensity, setting a research agenda for the coming years. Accordingly, the choice of plant species based on their functional traits will play a central role for the development of modern and productive agroecosystems that retain and use N more efficiently.

Recycling nutrients contained in human excreta to agriculture: Pathways, processes, and products
Harder, Robin ; Wielemaker, Rosanne ; Larsen, Tove A. ; Zeeman, Grietje ; Öberg, Gunilla - \ 2019
Critical Reviews in Environmental Science and Technology 49 (2019)8. - ISSN 1064-3389 - p. 695 - 743.
blackwater - carbon - feces - fertilizer - nitrogen - organic matter - Phosphorus - potassium - recovery - resource-oriented sanitation - sewage - soil amendment - source-separation - urine - wastewater

The need for better nutrient management has spurred efforts towards more comprehensive recycling of nutrients contained in human excreta to agriculture. Research in this direction has intensified throughout the past years, continuously unfolding new knowledge and technologies. The present review aspires to provide a systematic synthesis of the field by providing an accessible overview of terminology, recovery pathways and treatment options, and products rendered by treatment. Our synthesis suggests that, rather than focusing on a specific recovery pathway or product and on a limited set of nutrients, there is scope for exploring how to maximize nutrient recovery by combining individual pathways and products and including a broader range of nutrients. To this end, finding ways to more effectively share and consolidate knowledge and information on recovery pathways and products would be beneficial. The present review aims to provide a template that aims to facilitate designing human excreta management for maximum nutrient recovery, and that can serve as foundation for organizing and categorizing information for more effective sharing and consolidation.

Effects of Nutrient Antagonism and Synergism on Yield and Fertilizer Use Efficiency
Rietra, René P.J.J. ; Heinen, Marius ; Dimkpa, Chistian O. ; Bindraban, Prem S. - \ 2017
Communications in Soil Science and Plant Analysis 48 (2017)16. - ISSN 0010-3624 - p. 1895 - 1920.
Antagonism - fertilizer - macronutrients - micronutrients - synergism

Interaction among plant nutrients can yield antagonistic or synergistic outcomes that influence nutrient use efficiency. To provide insight on this phenomenon, peer-reviewed articles were selected that quantified the interaction effects of nutrients on crop yield levels. In total 94 articles were selected that described 117 interactions between all macro- and micronutrients for different agricultural crops. In 43 cases the interaction was synergistic, in 17 cases the interaction was antagonistic, and in 35 cases the interaction was zero-interaction; the other 23 cases were non-significant (16) or showed a negative response (7). Generally: (a) when the availability of two nutrients is characterized as deficient, a large increase in yield can be expected by diminishing these deficiencies: (b) for most macronutrients the mutual interactions on yield levels are synergistic; and (c) antagonistic effects on yield are often found for divalent cations. Knowledge of nutrient interactions can guide fertilizer design and optimization of fertilization strategies for high yields and high nutrient use efficiencies.

Economic performance and sustainability of a novel intercropping system on the north China plain
Huang, C. ; Liu, Q. ; Heerink, N.B.M. ; Stomph, T.J. ; Li, B. ; Liu, R. ; Zhang, H. ; Wang, C. ; Li, X. ; Zhang, C. ; Werf, W. van der; Zhang, F. - \ 2015
PLoS ONE 10 (2015)8. - ISSN 1932-6203 - 16 p.
reducing environmental risk - nutrient-use efficiency - food security - crop productivity - n management - resource use - agriculture - competition - fertilizer - diversity
Double cropping of wheat and maize is common on the North China Plain, but it provides limited income to rural households due to the small farm sizes in the region. Local farmers in Quzhou County have therefore innovated their production system by integration of watermelon as a companion cash crop into the system. We examine the economic performance and sustainability of this novel intercropping system using crop yield data from 2010 to 2012 and farm household survey data collected in 2012. Our results show that the gross margin of the intercropping system exceeded that of the double cropping system by more than 50% in 2012. Labor use in the intercropping system was more than three times that in double cropping. The lower returns per labor hour in intercropping, however, exceeded the average off-farm wage in the region by a significant margin. Nutrient surpluses and irrigation water use are significant larger under the intercropping system. We conclude that the novel wheat-maize/watermelon intercropping system contributes to rural poverty alleviation and household-level food security, by raising farm incomes and generating more employment, but needs further improvement to enhance its sustainability.
Nitrous oxide and methane emissions from optimized and alternative cereal cropping systems on the North China Plain: A two-year field study
Gao, B. ; Ju, X.T. ; Su, F. ; Meng, Q.F. ; Oenema, O. ; Christie, P. ; Chen, X.P. ; Zhang, F.S. - \ 2014
Science of the Total Environment 472 (2014). - ISSN 0048-9697 - p. 112 - 124.
greenhouse-gas emissions - n2o emissions - soil - management - maize - fertilizer - fluxes - agriculture - balance - intensity
The impacts of different crop rotation systems with their corresponding management practices on grain yield, greenhouse gas emissions, and fertilizer nitrogen (N) and irrigation water use efficiencies are not well documented. This holds especially for the North China Plain which provides the staple food for hundreds of millions of people and where groundwater resources are polluted with nitrate and depleted through irrigation. Here, we report on fertilizer N and irrigation water use, grain yields, and nitrous oxide (N2O) and methane (CH4) emissions of conventional and optimized winter wheat-summer maize double-cropping systems, and of three alternative cropping systems, namely a winter wheat-summer maize (or soybean)-spring maize system, with three harvests in two years; and a single spring maize system with one crop per year. The results of this two-year study show that the optimized double-cropping system led to a significant increase in grain yields and a significant decrease in fertilizer N use and net greenhouse gas intensity, but the net greenhouse gas N2O emissions plus CH4 uptake and the use of irrigation water did not decrease relative to the conventional system. Compared to the conventional system the net greenhouse gas emissions, net greenhouse gas intensity and use of fertilizer N and irrigation water decreased in the three alternative cropping systems, but at the cost of grain yields except in the winter wheat-summer maize-spring maize system. Net uptake of CH4 by the soil was little affected by cropping system. Average N2O emission factors were only 0.17% for winter wheat and 0.53% for maize. In conclusion, the winter wheat-summer maize-spring maize system has considerable potential to decrease water and N use and decrease N2O emissions while maintaining high grain yields and sustainable use of groundwater.
Soil biochar amendment in a nature restoration area: effects on plant productivity and community composition
Voorde, T.F.J. van de; Bezemer, T.M. ; Groenigen, J.W. van; Jeffery, S.L. ; Mommer, L. - \ 2014
Ecological Applications 24 (2014)5. - ISSN 1051-0761 - p. 1167 - 1177.
nitrogen-fixation - activated carbon - charcoal - invasion - growth - performance - fertilizer - amazon - manure
Biochar (pyrolyzed biomass) amendment to soils has been shown to have a multitude of positive effects, e.g., on crop yield, soil quality, nutrient cycling, and carbon sequestration. So far the majority of studies have focused on agricultural systems, typically with relatively low species diversity and annual cropping schemes. How biochar amendment affects plant communities in more complex and diverse ecosystems that can evolve over time is largely unknown. We investigated such effects in a field experiment at a Dutch nature restoration area. In April 2011, we set up an experiment using biochar produced from cuttings collected from a local natural grassland. The material was pyrolyzed at 400°C or at 600°C. After biochar or residue (non-pyrolyzed cuttings) application (10 Mg/ha), all plots, including control (0 Mg/ha) plots, were sown with an 18-species grassland mixture. In August 2011, we determined characteristics of the developed plant community, as well as soil nutrient status. Biochar amendment did not alter total plant productivity, but it had a strong and significant effect on plant community composition. Legumes were three times as abundant and individual legume plants increased four times in biomass in plots that received biochar as compared to the control treatment. Biomass of the most abundant forb (Plantago lanceolata) was not affected by biochar addition. Available phosphorous, potassium, and pH were significantly higher in soils that received biochar than in Control soils. The rate of biological nitrogen fixation and seed germination were not altered by biochar amendment, but the total amount of biological N fixed per Trifolium pratense (red clover) plant was more than four times greater in biochar-amended soil. This study demonstrates that biochar amendment has a strong and rapid effect on plant communities and soil nutrients. Over time these changes may cascade up to other trophic groups, including above- and belowground organisms. Our results emphasize the need for long-term studies that examine not only the short-term effects of biochar amendment, but also follow how these effects evolve over time and affect ecosystem functioning.
Key role of China and its agriculture in global sustainable phosphorus management
Sattari, S.Z. ; Ittersum, M.K. van; Giller, K.E. ; Zhang, F. ; Bouwman, A.F. - \ 2014
Environmental Research Letters 9 (2014)5. - ISSN 1748-9326 - 8 p.
environmental impacts - soil-phosphorus - crop yield - food-chain - fertilizer - nitrogen - perspective - scarcity - balances - industry
Growing global demand for food leads to increased pressure on phosphorus (P), a finite and dwindling resource. China is the largest producer and consumer of P fertilizer in the world. A mass balance analysis of historical P use on China's arable land shows that P input substantially exceeds crop P uptake leading to the accumulation of residual soil P. A Dynamic P Pool Simulator (DPPS) model is applied to estimate future P demand in China's arable land. Our simulations show that more sustainable use of P accounting for the residual P can save ca. 20% of the P fertilizer needed until 2050 in China relative to the Rio + 20 Trend scenario. This saving would be equivalent to half of the P required in Africa or sufficient for Western Europe to achieve target crop P uptake in 2050.
Behavioral Responses and the Impact of New Agricultural Technologies: Evidence from a Double-blind Field Experiment in Tanzania
Bulte, E.H. ; Beekman, G. ; Falco, S. Di; Hella, J.P. ; Pan, L. - \ 2014
American Journal of Agricultural Economics 96 (2014)3. - ISSN 0002-9092 - p. 813 - 830.
adoption - kenya - farmers - revolution - fertilizer - decisions - economics - trials - model
Randomized controlled trials (RCTs) in the social sciences are typically not double-blind, so participants know they are “treated” and will adjust their behavior accordingly. Such effort responses complicate the assessment of impact. To gauge the potential magnitude of effort responses we implement a conventional RCT and double-blind trial in rural Tanzania, and randomly allocate modern and traditional cowpea seed varieties to a sample of farmers. Effort responses can be quantitatively important—for our case they explain the entire “treatment effect on the treated” as measured in a conventional economic RCT. Specifically, harvests are the same for people who know they received the modern seeds and for people who did not know what type of seeds they got; however, people who knew they had received the traditional seeds did much worse. Importantly, we also find that most of the behavioral response is unobserved by the analyst, or at least not readily captured using coarse, standard controls.
Liebig's law of the minimum applied to a greenhouse gas: Alleviation of P-limitation reduces soil N2O emmission
Baral, B.R. ; Kuyper, T.W. ; Groenigen, J.W. van - \ 2014
Plant and Soil 374 (2014)1-2. - ISSN 0032-079X - p. 539 - 548.
nitrous-oxide emission - agricultural soils - phosphorus - fertilizer - denitrification - mineralization - mycorrhizas - netherlands - grassland - release
Emission of the greenhouse gas (GHG) nitrous oxide (N2O) are strongly affected by nitrogen (N) fertilizer application rates. However, the role of other nutrients through stoichiometric relations with N has hardly been studied. We tested whether phosphorus (P) availability affects N2O emission. We hypothesized that alleviation of plant P-limitation reduces N2O emission through lowering soil mineral N concentrations. We tested our hypothesis in a pot experiment with maize (Zea mays L.) growing on a P-limiting soil/sand mixture. Treatment factors included P and N fertilization and inoculation with Arbuscular Mycorrhizal Fungi (AMF; which can increase P uptake). Both N and P fertilization, as well as their interaction significantly (P <0.01) affected N2O emission. Highest N2O emissions (2.38 kg N2O-N ha(-1)) were measured at highest N application rates without P fertilization or AMF. At the highest N application rate, N2O fluxes were lowest (0.71 kg N2O-N ha(-1)) with both P fertilization and AMF. The N2O emission factors decreased with 50 % when P fertilization was applied. Our results illustrate the importance of the judicious use of all nutrients to minimize N2O emission, and thereby further underline the intimate link between sound agronomic practice and prudent soil GHG management.
East African highland bananas (Musa spp. AAA-EA) 'worry' more about potassium deficiency than drought stress
Taulya, G. - \ 2013
Field Crops Research 151 (2013). - ISSN 0378-4290 - p. 45 - 55.
foliar nutrient status - biomass allocation - osmotic adjustment - plant-growth - root ratio - soil-water - nitrogen - shoot - fertilizer - weevil
Drought stress, potassium (K) and nitrogen (N) deficiencies are major constraints to rain-fed East African highland banana (EAHB) production in Uganda. It was hypothesised that the reduction in fresh bunch mass and increase in dry matter (DM) allocation to corms with drought stress, K and N deficiency is additive. Individual plant measurements at harvest from two field trials in central and south western Uganda were analyzed to evaluate effects of cumulative rainfall (CRF) received 365 days from sucker emergence, mineral K and N inputs on EAHB bunch yields. Dry matter content in aerial shoot (leaves and pseudostems) relative to that in the subterranean corm was also analyzed to evaluate DM allocation plasticity due to drought stress, K and N deficiency. This was verified with allometric analysis using pre-harvest stage plants from farms of known K and N nutritional status and plants from a screen house drought stress pot trial in Uganda. Dry matter production and yields were mainly driven by K interacting with CRF. Within 12 months, K input (250-600 kg K ha(-1) yr(-1)) increased bunch yield from 8 to 15 Mg ha(-1) yr(-1) irrespective of whether dry (CRF <1100 mm) or wet (CRF >= 1100 mm) conditions prevailed, possibly due to K-mediated osmotic adjustment under dry conditions. Without K input, wet conditions increased bunch yield from 6 to 8 Mg ha(-1) yr(-1) while dry conditions decreased it from 6 to 4 Mg ha(-1) yr(-1) within 12 months. Total DM and its distribution between the biomass structures followed similar trends. Nitrogen input (150-400 kg N ha(-1) yr(-1)) neither affected bunch yield nor DM allocation at harvest stage. At pre-harvest stage, reduction in DM allocation to the corm per unit increase in total DM was 14-22% significantly lower with N and/or K deficiency compared with that under sufficient K and N. Drought stress per se had no effect on DM allocation but enhanced DM allocation shifts due to K deficiency. Drought-stressed EAHB thus increase DM allocation to subterranean structures only if K-deficient, unlike responses reported for other plant species. Potassium nutrition is perhaps a more viable entry point for mitigation of drought stress in EAHB cropping systems than irrigation but this requires further agronomic and economic evaluation. It may be important to account for carbon allocated to osmotic adjustment for realistic simulation of water- and K-limited growth in EAHB. (c) 2013 Elsevier B.V. All rights reserved.
Water and nutrient transport on a heavy clay soil in a fluvial plain in the Netherlands
Salm, C. van der; Toorn, A. van den; Chardon, W.J. ; Koopmans, G.F. - \ 2012
Journal of Environmental Quality 41 (2012)1. - ISSN 0047-2425 - p. 229 - 241.
surface runoff - phosphorus losses - subsurface drainage - grassland soil - organic phosphorus - agricultural land - nitrogen - fertilizer - bioavailability - management
In flat areas, transport of dissolved nutrients by water through the soil matrix to groundwater and drains is assumed to be the dominant pathway for nutrient losses to ground- and surface waters. However, long-term data on the losses of nutrients to surface water and the contribution of various pathways is limited. We studied nutrient losses and pathways on a heavy clay soil in a fluvial plain in The Netherlands during a 5-yr period. Average annual nitrogen (N) and phosphorus (P) losses to surface water were 15.1 and 3.0 kg ha-1 yr-1, respectively. Losses were dominated by particulate N (50%) and P (70%) forms. Rapid discharge through trenches was the dominant pathway (60–90%) for water and nutrient transport. The contribution of pipe drains to the total discharge of water and nutrients was strongly related to the length of the dry period in the preceding summer. This relationship can be explained by the very low conductivity of the soil matrix and the formation of shrinkage cracks during summer. Losses of dissolved reactive P through pipe drains appear to be dominated by preferential flow based on the low dissolved reactive P concentration in the soil matrix at this depth. Rainfall occurring after manure application played an important role with respect to the annual losses of N and P in spring when heavy rainfall occurred within 2 wk after manure application.
Social Capital and Agricultural Innovation in Sub Saharan Africa
Rijn, F.C. van; Bulte, E.H. ; Adekunle, A. - \ 2012
Agricultural Systems 108 (2012). - ISSN 0308-521X - p. 112 - 122.
rural tanzania - networks - adoption - trust - fertilizer - economics - models
In this paper we use a novel and extensive dataset to explore the association between different forms of social capital and innovation in agriculture, for a sample of African countries. We find mixed evidence. While structural social capital, especially in the form of connections beyond the village, is associated with more extensive adoption of innovations, the reverse is true for cognitive social capital (capturing shared norms and trust within the local community).
The biodegradability of EDDHA chelates under calcareous soil conditions
Schenkeveld, W.D.C. ; Hoffland, E. ; Reichwein, A.M. ; Temminghoff, E.J.M. ; Riemsdijk, W.H. van - \ 2012
Geoderma 173-174 (2012). - ISSN 0016-7061 - p. 282 - 288.
enhanced phytoremediation - organic-carbon - iron chlorosis - heavy-metals - plants - phytoextraction - temperature - components - fertilizer - behavior
FeEDDHA (iron (3 +) ethylenediamine-N,N'-bis(hydroxy phenyl acetic acid) products are commonly applied to mend or prevent Fe chlorosis in plants. In soil application, racemic and meso o,o-FeEDDHA are the effective components, while o,p-FeEDDHA tends to adsorb or react to o,p-CuEDDHA. Upon interaction with soil, a plant-independent, gradual decline in soil solution concentration of meso o,o-FeEDDHA and o,p-CuEDDHA has been observed. The aim of this study was to examine to what extent biodegradation contributes to this gradual decline. A 4-week incubation experiment was done with calcareous soil to which FeEDDHA was added. The experiment involved three sterility regimes, two conditioning regimes and three time steps. Soil solution concentrations of meso o,o-FeEDDHA and o,p-CuEDDHA gradually declined in all sterility regimes. Biodegradation did not significantly contribute to the decline in concentration of any EDDHA chelate, except for CoEDDHA, which was formed in small quantities as a result of cation displacement. The rate of the process causing the decline in meso o,o-FeEDDHA and o,p-CuEDDHA concentration was higher at higher temperature and in soil not exposed to gamma irradiation. This study offers no evidence that the effectiveness of soil-applied FeEDDHA fertilizers is compromised by biodegradation
Current and future nitrous oxide emissions from African agriculture
Hickman, J.E. ; Havlikova, M. ; Kroeze, C. ; Palm, C.A. - \ 2011
Current Opinion in Environmental Sustainability 3 (2011)5. - ISSN 1877-3435 - p. 370 - 378.
crop-livestock systems - nitric-oxide - millennium villages - natural savanna - soil emissions - burkina-faso - n2o - kenya - fertilizer - database
Most emission estimates of the greenhouse gas nitrous oxide (N2O) from African agriculture at a continental scale are based on emission factors, such as those developed by the IPCC Guidelines. Here we present estimates from Africa from the EDGAR database, which is derived from the IPCC emission factors. Resulting estimates indicate that N2O emissions from agriculture represented 42% of total emissions from Africa (though that rises to 71% if all savannah and grassland burning is included), or roughly 6% of global anthropogenic N2O emissions (or 11% including burning). Emissions from African agriculture are dominated by grazing livestock; 74% of agricultural N2O excluding biomass burning was from paddocks, ranges, and pasture. Direct soil emissions represent 15% of agricultural emissions; substantial changes in direct emissions from North Africa helped drive a 47% continental increase in direct soil emissions from 1970 to 2005. Future trends based on the Millennium Ecosystem Assessment scenarios indicate that agricultural N2O emissions may double in Africa by 2050 from 2000 levels. Any regional or continental estimates for Africa are, however, necessarily limited by a paucity of direct measurements of emissions in sub-Saharan agro-ecosystems, and the heavy reliance on emission factors and other default assumptions about nitrogen cycling in African agriculture. In particular, a better understanding of livestock-related N inputs and N2O emissions will help improve regional and continental estimates. As fertilizer use increases in sub-Saharan Africa, emission estimates should consider several unusual elements of African agriculture: farmer practices that differ fundamentally from that of large scale farms, the long history of N depletion from agricultural soils, seasonal emission pulses, and emission factors that vary with the amount of N added.
Lignin based controlled release coatings
Mulder, W.J. ; Gosselink, R.J.A. ; Vingerhoeds, M.H. ; Harmsen, P.F.H. ; Eastham, D. - \ 2011
Industrial Crops and Products 34 (2011)1. - ISSN 0926-6690 - p. 915 - 920.
slow-release - kraft lignin - fertilizer - formulations - urea - polymers - sorghum
Urea is a commonly used fertilizer. Due to its high water-solubility, misuse easily leads to excess nitrogen levels in the soil. The aim of this research was to develop an economically feasible and biodegradable slow-release coating for urea. For this purpose, lignin was selected as coating material. From four commercially available lignins, two lignosulfonates (Wafex P and Borresperce), a softwood kraft (Indulin AT) and soda flax lignin (Bioplast), the latter showed the best potential with respect to film forming properties. Bioplast dispersions up to a dry matter content of 50% are processable. However, high losses during processing resulted in thin coating layers on the urea granules. To reduce urea release, hydrophobic compounds and crosslinkers were added to the Bioplast dispersions. Addition of alkenyl succinic anhydride (ASA) significantly decreased the release of urea in water. However, complete release of urea still occurred within one hour, which can be explained by a low reactivity of the selected compounds towards lignin, too low percentages of applied coating or negative effects of the selected compounds on the film forming process. In addition, urea partly dissolves in the aqueous lignin dispersions due to its high water-solubility. This causes incorporation of urea in the lignin layer, which results in coatings with a low water resistance. This was improved by application of an inner coating layer with high dry matter content. In conclusion, lignin shows high potential as coating material. For industrial application, more insight in the film forming properties is desired.
Dryland maize yields and water use efficiency in response to tillage/crop stubble and nutrient management practices in China
Wang, X.B. ; Dai, K. ; Zhang, D. ; Zhang, X. ; Wang, Y. ; Zhao, Q. ; Cai, D.X. ; Hoogmoed, W.B. ; Oenema, O. - \ 2011
Field Crops Research 120 (2011)1. - ISSN 0378-4290 - p. 47 - 57.
reduced tillage - northern china - conservation tillage - nitrogen losses - prone savannas - crop residue - soil - fertilizer - agriculture - systems
Rainfed crop production in northern China is constrained by low and variable rainfall. This study explored the effects of tillage/crop residue and nutrient management practices on maize (Zea mays L.) yield, water use efficiency (WUE), and N agronomic use efficiency (NAE) at Shouyang Dryland Farming Experimental Station in northern China during 2003–2008. The experiment was set-up using a split-plot design with 3 tillage/crop residue methods as main treatments: conventional, reduced (till with crop residue incorporated in fall but no-till in spring), and no-till (with crop residue mulching in fall). Sub-treatments were 3 NP fertilizer rates: 105–46, 179–78 and 210–92 kg N and P ha-1. Maize grain yields were greatly influenced by the growing season rainfall and soil water contents at sowing. Mean grain yields over the 6-year period in response to tillage/crop residue treatments were 5604, 5347 and 5185 kg ha-1, under reduced, no-till and conventional tillage, respectively. Grain yields under no-till, were generally higher (+19%) in dry years but lower (-7%) in wet years. Mean WUE was 13.7, 13.6 and 12.6 kg ha-1 mm-1 under reduced, no-till, and conventional tillage, respectively. The no-till treatment had 8–12% more water in the soil profiles than the conventional and reduced tillage treatments at sowing and harvest time. Grain yields, WUE and NAE were highest with the lowest NP fertilizer application rates (at 105 kg N and 46 kg P ha-1) under reduced tillage, while yields and WUE tended to be higher with additional NP fertilizer rates under conventional tillage, however, there was no significant yield increase above the optimum fertilizer rate. In conclusion, maize grain yields, WUE and NAE were highest under reduced tillage at modest NP fertilizer application rates of 105 kg N and 46 kg P ha-1. No-till increased soil water storage by 8–12% and improved WUE compared to conventional tillage, thus showing potentials for drought mitigation and economic use of fertilizers in drought-prone rainfed conditions in northern China.
Method and timing of grassland renovation affects herbage yield, nitrate leaching, and nitrous oxide emission in intensively managed grasslands
Velthof, G.L. ; Hoving, I.E. ; Dolfing, J. ; Smit, A. ; Kuikman, P.J. ; Oenema, O. - \ 2010
Nutrient Cycling in Agroecosystems 86 (2010)3. - ISSN 1385-1314 - p. 401 - 412.
organic nitrogen - soil - mineralization - netherlands - clover - cultivation - fertilizer - pasture - swards
Managed grasslands are occasionally ploughed up and reseeded in order to maintain or increase the sward productivity. It has been reported that this renovation of grassland is associated with a flush of soil organic nitrogen (N) mineralization and with a temporary increase in soil mineral N contents. Here, we report on the effects of method and time of grassland renovation on herbage yield, nitrate (NO3 -) leaching and nitrous oxide (N2O) emission. Field experiments were carried out at three sites (two sandy soils and a clay soil) in the Netherlands for three years. Renovation of grassland increased the percentage of Perennial ryegrass from 48–70% up to more than 90%. However, averaged over three years, dry matter yields were higher for the reference (not reseeded) swards (on average 13.6 Mg ha-1 for the highest N application rate) than for the renovated grasslands (12.2–13.1 Mg ha-1 dry matter). Grassland renovation in April did not increase N leaching in comparison to the reference. However, renovation in September increased the risk of leaching, because mineral N contents in the 0–90 cm were in November on average 46–77 kg N ha-1 higher than in the reference. Contents of dissolved organic N (DON) in the soil were not affected by renovation. Renovation increased N2O emissions by a factor of 1.8–3.0 relative to the reference grassland. Emissions of N2O were on average higher after renovation in April (8.2 kg N2O-N ha-1) than in September (5.8 kg N2O-N ha-1). Renovation without ploughing (i.e. only chemically destruction of the sward) resulted in a lower percentage of perennial ryegrass (60–84%) than with ploughing (>90%). Moreover, N2O emissions were higher after renovation without ploughing than with ploughing. Clearly, farmers need better recommendations and tools for determining when grassland renovation has beneficial agronomic effects. Losses of N via leaching and N2O emission after renovation can probably not be avoided, but renovation in spring in stead of autumn in combination with ploughing and proper timing of fertilizer application can minimize N losses.
Phytoextraction of phosphorus-enriched grassland soils
Salm, C. van der; Chardon, W.J. ; Koopmans, G.F. ; Middelkoop, J.C. van; Ehlert, P.A.I. - \ 2009
Journal of Environmental Quality 38 (2009). - ISSN 0047-2425 - p. 751 - 761.
plant-available phosphorus - iron hydroxide - sandy soil - phosphate - fertilizer - accumulation - netherlands - extraction - capacity - dynamics
Received for publication February 7, 2008. High soil P contents in agricultural soils in the Netherlands cause excessive losses of P to surface waters. The reductions in P application rates in the present manure policy are not sufficient to reach surface water quality standards resulting from the European Water Framework Directive in 2015. Accordingly, additional measures are necessary to reduce P loading to surface water. Greenhouse experiments showed that a rapid reduction in soluble P and readily available soil P can be obtained by zero P application. However, field data confirming these findings are scarce. In 2002 a phytoextraction experiment started on four grasslands sites on sand, peat, and clay soils. The phytoextraction (mining) plots receive no P and 300 kg N ha–1 yr–1 and the grass is removed by mowing. The experiment showed that zero P application, over a period of 5 yr, led to a strong (30–90%) reduction in P concentrations in soil solution in the upper soil layer (0–0.05 m). The reduction in concentrations declined with depth. Mining also resulted in a decline in P pools in the soil solid phase. The largest decline (10–60%) was found in weakly bound P pools (water extractable P; Pw, and ammonium lactate extractable P; P-AL), whereas reductions in more strongly bound P forms were relatively small. It may be concluded that phytoextraction appears an effective method of reducing soil P concentrations in the uppermost soil layers in a couple of years and prolonged mining may thus be effective in reducing leaching and runoff of P
Allometric growth relationships of East Africa highland bananas (Musa AAA-EAHB) cv. Kisansa and Mbwazirume
Nyombi, K. ; Asten, P.J.A. van; Leffelaar, P.A. ; Corbeels, M. ; Kaizzi, C.K. ; Giller, K.E. - \ 2009
Annals of Applied Biology 155 (2009)3. - ISSN 0003-4746 - p. 403 - 418.
leaf-area estimation - biomass accumulation - radiation - crop - light - interception - morphology - fertilizer - diameter - height
Highland bananas are an important staple food in East Africa, but there is little information on their physiology and growth patterns. This makes it difficult to identify opportunities for yield improvement. We studied allometric relationships by evaluating different phenological stages of highland banana growth for use in growth assessment, understanding banana crop physiology and yield prediction. Pared corms of uniform size (cv. Kisansa) were planted in a pest-free field in Kawanda (central Uganda), supplied with fertilizers and irrigated during dry periods. In addition, tissue-cultured plants (cv. Kisansa) were planted in an adjacent field and in Ntungamo (southwest Uganda), with various nutrient addition treatments (of N, P, K, Mg, S, Zn, B and Mo). Plant height, girth at base, number of functional leaves and phenological stages were monitored monthly. Destructive sampling allowed derivation of allometric relationships to describe leaf area and biomass distribution in plants throughout the growth cycle. Individual leaf area was estimated as LA (m2) = length (m) × maximum lamina width (m) × 0.68. Total plant leaf area (TLA) was estimated as the product of the measured middle leaf area (MLA) and the number of functional leaves. MLA was estimated as MLA (m2) = -0.404 + 0.381 height (m) + 0.411 girth (m). A light extinction coefficient (k = 0.7) was estimated from photosynthetically active radiation measurements in a 1.0 m grid over the entire day. The dominant dry matter (DM) sinks changed from leaves at 1118 °C days (47% of DM) and 1518 °C days (46% of DM), to the stem at 2125 °C days (43% of DM) and 3383 °C days (58% of DM), and finally to the bunch at harvest (4326 °C days) with 53% of DM. The allometric relationship between above-ground biomass (AGB in kg DM) and girth (cm) during the vegetative phase followed a power function, AGB = 0.0001 (girth)2.35 (R2 = 0.99), but followed exponential functions at flowering, AGB = 0.325 e0.036(girth) (R2 = 0.79) and at harvest, AGB = 0.069 e0.068(girth) (R2 = 0.96). Girth at flowering was a good parameter for predicting yields with R2 = 0.7 (cv. Mbwazirume) and R2 = 0.57 (cv. Kisansa) obtained between actual and predicted bunch weights. This article shows that allometric relationship can be derived and used to assess biomass production and for developing banana growth models, which can help breeders and agronomists to further exploit the crop's potential
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