164 research outputs found
New Challenges in Underprivileged Regions Call for People-Centered Research for Development
The need for enhancing food production and availability in underprivileged regions of the world requires the attention of scientists. This article explores the possibilities for rethinking agricultural research for development (R4D) in the light of new challenges characterized by a high degree of scientific uncertainty along with associated intense political differences of interest. New challenges that particularly influence food production in underprivileged regions include global climate change, globalization of food chains, and emerging low-carbon energy systems. We argue that by applying the people-centered sustainable livelihoods approach as a research paradigm in R4D, researchers may be more successful in producing knowledge that is useful to entrepreneurial smallholder farmers. Without such rethinking, traditional scientific approaches and logic may limit the contribution that agricultural R4D can make toward the achievement of the Millennium Development Goals of halving extreme hunger by 2015 and improving the livelihoods of all
In field N transfer, build-up, and leaching in ryegrass-clover mixtures
Two field experiments investigating dynamics in grass-clover mixtures were conducted, using 15N- and 14C-labelling to trace carbon (C) and nitrogen (N) from grass (Lolium perenne L.) and clover (Trifolium repens L. and Trifolium pratense L.). The leaching of dissolved inorganic nitrogen (DIN), as measured in pore water sampled by suction cups, increased during the autumn and winter, whereas the leaching of dissolved organic nitrogen (DON) was fairly constant during this period. Leaching of 15N from the sward indicated that ryegrass was the direct source of less than 1-2 percent of the total N leaching measured, whereas N dynamics pointed to clover as an important contributor to N leaching. Sampling of roots indicates that the dynamics in smaller roots were responsible for N and C build-up in the sward, and that N became available for transfer among species and leaching from the root zone. The bi-directional transfer of N between ryegrass and clover could however not be explained only by root turnover. Other processes like direct uptake of organic N compounds, may have contributed
15Nitrogen uptake from shallow- versus deep-rooted plants in multi-species mixtures and monoculture grassland
Only few studies have explored the importance of functional diversity in temperate agricultural grasslands in relation to nitrogen (N) uptake. This study investigates the consequence of growing deep-rooted plants together with grass-clover mixtures in terms of N uptake efficiency from deep soil layers. The objective was to compare the N uptake of the shallow-rooted grassland species Lolium perenne and Trifolium repens; and the deep-rooted species Cichorium intybus and Medicago sativa in monocultures and mixtures. We hypothesized that growing deep-rooted plant species in mixture with shallow-rooted species increases the N uptake from deep soil layers partly through competition. A 15N tracer study was carried out with 15N enriched ammonium-sulphate placed at three different soil depths (40, 80 and 120 cm). To recover 15N, above-ground plant biomass was harvested after 10 days. We described the decline of 15N uptake with depth by using an exponential decay function. The studied plant communities showed the same relative decline in 15N uptake by increasing soil depths, but different capacities in total 15N uptake. Monoculture L. perenne foraged less 15N in all depths compared to the other four plant communities. The relative 15N uptake of individual plant species grown in mixture decreased stronger with depth than in monoculture. Thus, both findings rejected our hypothesis
15Nitrogen transfer from legumes to neighbouring plants in multi-species grassland
This study investigates the N transfer from legumes to neighbouring plants, grasses, legumes and herbs in a temperate grassland. In a field experiment white clover (Trifolium repens), red clover (Trifolium pratense) and lucerne (Medicago sativa) were leaf-labelled with 15N enriched urea. The 15N tracer was measured in above-ground plant tissue of eight neighbouring plants in two subsequent harvests in 2008. The three legumes donated 15N to all neighbouring plants, of which grasses, white and red clover were strong receivers. Results show that N transfer increases with N application and from the 1st to the 2nd cut
Data assimilation in integrated hydrological modeling using ensemble Kalman filtering:evaluating the effect of ensemble size and localization on filter performance
Groundwater head and stream discharge is assimilated using the ensemble
transform Kalman filter in an integrated hydrological model with the aim of
studying the relationship between the filter performance and the ensemble
size. In an attempt to reduce the required number of ensemble members, an
adaptive localization method is used. The performance of the adaptive
localization method is compared to the more common distance-based
localization. The relationship between filter performance in terms of
hydraulic head and discharge error and the number of ensemble members is
investigated for varying numbers and spatial distributions of groundwater
head observations and with or without discharge assimilation and parameter
estimation. The study shows that (1) more ensemble members are needed when
fewer groundwater head observations are assimilated, and (2) assimilating
discharge observations and estimating parameters requires a much larger
ensemble size than just assimilating groundwater head observations. However,
the required ensemble size can be greatly reduced with the use of adaptive
localization, which by far outperforms distance-based localization. The
study is conducted using synthetic data only
Yields and qualities of pigeonpea varieties grown under smallholder farmersâ conditions in Eastern and Southern Africa
Pigeonpea is one of the few crops with a high potential for resource-poor farmers due to its complementary resource use when intercropped with maize. A three year comprehensive comparative study on the performance of six pigeonpea (Cajanus cajan) varieties on farmersâ fields in Eastern and Southern Africa where intercropping with maize is normal practice, was undertaken. The varieties were tested for accumulation of dry matter (DM), nitrogen (N) and phosphorus (P) in all above-ground organs for three years under farmersâ conditions. The study revealed that the latest introduced ICEAP 00040 outperformed all the other tested varieties (ICP 9145; ICEAP 00020, ICEAP 00053, ICEAP 00068, and a local variety called âBabati Whiteâ) under farmer-managed conditions. The harvest indices (HI), ranging from 0.08-0.15 on dry matter (DM) basis, were relatively low and unaffected (P>0.05) by the environmental variation. The N harvest index (NHI) was 0.28 and P harvest index (PHI) was 0.19. The better responses of ICEAP00040 to favourable conditions could however only be realised in a minority of cases as yields generally were low. These low yields are still a major challenge in African smallholder agriculture as pulses play an important role in soil fertility maintenance as well as in the household diets
Afrika â Fremtidens Ăkologiske Kontinent?
Afrikanske bønders forbrug af fossil energi er lavt â og deres forurening med nitrat, sprøjtegifte og klimagasser er begrĂŚnset
Nitrogen transfer from forage legumes to nine neighbouring plants in a multi-species grassland
Legumes play a crucial role in nitrogen supply to grass-legume mixtures for ruminant fodder. To quantify N transfer from legumes to neighbouring plants in multi-species grasslands we established a grass-legume-herb mixture on a loamy-sandy site in Denmark. White clover (Trifolium repens L.), red clover (Trifolium pratense L.) and lucerne (Medicago sativa L.) were leaf-labelled with 15N enriched urea during one growing season. N transfer to grasses
(Lolium perenne L. and xfestulolium), white clover, red clover, lucerne, birdsfoot trefoil (Lotus corniculatus
L.), chicory (Cichorium intybus L.), plantain (Plantago
lanceolata L.), salad burnet (Sanguisorba minor L.)and caraway (Carum carvi L.) was assessed. Neighbouring plants contained greater amounts of N derived from white clover (4.8 gm-2) compared with red clover (2.2 gm-2) and lucerne (1.1 gm-2). Grasses having fibrous roots received greater amounts of N from legumes than dicotyledonous plants which generally have taproots. Slurry application mainly increased N transfer from legumes to grasses. During the growing season the three legumes transferred approximately 40 kg N ha-1 to neighbouring plants. Below-ground N transfer from legumes to neighbouring plants differed among nitrogen donors and nitrogen receivers and may depend on root characteristics and regrowth strategies of plant species in the multi-species grassland
Market Integration Shape Organic Farmersâ Organisation
Increasing consumption of organic products in globalised food chains will require the involvement of thousands more smallholder farmers in many regions of the world. A study of Egypt, China and Uganda identified the three key factors of property rights regimes, cultural differences and social organisation as determents of the supply chain organization and farmersâ degree of direct integration in the export markets. Patterns are emerging where smallholder farmers are being socially and economically linked to larger farmers who may do some processing before the raw materials are handed over to the contracting company. Where transactions costs are high, local communities may develop and contract out the land directly to exporting companies who farm using employees. Four organisational patterns are identified which each leads to different types of livelihood benefits for the producers; preliminary results indicate that income and a reliable market access is the dominant benefits
Sustainable bioethanol production combining biorefinery principles using combined raw materials from wheat undersown with clover-grass
To obtain the best possible net energy balance of the bioethanol production the biomass raw materials used need to be produced with limited use of non-renewable fossil fuels. Intercropping strategies are known to maximize growth and productivity by including more than one species in the crop stand, very often with legumes as one of the components. In the present study clover-grass is undersown in a traditional wheat crop. Thereby, it is possible to increase input of symbiotic fixation of atmospheric nitrogen into the cropping systems and reduce the need for fertilizer applications. Furthermore, when using such wheat and clover-grass mixtures as raw material, addition of urea and other fermentation nutrients produced from fossil fuels can be reduced in the whole ethanol manufacturing chain. Using second generation ethanol technology mixtures of relative proportions of wheat straw and clover-grass (15:85, 50:50, and 85:15) were pretreated by wet oxidation. The results showed that supplementing wheat straw with clover-grass had a positive effect on the ethanol yield in simultaneous saccharification and fermentation experiments, and the effect was more pronounced in inhibitory substrates. The highest ethanol yield (80% of theoretical) was obtained in the experiment with high fraction (85%) of clover-grass. In order to improve the sugar recovery of clover-grass, it should be separated into a green juice (containing free sugars, fructan, amino acids, vitamins and soluble minerals) for direct fermentation and a fibre pulp for pretreatment together with wheat straw. Based on the obtained results a decentralized biorefinery concept for production of biofuel is suggested emphasizing sustainability, localness, and recycling principle
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