Browsing by Subject "Wassernutzungseffizienz"

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A study of pasture cropping as an alternative cropping system for sub-saharan Africa
(2020) Orford, Rohan; Asch, Folkard
With food security and soil degradation being a major concern and hurdle in the development goals of sub-Saharan Africa (SSA), there has been and continues to be an attempt to find an alternative cropping system to conventional monocropping that rehabilitates soils whilst increasing productivity and efficiency of the subsistence cropping system. Such a cropping system needs to be realistically adoptable within the SSA social and ecological constraints. An alternative Australian winter rainfall relay cropping system coined pasture cropping (PaCr) was identified as an option that may surmount some of these limitations.This research involved completing a field trial through to model scale introductory assessment of the water dynamics in PaCr and the implications thereof in yield, water use efficiency (WUE) and competition for water; ultimately assessing the potential of PaCr in SSA. PaCr was adapted to an intercropping system for SSA summer rainfall conditions. The three treatments included the representative subsistence crop cowpea (Vigna unguiculate) and a common indigenous pasture (Eragrostis curvula) and an additive PaCr setup of cowpea directly seeded into pasture in water limited (rainfed) field trials in Pretoria, South Africa between 2013-2015. The DM yields of PaCr were 17% and 293% higher in both seasons compared to the conventional cowpea monocrop yield. When comparing PaCr yield to conventional pasture, there was a 12% and 89% higher yield in both seasons compared to the conventional pasture monocrop yield. The greater yield advantage in 2015 with the limited rainfall indicates that PaCr was most advantageous in terms of DM yield in a drier year which is a time of greatest risk and food insecurity. PaCr was also more WUE in both seasons, being significantly higher than the cowpea monocrop in 2015. Competition also showed a higher degree of competitiveness by cowpea in the wetter 2013-14 season and lower competitive ability in the drier 2015, whereas pasture showed little competitive response in 2013-14 and attaining significantly higher yields than the monocrop in 2015. The results of the field trials were used to adapt the University of Pretoria’s Soil Water Balance (SWBsci) crop model to simulate an intercropping system. Observed field results were compared to simulated results and statistical goodness of fit indicators were assessed, concluding that with all the variations of season and systems, the results were acceptable as an inaugural adaptation of the Soil Water Balance model. Other relevant crop water use parameters were extrapolated from the simulated data allowing for a more complete insight into the field trials. With the adapted SWBsci model, 14-year simulations were run in three different climates and on three different soil types for all three cropping systems to map out the viability of PaCr across an aridity index continuum as a reference for further application in research or in industry and to stress test SWBsci. Results demonstrated that PaCr was only advantageous in dry sub-humid to humid conditions on clay-loam to sandy soils, whereas pasture was dominant in more semi-arid conditions on the three different soils. Cowpea only performed better on clay soils in dry-sub humid to sub humid conditions. These advantages are attributed to differing plant water availability at various root depths suiting growth and/or competition of either one or both crops. These plant water availability differences were determined by water holding capacity of various soil types and rainfall volumes. From a WUE perspective, the pasture and PaCr did have a higher WUE but with the extreme variation in rainfall there was no significant difference. But pasture and PaCr both had a very high WUE in arid to semi-arid conditions due to the deeper roots of pasture accessing stored soil water. Competition also showed insignificant results due to the variation in the rainfall. However, in more arid to semi-arid conditions on clay-loam and sand competition outweighed facilitation thus resulting in land equivalent ratios (LER) of below 1, whereas on clay for the same aridity levels the average LER was greater than one. This was attributed to cowpea have a better competitive ability when clay water holding capacity confined plant available water to the top soil layers. The converse is true in the dry sub-humid conditions and wetter conditions because LER was less than one on clay soils while being greater than one on clay-loam and sand. This was attributed to the lower water holding capacity of sand spreading the plant available water through the profile allowing for niche root partitioning to be effective. For subsistence farmers, PaCr out-yielded the cowpea monocrop in arid conditions on all three soil types and on clay in semi-arid conditions. In the wetter dry sub-humid conditions, PaCr out-yielded cowpea on sand. In the wet sub-humid conditions PaCr does well on clay-loam and sand, but cowpea yields under these conditions are more than adequate to make the choice of PaCr debatable form a yield point of view. However, if soil rehabilitation is a necessity in the sub-humid areas, this makes PaCr a very realistic option.
Role of irrigation water pricing in sustainable water resources management along the Tarim river, Northwest China
(2016) Mamitimin, Yusuyunjiang; Doluschitz, Reiner
The main objectives of the study are to explore whether irrigation water pricing can lead to efficient water use in agriculture along the Tarim River. To understand land and water use development and driving forces along the Aksu-Tarim Basin, a workshop was conducted in Urumqi which is capital city of Xinjiang Uyghur Autonomous Region. Local experts from different research disciplines as well as relevant stakeholder participated in the workshop. Besides, data were collected and analyzed from preselected sources such as statistical yearbook and government’s official document. Research results embedded in the first article revealed that there was a huge land expansion and increase in water use for agriculture during the period from 1989 to 2011. The results also indicate that interaction of vast population growth, positive price development, agricultural profitability increase, government’s afforestation program (Grain for Green) and insufficient control of land expansion were the main driving forces for those developments. Farmers’ behavior towards the changes of irrigation water pricing is one of the important factor determining efficiency of water pricing to elicit water conservation and demand reduction. Therefore, a total of 257 farm household interviews were conducted, of which 128 served to find out farmers’ responses towards the changes of water pricing in different parts of Tarim River in July and August 2012. The results of statistical analyses are presented in the second article. Results show that only less than half of the interviewed farm households would react to increased water prices with proper changes of their farming practices leading to a more efficient water use. Results also show that increasing water prices encourage the farmers to shift their irrigation from surface water to groundwater which may result in further environmental problems. In the second article it is not possible to access the impact of different water price levels and changes in the water pricing practices because of its technicality and complexity. Besides, an irrigation water pricing reform needs to consider institutional aspects which are usually ignored in research on water pricing. Therefore, an innovative approach, Bayesian network modeling, was employed to find out the effects of different water price levels, changes in water pricing practices, and other agricultural policy options on the water use efficiency along the Tarim River. Results presented in the third article show no significant impact of water prices increased by 0-50% on water use efficiency. Solely an increase of 100% may have a relevant positive effect on water use efficiency. The model results also reveal that water pricing may provide a promising option to increase water use efficiency provided that volumetrically measuring systems, subsidies for water saving technologies, and technical support are available. The fourth article discusses the economics of cotton production and land use changes along the Tarim River from 1989 to 2009 using data from official statistical yearbooks. The results of a trend analysis indicate that the land area of cotton increased. In contrast, the area of other crops slightly decreased. Results of comparative advantage index of cotton production show that most farmers in the upper stream are more efficient in cotton production compared to farmers of the lower stream, whereas farmers in Xinjiang Production and Construction Corps are more efficient than farmers outside the Xinjiang Production and Construction Corps. The overall results of the study indicate that irrigation water pricing is not the best option to achieve an efficient water use in agriculture along the Tarim River. It requires additional adjustments and supportive agricultural policies such as the availability of volumetric measuring systems, subsidies for water-saving technologies, technological support for farmers, as well as a further institutional reform. Besides, special attention should be given to the protection of groundwater resources, especially when water prices increase. Furthermore, additional research is needed to examine the impacts of water pricing on farmers’ welfare, and the role of transferable water rights and water user associations in terms of an efficient water use along the Tarim River.