Curated Content

The 2013 AAEA & CAES Joint Annual Meeting in Washington, DC will offer AAEA members, CAES members, and other applied economists a chance to interact and learn over the course of the three day meeting on August 4-6. This year’s meeting features a large amount of educational content including:

More than 150 educational sessions

Over 200 posters on display, with opportunities to interact with their authors

Multiple plenary sessions each day, featuring high-profile speakers

Common research topics include:

International development

Climate change

Biofuels

Linkages between food and health

The Farm Bill

Land use and water resource issues

Regional economics

Business economics

Behavioral economics

The meeting will also feature a number of chances for attendees to connect and network at the welcome and closing receptions, receptions for specific Sections of AAEA, and evening gatherings organized by universities and government agencies.

Maize (Zea mays L.) is the major grain crop in South Africa where most subsistence farmers still plant landraces. The objective of this study was to compare two landrace selections of maize with two hybrids popular among small-scale farmers in KwaZulu-Natal, for seed performance and water stress tolerance during seedling establishment. Two variations of a local landrace, white (Land A) and dark red (Land B), were compared to two hybrids, SC701 and SR52. Standard germination test and electrical conductivity were used to assess seed quality under laboratory conditions. Seedling emergence was performed in seedling trays using pine bark at 25% and 75% field capacity (FC), respectively, over a period of 21days. All seed types showed high germination capacity (>93%). There were highly significant differences (p<0.001) among seed types with respect to daily germination and germination velocity index (GVI). Landraces germinated slower than the hybrids. Landraces showed a 20% better root length and 41% lower electrolyte leakage than hybrids. There were differences (p<0.001) in seedling emergence between 25%FC and 75%FC. Hybrids showed better emergence at 75% FC. At 25% FC seedling emergence was drastically reduced (>5% in all varieties). Hybrids emerged faster than the landraces in both water regimes. Landraces performed better than hybrids under stress conditions. This study showed that landraces may have the same viability as hybrids and a better tolerance to stress during early establishment of the crop.

Agriculture in Namibia plays a critical role in the formal and informal economy supporting 70% of the population directly or indirectly through employment and income generation. The agricultural sector in Namibia contributes over 10% to the GDP of which 75-80% can be attributed to livestock farming. The livestock industry accounts for 90% of all agricultural production in Namibia with approximately 60% of households owning cattle, including nearly 40% of poor households. Crop production activities in Namibia are limited, mainly due to the arid climate and low rainfall patterns. Rain-fed crops include pearl millet, sorghum and maize are the most dominant crops grown in Namibia. The average yield for these crops ranges from 24.7 ton for pearl millet, 72,438 for maize and 14,819 for wheat. The dependence on rain-fed agriculture increases the vulnerability of farming systems and predisposes rural households to food insecurity and poverty. However, the reduction in crop yields will have devastating impacts on food security at both national and household levels. Under the current conditions, the agriculture sector in Namibia needs to grow by 4% a year to meet the food requirements for the expanding population. In light of these challenges, Namibia needs to adapt its agricultural practices and increase the resilience of livelihoods to be able to withstand the challenges posed by climate change to sustain development and growth of the country.

The eyes of some 180 000 Namibia’s communal crop farmers  are firmly focused on the implementation of the European Union’s Conservation Agriculture Project for Namibia via the International Food Organisation (FAO) after N$40 million was approved for this proven practice. This will be emphasised in strong terms after the Ministry of Environment and Tourism has indicated that it will celebrate the World Day to Combat Desertification on June 17 in Omuthiya with special focus on conservation agriculture (CA). 

Scientific trials on farms on Namibia-specific Conservation Agriculture or Tillage (NSCA) over the last ten years have been revolutionising rain fed grain crop yields to the extent that Namibia could become self sufficient in millet and maize production in the not too distant future despite the effects of climate change.

This is the expert opinion of independent consultant and acknowledged conservation agriculturalist beyond Namibian borders, Rod Davis. “Far from our crop production being liable to drop by 50% because of climate change according to the ‘experts’, we are presently seeing millet yields increasing from the national average of 300 kilogrammes per hectare to 3000 kilogrammes and more even during the current severe drought. Would interested and affected parties, including ministries, please take note. (CA) Conservation Agriculture practises, such as no-till, that work in other countries don’t work here because of our low and erratic rainfall and degraded soils,” says Davis.

He adds that Conservation Tillage (CT) is specifically designed for Namibian conditions and it really works and its benefits extend to soil degradation reversal; farmer livelihood improvement; food security; combating deforestation and labour saving per unit of yield, the list goes on. The system employs, as part of the package, Namibian unique Ripper Furrowing (RF) tillage technology. RF is a combined operation where the implement rips 30 centimtres deep, shattering the hard pan caused mainly by the compacting effect of disc harrowing, whilst at the same time forming water harvesting furrows. The rip line is at the base of the furrow where the crop is planted while the furrow sides deliver 75% more moisture to the crop. Crop rotation with legumes is also part of the system with indigenous cowpea, bambara nut and ground nut which are all highly nutritious as well as marketable.

“To us and also to the rapidly growing number of CT/CA farmers, to whom we have introduced the system, there is no need to spend any more time dithering and wondering what to do next! The system definitely works really very well whether small or large scale.

However; some problems need to be addressed, as follows:

RF alone, without the rest of the package, will not improve the soil. Yields will increase initially with deeper rooting finding leached nutrients plus the additional moisture. Therefore, in the medium term yields are likely to drop back meaning farmers will become disillusioned,

Presently there are no less than ten Namibian based organisations involved in CT/CA, six directly and four indirectly with some variances in approach and methodology. To ensure that farmers are basically told the same thing by these initiatives, a more associative approach between these organisations for better harmonised introduction and adoption should be considered. This would hopefully also assist in more collaboration and less competition as at present,CT/CA should be regarded as a continuum with changes made when needed and recognised, and of course agreed upon. For example Conservation Agriculture Namibia (C.A.N.) have introduced what is called the 2,2,2, crop rotation system where two rows of a grain crop next to two rows legume and two rows grain crop are planted (grains are either indigenous mahangu or short season drought resistant maize). This works well in that nitrification by the legume adjoining the mahangu or maize is quicker.

On the farmers’ side, the most important element is, as always, management. This is the golden rule for the extraordinary high yields being achieved.

Namibia is one of the most arid countries south of the Sahara. Around 70 % of the population lives in rural areas. Fishery, tourism and agriculture form the basis of the country's economy. However, the economy is held back by low demand for domestic products as well as high transport costs and competition with products from South Africa. Climatic variability is a common phenomenon in Namibia, exhibited by persistent droughts, and unpredictable and variable rainfall and temperatures. Land degradation - soil erosion, bush encroachment, deforestation - and desertification are increasingly a threat to agricultural productivity. Climate change reports predict an increase in temperature and a lower amount of rainfall. Changing patterns and intensity of rainfall are likely to increase the rate of soil erosion, affecting crop production and livestock. An increased incidence and severity of extreme weather events such as flooding will worsen soil erosion and destroy crops. Climate change will affect the agricultural yield directly through changes in temperature and precipitation, and indirectly through changes in soil quality, pests, and diseases. In response this project aims at enhancing the adaptive capacities of farmers, pastoralists and natural resource managers to climate change in agricultural and pastoral systems. The project is working to develop and pilot a range of effective coping mechanisms for the reduction of the farmers' and pastoralists' vulnerability to climate change and variability. The following coping mechanisms were chosen for the project intervention: Improved seeds, Aquaculture, Livestock, Rainwater harvesting, Conservation agriculture, Drip irrigation, Buffalo grass. As target group 500 farming households were chosen. 

No information is available on responses of South African taro landraces to water stress. The objective of this study was to evaluate the responses, and mechanisms thereof, of taro to water stress under controlled and field conditions. Taro landraces were collected from rural areas in KwaZulu-Natal, South Africa. A pot trial was planted in tunnels at the University of KwaZulu-Natal with two factors: three landraces and water stress (NS – no stress, IS – intermittent stress and TS – terminal stress), replicated six times. For NS, soil water content (SWC) was maintained at 75% field capacity (FC). IS involved watering pots to 75% FC during crop establishment, and allowing SWC to deplete to 30% FC during the vegetative stage, before returning to 75% until harvest maturity. For TS, SWC was maintained at 30% FC for the entire growing period. Field trials were planted in October 2010, with irrigation (full irrigation versus rainfed) as a main factor and landrace type as sub-factor, replicated three times. SWC was monitored weekly. Emergence, plant height, leaf number, leaf area, LAI, vegetative growth index (VGI) and stomatal conductance (SC) were determined weekly. Results from both pot and field trials showed that taro landraces were slow to emerge (~49 days). There were significant differences (P<0.001) between landraces with respect to final emergence. Taro growth (plant height, leaf number and leaf area), for both trials, was shown to be significantly (P<0.05) reduced by water stress. Under field conditions, SC, LAI and VGI were significantly (P<0.05) lower under rainfed conditions compared with irrigated conditions. It is concluded that emergence and vegetative growth parameters of KwaZulu-Natal taro landraces are sensitive to water stress. Data from this study will be used to calibrate AquaCrop and presented as a possible option to manage taro under dryland and irrigated conditions in the warm subtropical areas of South Africa.

Historically, traditional cropping systems are based on diversification, thus making a significant contribution to food security for the household. Intercropping may offer farmers the opportunity to mimic this diversity. The aim of this study was to evaluate the productivity of a taro-bambara intercrop. The intercrop combinations were 1:1 and 1:2, compared with taro and bambara sole crops. Growth parameters and yield components were determined separately for each crop. Thereafter, land equivalent ratio (LER) was calculated to evaluate the productivity of the intercrop. Plant height of taro, as the main crop, was not significantly affected by intercropping. However, leaf number was significantly affected (P<0.001). Intercropping taro resulted in reduced leaf number compared with the sole crop; leaf number in response to the 1:2 intercrop was significantly lower than that of 1:1 intercrop. Bambara growth was significantly (P<0.05) affected by intercropping in that plants were taller and had more leaves when intercropped with taro. Taro yield was not significantly affected by intercropping, although yield generally decreased under intercropping compared with the sole crop. Bambara yield was also not significantly affected by intercropping. The LER showed that intercropping was more productive than sole cropping. The 1:1 intercrop had a LER of 1.71 compared with 1.36 for the 1:2 intercrop. It is concluded that although intercropping had variable effects on the growth of both taro and bambara, there was an agronomic advantage to intercropping.

AquaCrop is a crop model that simulates yield response to water developed by FAO and is appropriate to consider effects where water is the limiting factor for crop production. AquaCrop was calibrated for amaranthus (Amaranthus cruentus L. ex Arusha), a leafy vegetable, and taro (Colocasia esculenta (L.) Schott.), a wetland perennial, with an edible starchy corm as a tuber crop. The weather datasets were obtained from the climate database at Agricultural Research Council-Institute of Soil, Climate and Water in Pretoria for specific sites and years of the trials. The first step in the model is to select the correct type of crop, create a new crop and name it. Observed soil parameters from the experimental sites were used to create soil files in AquaCrop; the model is sensitive to amount of water available in the soil between field capacity and permanent wilting point. The crop parameters under optimal water availability were adjusted according to observations from field trials conducted for each crop. The first parameter checked was canopy cover, representing the expansion of the leaf canopy under non-limiting conditions, where the maximum value, CCx, (90% for amaranthus and 78% for taro) and the time take to reach CCx were needed. The total length of the cropping season should be checked and also time to the start of senescence. However, for the leafy vegetable this was not necessary as the crop was harvested while the leaves were green. The effect of water stress must be included via the Ks factor for water stress according to stomatal closure at a specific soil water availability, as measured in the field trials. The water productivity normalised for ETo and CO2 concentration (32 g m-2 for amaranthus and 15 g m-2 for taro) was calculated from field data of biomass accumulation and transpiration standardised for ETo. The reference harvest index (HIo) was 85% for amaranthus and 83% taro, respectively. Once the model is calibrated with data from single sites, it must be verified with independent data from different sites and/or series of experiments. The calibrated AquaCrop model will be used to promote the introduction of these underutilised vegetables on irrigation schemes since optimal irrigation strategies can be developed. Best management practices, soil types, sowing dates and locations can be selected from model runs at a range of sites.

Intercropping involves the cultivation of two or more crops on the same field in both space and time. It is a farming practice that has existed throughout history and one which mimics natural diversity. Intercropping has several advantages over monocropping which include improved resource utilization of light, water and nutrients, as well as yield stability over time. It is a practice that historically contributed towards food security within communities. It offers a sustainable alternative to the more widely practiced monocropping. However, it has been widely regarded as a primitive practice and this has created a scenario whereby there was scant research done on intercropping.