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Agrometeorology

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Browsing Agrometeorology by Subject "Air temperature."

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    Assessment of vulnerability of cattle farming to climate variability and change in South Africa.
    (2021) Masemola, Makgethwa Jillie.; Savage, Michael John.; Tongwane, Mphethe Isaac.
    Livestock are dependent upon weather for their comfort and food supplies. Sometimes, adverse weather conditions can cause production losses, especially if experienced during critical stages of growth. Heat stress is a major cause of production losses in the dairy and beef industries. Heat stress occurs when the temperature of the environment increases above the comfort zone of cattle as a result of solar irradiance. Heat stress decreases grazing and feed intake in cattle, while drought can limit pasture availability for grazing cattle. The temperature-humidity index (THI), a combination of air temperature and relative humidity, was used to determine the influence of heat stress on the productivity of cattle. The aim of the study was to investigate the air temperature and relative humidity conditions over South Africa accountable for high THI values for cattle farming for the period 1985 to 2015. The standard precipitation index (SPI) and normalised difference vegetation index (NDVI) at three months were computed to assess the soil moisture conditions and vegetation greenness for the season with high THI averages. The THI data analysis was performed seasonally, using a 15-year average and daily values from 75 weather stations in South Africa. Monthly rainfall data from 192 weather stations were used to compute SPI at three months. The NDVI used MODIS satellite information to create vegetation images for the three summer months. Results indicated summer as a season when cattle are vulnerable to heat stress. The periods (2005/06, 2007/08, 2012/13, 2013/14) experienced high seasonal averages (THI > 80) compared to the remaining years. Daily THI extremes were prevalent in February in South Africa. The SPI results indicated that the North West, the western Free State and east of the Eastern Cape provinces were vulnerable to dry conditions for the four summer periods. The NDVI results indicated that the eastern and coastal parts of South Africa were areas of high vegetation activity and greenness for all the summers. The Northern Cape, Limpopo, North West and Free State provinces had vegetation that was vulnerable to dry conditions. Heat stress and a healthy vegetation activity were a problem for the Northern Cape and Limpopo provinces, while KwaZulu-Natal and Mpumalanga had heat stress as their only challenge. The northern and eastern parts of South Africa were heat stress areas with air temperature as the main driver in THI. New smaller areas were developing as heat stress zones, and areas that were identified as heat stress zones in the past were increasing in size for South Africa. Natural grazing areas indicated no significant relationship with THI but showed a relationship with SPI. Cattle farmers situated in the heat stressed regions of South Africa and new heat stress developing areas need to take the necessary precautions to make profitable decisions for their cattle production.
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    Temperature dynamics within a low-cost aquaponic system and the possibe effects of climate change.
    (2019) Mkhize, Minenhle Godslove.; Clulow, Alistair David.; Taylor, Simon Michael.; Lagerwall, Gareth.
    The agricultural sector is facing impeding challenges due to climate change. There is enough evidence showing that climate change has a significant impact on agricultural production. Marginalized communities that lack financial resources and depend on agricultural crop production, are the most vulnerable to climate change effects, which further exacerbates 5 their food insecurity. Existing literature hypothesizes that aquaponics, using Tilapia, has potential in addressing climate change effects in agriculture. However, the low average winter temperature hinders successful adoption of low-cost aquaponic systems using Tilapia fish. The implication of cool conditions (South African temperatures) are more extreme for a low-cost, poorly resourced aquaponic users because they lack temperature regulation 10 systems to maintain optimal temperatures and are simply subject to the surrounding environmental conditions. Therefore, the purpose of this study was to understand the temperature dynamics of a low-cost aquaponic system and the possible effects of future climate change. A study was conducted at KwaDeda, a poor rural community in the Ndwedwe area of 15 KwaZulu-Natal. The two objectives were to (1) understand how the surrounding environmental air temperature affects the water temperature of a low-cost aquaponic system and, to (2) assess the implications of future climate change on a low-cost aquaponic system. Two weather stations (22 km apart) were installed, one to measure hourly environmental air temperature conditions and the other to measure the conditions within the plastic tunnel of 20 a low cost aquaponic system (from June – November 2019). The environmental air temperature had no immediate relationship with water temperature. However, there was an observed lag of 4 hours from the environmental air temperature peak to water temperature peak, which varied slightly with seasonality. The conditions within the tunnel were generally hotter than the outside environmental conditions during the day, 25 however, at night, the tunnel air temperature dropped to be the same and sometimes even lower the outside environmental temperature. The air temperatures in winter and resulting water temperatures of the low-cost aquaponic system was well below the optimum range for Tilapia (22-32 °C). Low-cost systems provide limited means to control water temperature. Therefore, further investigation into low-cost methods to reduce the cooling of the tunnels 30 at night, which later results in cooling of the water, is required. The projected future climate was shown to be both advantageous and disadvantageous for the low-cost aquaponic system. The projected increase in average air temperature due to climate change will be positive for South African conditions, which are generally quite cool for Tilapia. However, extreme weather conditions such as intense storms, high wind speed and hail, that are predicted with climate change, may be a threat to low-cost aquaponic infrastructure. Research into improving the design of low-cost tunnels that can withstand adverse weather conditions is recommended.