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May 2018



ARTICLE 1/2 THE NATURE OF SOIL ACIDITY AND IT’S DIAGNOSIS Acid soil conditions restricting crop growth occur widely in the eastern parts of South Africa. In the higher rainfall areas, soils are often naturally acidic; however, human intervention may accelerate acidification. It is worth noting that soil acidity problems are by no means unique to this country: worldwide, approximately 30% of the land available for cultivation is acidic. Farmers frequently have difficulty in getting to grips with the various soil acidity parameters listed in soil test reports, and furthermore, may be presented with conflicting advice regarding the use of products such as lime and gypsum. The purpose of these articles is to provide scientifically sound and practically useful answers to questions such as: “What exactly is soil acidity?”, “How does it impact crops?”, and “How is it best managed?” SOIL ACIDITY – WHAT IS IT, AND WHAT CAUSES IT? In order to gain a working understanding of soil acidity, there is a need to touch on some basic soil chemistry. Clays and organic matter in the soil carry a negative charge. In a soil that is not acidic, this negative charge is balanced by the positive charge on certain plant nutrients, in particular, calcium (Ca++) magnesium (Mg++) and potassium (K+). As soils acidify, concentrations of other non-nutrient elements, in particular hydrogen (H+) and aluminium (Al+++), as well as manganese (Mn++), increase, and they take the place of nutrients such as calcium and magnesium on the clays and organic matter (Figure 1). Under non-acidic conditions, the aluminium and manganese are contained in the clay and other soil mineral particles, but as acidity increases, clay edges start dissolving, releasing soluble aluminium and manganese into the soil. Importantly, from the perspective of managing soil acidity, it is the soluble aluminium, and sometimes manganese, which are the most important growth-limiting factors in acid soils. Furthermore, it must be borne in mind that pH measures only the concentration of hydrogen in the soil, and not that of aluminium and manganese. These considerations are of cardinal importance in terms of the development of economically sound recommendations for the correction of acidity problems. What causes soils to acidify? Although, as noted earlier, acid soils occur widely in nature, the following human activities may markedly accelerate acidification: Acid rain, resulting from atmospheric pollution by industry. This has been shown to be a major contributory factor in some Highveld areas. The use of nitrogenous fertilizers, particularly when applied in excess of immediate crop requirements. The removal of basic nutrients (calcium, magnesium and potassium) in harvested crops and animal products. Accelerated decomposition of soil organic matter as a result of tillage. SOIL ACIDITY – EFFECTS ON CROP GROWTH The effects of soil acidity on crop growth tend to be insidious, in that it is in the root zone where the major impact occurs. Damage caused to the root system and the unfavourable soil chemistry associated with excessive acidity are translated into poor crop growth, with there frequently being no classical…

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Dr Mart Farina consulting soil scientist

By Conferences and Training No Comments

Dr Mart Farina started his career as a Land Development Officer in Rhodesia and then worked as a soil fertility researcher in the South African Department of Agriculture and the Agricultural Research Council from 1965 to 1998. Since then, he has consulted to Omnia Fertilizer, the FAO in Ethiopia, Nordic Fertilizers in Central America, and to government agencies and individual farmers in Kenya, Tanzania, the DRC, Zambia, Madagascar, Malawi, Zimbabwe and the Republic of Guinea. During the course of his career Mart has authored or co-authored 66 refereed scientific papers, 23 of which were published in international journals. In the interests of technology transfer to the agricultural industry Mart has also published over 50 semi-scientific and popular articles and addressed some 300 farmer’s days; he has also presented over 70 papers at scientific conferences and technical symposia. Mart was a Research Fellow at the University of Georgia, U.S.A., during 1978 and has participated in 10 international conferences on soil fertility, on five occasions as an invited speaker. Mart has been the recipient of numerous awards including six from the Fertilizer Society of South Africa (FERTASA), the BP Scholarship in Agriculture, the Gold Medal for Research from the South African Society of Crop Production, and the Sanachem Prize. In 1988 and 2005 was the Natal Agricultural Writer’s Association Agriculturist of the Year, in 1984 the National Maize Producer’s Maize Researcher of the Year, and in 1994 the Summer Grain Centre’s Researcher of the Year. Mart served as the standing member for Africa, on the International Steering Committee for Symposia on Plant-Soil Interactions at Low pH from 1993 until 2001. Mart has Honorary Membership of the South African Society of Crop Production and is a 40-year Emeritus Member of the Agronomy Society of America and the Soil Science Society of America. Contact details:  

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By Biostimulants, Conferences and Training, Soil Acidity No Comments

Ruth Rhodes previously worked for The South African Sugar Research Institute (SASRI) as a soil scientist and is now a private consultant, delivered a well balanced and objective presentation on the definition of soil health, highlighting some prevalent factors affecting soil health and methods of quantifying soil health. Rhodes initiated the concept of soil health by highlighting “how every soil tells a story” as illustrated below where two soils that started out identically thirty years ago ended up so different due to land use and management: The “term soil health” today is used interchangeably with the terms “soil quality” and “soil condition” and there are various definitions that are used to describe soil health: A state of a soil meeting its range of ecosystem functions as appropriate to its environment. Soil health / quality describes soils that are not only fertile but also posses adequate physical and biological properties to “sustain productivity, maintain environment quality and promote plant and animal health”- Doron 1994. “how well soil does what we want it to do” – USDA Rhodes pointed out that there are many other definitions however we should want our soils to support and  grow optimally yielding crops, “forever” without harming the environment. The soil food web may be used as the starting point in assessing soil health, however there are over forty different factors that determine soil health which can be grouped into biological factors, physical factors, chemical factors and nutritional factors. Rhodes aptly likened these groups of factors to being the pieces of a puzzle and that if on piece was missing then the puzzle is incomplete: Soil health shouldn’t be viewed in terms of biology only as it is comprised by a whole range of different factors, of the these there are only two inherent qualities that we can’t really control and aren’t affected by management easily; soil depth and texture. They are determined by the factors of soil formation such as climate, topography, vegetation, parent material and time which give soils some kind of inherent health or quality for example comparing a loamy soil to a sandy soil. A loamy soil may seen to be more healthy because it has a higher water holding capacity; or referred to as having a higher “soil capability’. Dynamic qualities affect soil quality or condition that we can manage, Rhodes proceeded to briefly highlight some of these factors and how the changing nature of soil properties determining soil health may be affected by management. Chemical and Nutritional factors Soil Acidity is a significant yield limiting factor in dryland agriculture in South Africa especially in KZN and the Eastern Cape and is starting to become a problem in irrigation areas which until recently have not been a familiar with this problem. Soil acidity initially starts off in small patches that expand if not rectified, they can often be identified as areas displaying poor growth (in severe cases not even weeds will grow); “seed vigour” and germination problems resulting from soil acidity have…

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By Conferences and Training No Comments

The Fertilizer Society of South Africa (FSSA) was founded in 1959 and restructured in 2014  when it became know as the Fertilizer Association of Southern Africa (FERTASA). Adriaan de Lange who served as Chairman of FERTASA since 2014 completed his second term of office and delivered his final chairman’s report at the 2018 FERTASA congress held on 19 April at the Premier Hotel, OR Tambo International airport. The South African economy grew by 1.3% in 2017 and exceeded the National Treasuries expectation of 1% growth. Economic activity was driven by agriculture with agricultural production increasing by 17.7% in 2017 which contributed to 0.4% of national GDP growth. Agricultural production in the summer rainfall areas was marked by good yields for most crops and high income from animal products resulting in an overall reduction in South African food inflation which decreased from 9.9% in February 2107 to 4.5% in January 2018, which is a clear indication of the strategic importance of the agricultural industry in South Africa providing affordable food and food security for a growing population. South Africa achieved a record maize yield in 2017 however the overall trend of reduced plantings continued as farmers moved to more lucrative crops and diversified their operations. The world wide surplus production of maize caused the maize price to plummet from a high in excess of R4000.00 in 2016 to below R2000.00 in 2017. The drop in the South African maize price was exacerbated by the change from import to export parity pricing which led to the enigmatic situation that farming debt in the summer grain production areas increased despite a record crop being harvested. The surplus production of maize and resultant lower prices has led to increased plantings of soybean over the past eight years with a result that soybean production also achieved a record yield in 2017. International soybean prices has tended higher recently which bodes well for the future of local soybean production provided that the processing capacity for soybeans increases and cultivars more suited to South African conditions are developed to increase the overall yield per hectare. Agricultural crop production in the winter rainfall areas has been seriously  affected by the worst drought in a hundred years in the Western Cape which is continuing; the wheat yields ranged from 2 – 3.5 tons/ha in the Swartland and very low to almost no yield in other areas. Fruit and grape production had mixed results whereby exports of fruit and wine was favoured by the weak Rand and in some cases the extreme drought conditions enhanced wine quality; however the quantity produced was severely affected. The Western Cape Dam levels are currently down to 18.95 from 26.9% in 2016 and the Western Cape has been declared a disaster area, fortunately relief measures are being implemented. Fertilizer prices and consumption Fertilizer prices have stabilized internationally and production is increasing however demand hasn’t increased which has put prices under pressure. de Lange commented that fertilizers are currently trading at production cost rather than…

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Biofertilizers, Biostimulants & Biopesticides: Definitions, Differences & Challenges

By Biostimulants, FERTILIZER PRODUCTS No Comments

Stephanie Roberts, Agronomic R&D Manager for Omnia gave a very informative presentation on the significance and market potential of biostimulants, biofertilizers and biopesticides including a detailed explanation of the definitions, differences and challenges surrounding the use of these products; especially in relation to Group 3 fertilizer registration in South Africa. There is tremendous interest in this market commercially as worldwide growth of the global stimulants market is expected to reach US$ 3.2 billion within the next five years while the humanitarian challenge increases as agriculture will be expected to feed an extra 400 million mouths in the next five years. Bioproducts can help to sustainably improve crop yields by reducing crop stress and improving nutrient use efficiency. However this segment of the industry faces challenges of perception as many of these products have been described with dubious claims and a mysterious technical story leading to them being labelled as “muck and magic” in the United Kingdom and “snake oils” in the USA. Some reasons that these perceptions have arisen: Many products such as kelps and amino acids derived from fish emulsions originated from the organic farming industry which has been associated with not always using the best science available. Many of these products were developed from industry driven R&D and not from Universities, even in Universities there is mistrust relating to these products. Problems of fake products; for example where people are selling caramel colourants and labelling them as “humic”. Unfortunately the genuine products don’t always work and cannot be guaranteed to always give a proper response. A lesson from the “American Snake Oil” industry  The original snake oils were used by Chinese immigrants who built the transcontinental railroad in the USA in the 1880’s to ease muscle pain. The Americans realized the potential and used extracts from rattlesnakes when the original snake oil ran out as an alternative, soon unscrupulous businessmen were selling mineral oil as snake oil; which led to snake oil gaining the reputation as something not to be trusted. A hundred years later it was found that Chinese water snakes did indeed carry Omega 3 fatty acids which have anti-inflammatory properties. The lesson from the snake oil industry is that the problem was not related to product but rather to the fake product. As Roberts explained that the purpose of Group 3 registration is to ensure that biostimulants and biofertilizers aren’t registered as Remedies but as fertilizers and that biopesticides remain registered as Remedies. It is most important to ensure that only proven biostimulants and biofertilizers are marketed to farmers and for the industry to validate the products being sold so that the market is not destroyed by non-regulated non proven products. The definition of Biostimulants according to the current Group 3 regulations of Act 36: “A fertilizer containing natural or synthetic substance(s) or organism(s) or maintain(s) the growth or yield of plants or the physical, chemical or biological condition (fertility) of the soil; and “soil improver” shall have the same meaning“. The major challenge facing…

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