Introduction
Groundnut (Arachis hypogaea L.) also known as peanut, is cultivated in the semi-arid tropical and subtropical regions of nearly 100 countries in six continents between 40˚ N and S of the equator. It is an important legume grown and consumed globally and in sub-Saharan African countries (Okello et al., 2010a). For people in many developing countries, groundnuts are the principal source of digestible protein (25 - 34%), cooking oil (44 - 56%), and vitamins.
As a legume, groundnuts improve soil fertility by fixing nitrogen and thereby increase the productivity of other crops in the semi-arid cereal cropping systems. Groundnut requires little input, making it appropriate for cultivation in low input agriculture by smallholding farmers. Groundnuts are grown in most of SSA by smallholder farmers as subsistence crops under rain-fed conditions. Yields per hectare are generally low compared to those from developed countries like the USA, because of a combination of factors such as unreliable rains, mostly non-irrigated cultures, traditional small-scale farming with little mechanization, outbreaks of pest infestations and diseases, the use of low-yielding seed varieties, increased and/or continued cultivation on marginal land, poor adoption of agronomic practices and limited extension services. Therefore, there is excellent potential for yield improvement.
Soils
All soils, other than very heavy ones are suitable for growing groundnut, but the best are deep, well-drained sandy, sandy loam or loamy sand soils. The latter facilitates the forcing of the developing fruit into the soil (pegging). Groundnut will not grow well or fix nitrogen in acidic or infertile soils. Groundnuts grow best on soils limed to a pH of 5.5 to 6.8, provided other essential elements are in balance and available to the plant. If the pH is not optimal, certain elements become unavailable.
Fertiliser Requirements
Even though, Groundnuts respond better to residual fertility than to direct fertilization. A soil test by Demeter Ghana Limited is the best way to determine whether fertilizer or lime is required in groundnut growing. Demeter soil tests across the country have saved farmers awful lots of money by providing the farmer with the right fertilizers to apply for balanced nutrition. Liming is necessary only when the soil pH is below 5.5. However, if soil test results are not available, the blanket fertilizer recommendation is NPK kg /ha: 25 kg of N – 50-80 kg of P2O5 – 30-40 kg of K2O for the target yield of 1.2-2tons/ha. Substantial evidence exists to show that groundnuts respond well to additional fertiliser applications, even though in rural situations this is not imperative.
Being a leguminous crop, groundnuts can fix atmospheric nitrogen (N) with the aid of root bacteria. Demeter Ghana provides the best inoculants for your groundnut which boast of over 25% yield increase. For this reason, a well-inoculated crop with Rizoliq Top inoculant does not depend on nitrogen fertilisation. Root nodules, which fix nitrogen effectively, have a pinkish appearance when dissected. It is also a known fact that Groundnuts with effective root bacteria do not need additional nitrogen.
Nitrogen (N)
Groundnut as earlier discussed are legumes and fixes atmospheric nitrogen with the help of Rhizobium in the root nodules. This process is highly improved with Rizoliq Top (Groundnut/Cowpea) inoculation from Demeter. This helps to partially fulfil its nitrogen requirements. However, it takes a few days to develop root nodules. Therefore, some available nitrogen is required in the early stages of plant growth. Mostly, soil test results indicate most soils have optimal N levels to support this stage of growth across the country. However, without soil analysis, a blanket recommendation of 10-20kg/ha as Ammonium sulphate at land preparation or sowing is recommended for soils with medium to low nitrogen content (this classification is usually.
Phosphorus (P)
The requirement for phosphorus in nodulating legumes is higher compared with non-nodulating crops. If soil phosphorus is less than 15kg/ha, there is a need to apply phosphatic fertilizer. Single Super Phosphate is recommended because it contains phosphorus, calcium and Sulphur which are required by groundnut. In soils with optional P levels, which is mostly the case, A recommended 200-255kg/ha of Polysulphate is the super product for yields above 3 tons/ha.
Potassium (K)
Like other crops, groundnuts require adequate levels of potassium for normal growth and development. But an oversupply of potassium in the soil can induce a calcium deficiency, which is reflected in a lower yield and quality. A potassium application may not be required unless there is less than 100kg/ha available in the soil. However, the super Polysulphate application caters for the K application. Farmers continue to save money and increase yields using Polysulphate.
Calcium (Ca)
Calcium (Ca) is very important for seed development (pod filling stage) and is regarded as an essential element in groundnut production. Calcium is taken up directly by the developing pods from the top 5-7cm of soil. Groundnuts are particularly susceptible to a calcium deficiency in the soil. Where a crop is grown on calcium deficient soils, the producer will have a direct seed loss as well as indirect damage to the seed, which is not always visible. Seed produced under such conditions is not suitable for planting. Seedlings are often misshapen with low vigour and the heart or embryonic axis is usually damaged to such an extent that no germination takes place. Since groundnut will not grow in acid soils and liming may be necessary for such soils for good production, the Demeter Granulated Calcium Carbonate is a recommended product. In situations where less than 100 mg/kg of Ca is present in the soil, calcium application is required and the basal application of Polysulphate does the magic.
Sulphur (S)
Sulphur helps in biological oxidation and reduction processes and chlorophyll formation. Acid soils are often deficient in Sulphur. In soils where available Sulphur is less than 10ppm, the Sulphur application is necessary. However, additional Sulphur is not required after Polysulphate application.
Iron (Fe)
Groundnut growing in soils with high pH often shows iron chlorosis. Spraying Iron-based foliar are a substitute, However, Polysulphate mitigates high pH making the iron available for crops to assimilate. This is among many other reasons why the Polysulphate is a Super product.
Zinc (Zn)
Zinc increases the chlorophyll content in the leaves, the number of nodules and pod yield. Zinc deficiency occurs when the soil is alkaline or low in organic matter, under high levels of soil P or when soils are cool and wet during the vegetative phase. Manure or Polysulphate application prevents this deficiency for higher and good quality nuts.
Potential Problems
Groundnut is an important cash crop for domestic markets as well as for foreign trade in several developing and developed countries. However, its production is constrained by Aspergillus species, which cause quantitative losses and produce highly toxic and carcinogenic chemical substances known as aflatoxins.
Although groundnut has a huge potential as a cash crop to improve the livelihoods of farmers and traders in various parts of Ghana, its market is declining, and the export of the crop has come to a standstill. This is due to aflatoxin contamination of the crop and the difficulty of meeting tolerance limits by importers and food processors, leading to the rejection of the crop and a reduction in market demand. Aflatoxin contamination is both a pre-harvest and post-harvest problem. Therefore, the management of aflatoxin contamination of groundnut in Ghana is very important by using cultural practices such as habitat management, soil amendments and pre-and post-harvest management, using physical control methods, using biological control methods, using resistance groundnut varieties and using chemical control methods.
Conclusion
In summary, a well-nourished and properly maintained plant is more healthy and less susceptible to pests and diseases. Leading to high yield and quality nuts.
