By Albert Makendenge
Groundnuts, which are grown for both commercial and domestic purposes, are right up there with some of the most celebrated crops in the leguminous family. Below is a production guideline of the crop, from planting right through to harvesting.
Groundnut is a summer crop that is very sensitive to low temperatures, requires high temperatures (18 to 30oC) and a frost free period of about 160 days for the best germination and vegetative growth. Evenly distributed of rainfall in the region of 500 to 700 mm per annum will be satisfactory for a good yields of groundnuts. A great deal of moisture is needed before flowering and during pod filling (moderate during flowering and no water or rain during ripening)
Groundnuts grow best in well drained, red-colored, yellow-red, fertile, sandy to sandy loam soils with a pH range of 5.5 to 7.0. Low salt tolerance and long tap roots (up to 2m) make shallow, compacted and saline clay soils unsuitable for groundnuts.
Seedbeds should be prepared either on flat or widely ridged fields. For successful groundnut production, deep ploughing should be implemented. A uniform field with sufficient planting depth and spacing, good germination, weed control and sufficient moisture retention is imperative for good yields.
Early planting, as soon as the rains come in mid-October to mid-November is recommended as late planting leads to lower yields. Planting depths of 5 to 7.5 cm are preferred and the best spacing under rain-fed conditions should be 90 cm with a spacing of 4 to 7 cm between the plants; and 30 to 35 cm under irrigation.
Compound C (5:15:12) at a rate of 250kg per hectare or alternatively Compound L (4:17:11). Compound D (7:14:7) can also be used if these two cannot be found. 8 to 12 weeks after planting, Calcium Sulphate or Gypsum should be applied at a rate of 560kg per hectare. Nitrogen fixation in legumes depends on the formation of nodules by rhizobia, which is why the seeds should be inoculated either through coating the seed with the bacteria or by treating the soil with a granular or liquid inoculant.
In areas limited soil moisture where irrigation is practiced, avoid application of excess moisture by ensuring that scheduled irrigation is practiced. The irrigation method will depend on available water resources and the available irrigation equipment.
An integrated weed management which comprises mechanical, chemical, cultural and biological weed control methods should be implemented since groundnuts are susceptible to a wide range of weeds that compete for moisture, nutrients, light and space and thus resulting in lower yields. Three mechanical weeding operations are important with the first one coming prior to the emergence of seedlings (seven days after planting). The second one will be performed at 21 to 28 days after planting with the last one depends on weed growth and should not be delayed later than 60 days after planting.
Pest and Disease Control
Leaf spot and stem remain the most prevalent diseases and are particularly devastating when the weather is warm and the soil is moist. Common pests include cutworms and aphids. Besides the use of chemicals, cultural rotational methods can also be used to disrupt disease and pest cycles and to ensure the efficient use of nutrients.
Harvesting, which is determined by the prevailing weather conditions, can either go by way of mechanical methods through the use of a digger that lifts the groundnuts and detach them from the soil or manual methods. Maturity days differ from variety to variety with early maturing groundnuts like SC Mwenje and SC Nyanda taking about 115 days or less and late maturing varieties taking about 160 days to mature. Signs that the crop has matured include darkening of the pods, seed color changes from white to pink and dull pink as well as the development of a yellow color on the leaves.