In this post, we present important guidelines that will help yam farmers improve yam production.

Yam is a very valuable and very important commodity in Nigeria. In some societies in the country, festivals are staged to mark the beginning of yam harvest while some use the tuber crop in fertility and marriage ceremonies.

Yam is cultivated on 3 million hectares of land in Nigeria. The country alone produces 36 million tonnes annually, accounting for 68% of global production.

This makes Nigeria the world’s largest producer of yam.

In order to further improve these numbers, Dr Edward Ngozi Nwaogu, Head of Station, National Root Crops Research Institute, Abuja presented to farmers important factors they need to consider before and after planting yam.

How to improve yam production

Site selection:

Yam grows well on upland soils. Being a high nutrient demanding crop, yam requires soil that is deep, free-draining, and relatively high to medium in fertility with loamy sand or clay loam characteristics. Good soil drainage is essential for optimum yields of the crop. Heavy clay soil tends to water-log in the rainy season and is liable to cause tuber rot. Infertile soil is not recommended for yam production because it will be unable to retain sufficient water or nutrients to produce reasonably-sized tubers. Also, soils with high amounts of gravel or stones are unsuitable as they constitute a barrier to tuber penetration and root anchorage.

Land preparation

For optimum yield performance, planting is usually done on mounds or ridges. The size (height) of the mounds varies from 30 cm to as high as 100 cm depending on yam variety, locality, targeted tuber size and culture. However, planting yams on ridges instead of on mounds offers a greater opportunity for increased seed rate and ensures optimum utilization of land resources for sustainable tuber production. In most traditional farming systems in Nigeria, yam is planted on flat land. This practice is common among people from Abia, Edo and Delta. In such systems, holes are made in rows and yam seeds are planted without the soil being heaped on top.

Planting

Yam can be propagated as ware yam or as mini-sett, depending on the objective of the planting and size of seed yam tuber required. In Nigeria, farmer-saved seeds are the predominant source of planting material. For the production of reasonably large tubers, large ware tubers of about 2 -3 kg are cut into smaller sett sizes, ranging from 300g to about 600 g. These setts are then planted to produce normal seed yam tubers weighing one kilogram and above. This method substantially reduces the number of tubers that could be used for food because when seed-sized tubers are in short supply, larger tubers are converted to seed yam by being cut into setts. Cut yam setts of about 20 – 50 g size can be used to produce seed yam tubers using the yam mini sett technology introduced by NRCRI Umudike and IITA. In cutting yam into plantable seed setts, care should be taken to ensure that the cut sett possesses a substantial amount of the peel from which sprouting can occur.

Yam is planted at a recommended distance of 1 m x 1 m for (ware yam production) while a closer intra-row spacing of about 20 – 40 cm is required for smaller setts. Yam planting is done by placing the skin of the cut sett in close contact with the soil and covering it with soil. For dry season planting, mulching with dry grasses to conserve soil moisture and protect the sett from harsh sunlight and heat is very important.

Field Maintenance

For a sustainable yield of yam, timely routine maintenance of the yam field is important. Operations such as weeding, staking, fertilization, earthing up and erosion control should be embarked upon and on time too. These operations have a critical influence on yam tuber response and the ability of the crop to assess essential growth nutrients from the soil. Best yields are obtained when weeding is done as frequently as they grow up in the yam plot. Fertilization is best done 8- 10 weeks after planting. Fertilizer application is by banding. For low fertility classed soils, 400-500 kg/ha of inorganic NPK 20:10:10 fertilizer is regarded as adequate for optimum yield of yam. However, the complementary application of inorganic NPK fertilizers with organic manures such as poultry dropping and animal waste enhances fertilizer use efficiency of the crop and maximizes tuber yield response.

Harvesting

Maturity in yam is attained after 6 – 12 months of growth of the crop. At maturity, the leaves turn pale yellow and gradually dry up. This is quickly followed by dryness of the yam vines. Harvesting can be either double or single harvesting. Single harvesting is done by harvesting the matured yam tubers whole i.e. without leaving any part thereof inside the soil. Double harvesting is done by carefully removing newly formed tubers from the “corm region” while leaving the roots intact to form another tuber in place.

Storage

After harvesting, it is best to allow the yam tubers under shade for 2 – 3 days for curing to take place. Curing refers to a situation where the tubers are placed in a condition that allows the heat and water generated during harvesting to dry up on the surfaces of the tubers in order to initiate the process of healing. Proper storage of yam is an essential step in yam production. Improper storage causes tuber rot and dehydration and thus resulting in post-harvest losses.

A good storage facility must allow proper circulation of air within the environment where the tubers are stored. It must protect the tubers from direct contact with rain or sunlight capable of facilitating microbial breakdown of the tubers. It must also be cool and free from materials likely to introduce degrading micro-organisms. Lastly, it must be large enough to adequately contain the volume of tubers to be stored.

Source: dailytrust