Soyabeans, benefits and the simple science behind crop rotation

My grandmother used to tell me that I am not supposed to plant the same crop on the same land consecutively.

And when I asked her why not? Her reply would be it was not right. Well, that is where her understanding ended, but all she was telling me was to rotate crops to fight pests for more yields. Now, let’s explore the benefits, rules and the science behind crop rotation.

Why Rotate
The first rule is that crops of the same family should never be planted following each other because they share the same pests and diseases. At the time of growing the first crop, there will be pest and diseases that will build up. Therefore, by the time you plant the second crop of the same family, the diseases and pest will be ready to attack it.

Weeds in most cases are not beneficial to the crop since they act as alternate hosts of both pests and diseases. This is apart from competing with crops for nutrients, space, sunlight and water.

The second rule is that in the sequence, there needs to be a legume. Leguminous crops e.g soya beans. The advantage of having soya beans in the sequence is that it fixes the atmospheric nitrogen into the soil through a process known as biological nitrogen fixation with the help of microorganisms found in their roots known as rhizobia. This means the atmospheric nitrogen, which is in its molecular form N2 is converted to ammonia (NH3).

The ammonia is then converted into ammonium (NH4+) which is the form that is utilised by the plant. After soya beans are harvested, the amino acids in the crop are realised back into the soil where they are converted into nitrate (NO3-), which is a form that is utilised by plants. You can rotate a cereal such as wheat with soya beans.

Furthermore, legumes are also called green manure. This is because of their ability to biologically fix nitrogen into the soil. For you to get the maximum out of green manure, you need to incorporate the legume into the soil. Green manure also has the advantage of improving the soil structure and the water-holding capacity of the soil.

The third rule of crop rotation is to rotate crops with different rooting depth. The deep-rooted crop should be rotated with the shallow-rooted. For example, sunflower (deep-rooted) should rotate with wheat (shallow-rooted).

Crop rotation keeps the farmer in production throughout the year. Although the planting seasons are determined by the amount of rainfall, a farmer should take advantage of this using a rotational sequence.

Crop rotation further helps to reduce the amount of fertiliser used, especially if you incorporate legumes, thus cutting the cost of production and increasing the profit margins.

Though not proven, there is an increase in yields in a rotation sequence, which some agronomists term as the rotational effect. The growing of the different crops on the same piece of land in the same season also cushions the farmer from losses.

Crop rotation encourages the utilisation of various crop species, it assists in the buildup of soil organic matter, improves soil structure and the chemical and biological soil environment. Soil organic matter has additional advantage of improving water infiltration and retention, increased droughttolerance and decreased soil erosion.

The main disadvantage of crop rotation is that the types of the crops chosen depends on the farmer’s preference, which is influenced by the environment especially water availability and temperatures.

Income generation
Soya can become staple food in Kenya. It’s possible for each rural household with a piece of land to plant on at least ¼ acre and produce 100 kg of beans needed for annually consumption of five people. The requirements are few: only 5kg of seeds, a 1/ 4 acre of land, the family members will provide manual labour for production and preparation.

Ordinary tools and materials readily available in the will work. The total investment needed to allow a single household to produce the quantity of soya beans to feed them for a year is about KSH 1600 per annum.

Soya bean production is an income generation activity. By investing less than KSH 8,400, a farmer can generate a profit of KSH 84,0O0 on one acre of land annually. A farmer will need only 25 kg of seeds, one acre of land, some tools and manpower. You can generate more income with soya bean production than maize, cassava or bean production!

At home you can use soya food products in a huge variety of recipes. You can prepare soya foods from home grown soya beans or buy them at a local market. A family of five will need 100 kg soya bean grains annually. A price of one kilo of soya bean grains is less than KSH 84. Two kilos of soya bean grains per week is enough to provide nutrition to a family of five.

With less than KSH 840,000 you can build and operate a small scale unit to produce soy food: soy milk, tofu, soy flour, etc. and generate at least KSH 84,000 every month.That’s pretty incredible!

You can buy and sell soya products in a retail shops. There are also restaurant opportunities being created through this industry. Opening a restaurant in your city – you can invest less than KSH 168,000 and make a monthly profits of KSH 42,000.

Agro-processing
Soybeans are grown for their oil and meal. Soybeans are crushed, the oil is extracted and the by-product is high-protein soybean meal. The oil has many uses including as an edible vegetable oil. The meal is used as a source of protein in animal feed and primarily included in feed for poultry and fish. Less is used for beef, dairy, sheep or goats.

Seeds
So the key is to select varieties that are adapted to your day length, soil type and weather environment (rainy or dry or irrigated). KARLO have done a great job of breeding and selecting adapted and high-yielding varieties. In Kenya you don’t have too many choices for seed. Seedco have also developed another variety which is adaptive to Kenya. Having the right variety of good quality seeds will make all the difference on whether your venture is successful or not.