Most agroforestry beginners often find themselves in a fix when it comes to establishment of tree farms.
The big question normally is: Should I buy seedlings from established nurseries or should I prepare my own? Which one is more economical?
I have bought ready seedlings and I have also prepared my own nurseries from seeds purchased at the Kenya Forestry Research Institute (Kefri).
In my experience, each has its own advantages and disadvantages. Buying ready seedlings will save you time and effort but it is more costly.
Having your own nursery is much more economical on the money front but you have to invest a bit more time and effort in it.
Consider this: Suppose you have a five-acre farm to plant acacia trees. With the ideal spacing of five metres, you need 2,500 seedlings. At an average cost of Sh50 for each, it will cost you Sh125,000 on seedlings alone.
Now, if you were to make your own seed bed, you would need a quarter a kilo of seeds (at Sh800) that will give you the 2,500 seedlings.
Even with additional costs of pots (sockets), fertiliser, water and labour, you will spend less than a third of Sh125,000.
However, it requires a lot more investment in time and effort. For starters, your timing has to be perfect for the seedlings to be ready for planting in the rainy season.
If you want to plant at the onset of the April long rains for example, sow your seeds in December. If you want to plant in the October-November short rains, sow by latest June.
Additionally, knowledge on pre-sowing preparation is key. Different types of seeds lend themselves to different preparations. If you get it wrong, you will be hit by costly setbacks to your project.
Seeds like those of acacia xanthophloea, for example, need to be soaked in hot water for 12 hours. Others, like the Meru Oak, are soaked in cold water for a similar period.
Why do you need to soak the seeds?
According to the Seed Handbook of Kenya (2nd edition) edited by Omondi, W, Maua, JO, and Gachathi, FN, it mimics the conditions under which the seeds germinate in their natural ecological zones.
SOAKING PERIOD HAS TO BE RIGHT
Many acacias, for example, grow in hot semi-arid regions, while the Meru Oak grows in wet zones.
Over the years, the seeds have developed defences to survive these conditions.
These defences include hard coats and germination inhibitors that can only be softened or removed under induced conditions.
Soaking before planting therefore helps break down the seed’s natural defences against what it expects from nature, which then allows it to germinate faster.
In the wild, a seed can expect to encounter harsh heat and cold, very wet or dry conditions.
Nature gives seeds an internal gauge to help them know when they should grow.
Michael Meso, a Kefri seed scientist, says moisture levels play a big role in alerting seeds to optimal growth times.
By soaking the seeds, you quickly boost the moisture content around them, which signals that it is now safe to grow.
Seed germination inhibitors are designed to prevent them from germinating inside the fruit. These inhibitors must be leached away before a seed can germinate. In nature, this process can take a long time. But when you soak your seeds, the process is shortened.
Germination of seeds like acacia is also speeded up after spending sometime in an animal’s gut. Animals like elephants and giraffes eat the seeds and they germinate after they are expelled in their dung. Acids in the animals’ guts corrode and weaken the seed coats so they take in moisture when they are expelled.
But the soaking period has to be right, otherwise you will end up either cooking or drowning them.
The recommended soaking time for seeds is 12 to 24 hours and no more than 48 hours. For those that are soaked in hot water, the container for boiling water and the one for soaking should be different.
After soaking your seeds, they should be planted in well-prepared beds that contain sandy soil and covered with dry grass mulch, which is removed immediately germination starts.
Each seed type has its own germination period. Acacia seeds, for example, germinate within seven to 14 days while those of Meru Oak do so within 15-30 days.