Fertilising your land

Use enough fertiliser and place it correctly, so that you can be assured of a good yield, says Bill Kerr.

Plants suffering from lack of nitrogen in the soil.
Photo: FW Archive

In the last article, we discussed marking out and digging planting holes. The next task is to place fertiliser in these holes.
Fertiliser is necessary because, when you remove grain or produce from the land, you automatically remove the nutrients from the soil that the plants have used to grow. It’s like a bank account: if you keep on withdrawing money without putting enough back into it, you’ll eventually have no money left.

Broadly speaking, there are two types of fertiliser – organic and inorganic. The inorganic kind, such as basal fertiliser in the planting hole with LAN (limestone ammonium nitrate) as a top dressing, is increasingly used by small-scale farmers and produces good short-term results. However, these fertilisers are expensive and can damage the soil over a long period.  

Organic fertilisers such as manure and compost are cheaper and more sustainable options. They can achieve similar yields to the inorganic fertilisers if used properly. A method for making good quality compost will be described later in this series. For now, let’s assume that you’re using basal and LAN.

Quantities
Whatever fertiliser you use, the principle remains the same: the quantity you put down should be enough to replace the nutrients that will be removed by the yield you expect to harvest.

Figure 1 is a general guideline: levels of fertilisation will vary according to the state of the soil and the standard of management. But whatever you do, put enough fertiliser on a smaller plot rather than spreading it too thinly over a large area.


For example, if you have only four 50kg bags of basal fertiliser and four 50kg bags of LAN, it’s better to put all of it on 1ha at
200kg/ha rather than spread the fertiliser over 2ha at 100kg/ha. Your yield potential will still be 4t (4t/ha from 1ha or 2t/ha from 2ha). But by doing 1ha at the highest standard, you’ll have a better chance of achieving that yield.  Also, in the event of a serious drought, you’re more likely to get enough grain to feed your family. If you do 2ha at a lower standard of management, with less mulch and probably more weeds, it’s likely your crop will fail completely.

Placement
Pour the fertiliser carefully into the lowest point of the hole. Next, lay a small amount of soil over the fertiliser to prevent it from ‘burning’ the seed. If you use manure or compost, make the holes deeper (10cm to 15cm) and put 350ml (about the quantity of a cooldrink can) in each hole. If your soil is acidic, place lime in the hole first.