The Sunday Mail
Last week, weather experts announced that Zimbabwe is likely to receive normal-to-below-normal rainfall in the 2015/16 summer cropping season.
Peter Gambara
What strategies can farmers adopt in preparation for such a scenario?
A below-normal season means any of three things: 1.The total rainfall that will be received will be below normal or 2. The rainfall season will start very late or end very early or 3. There might be a mid-season dry spell that will result in crops wilting beyond recovery points.
It is now increasingly clear that global warming is affecting weather patterns and seasons are becoming more and more unpredictable.
Traditionally, the rain season starts in November, continuing until April.
However, the season now starts well into December and ends before March is out.
Zimbabwe is divided into agro-ecological regions I to V.
Natural Region I gets over 1,000 mm of rainfall in a normal year, while NR II is split into two, A and B, with both receiving 750- 1,000mm per year.
However, NR II (B) is more prone to mid-season dry spells.
NR III receives 650-800mm of rainfall per year; NR IV 450-650 mm and NR V less than 450 mm.
Maize requires about 600-700 mm to reach maturity; therefore, farmers in NR I to III can safely crop maize under normal circumstances.
Farmers in NR IV and V should grow very short season crops.
Alternatively, they can resort to livestock production.
The demarcation of the Natural Regions is shown below.
— Zimbabwe map here —
There are several strategies that farmers can adopt to combat the effects of a below normal rainfall season.
Firstly, farmers should always strive to plant early to counteract the possible effects of a season that will end prematurely.
A maize crop that is irrigated or water-planted a few weeks before the onset of rains will have gained two to four weeks by the time the rains come and, therefore, has a better chance of reaching maturity than a rain-planted crop.
Those with irrigation facilities should use irrigation to enable them to prepare land if this had not been done already. More importantly, they should irrigate the crop so that it germinates.
An irrigated maize crop that has germinated well can withstand a two-week dry spell before the next water or rain, but once the rains start falling, the need for irrigation falls away.
Those without irrigation facilities, but have access to water, can also water-plant their maize crop.
This involves opening up planting holes, placing the seed and fertiliser/manure and then adding enough water per planting hole to enable the maize seed to germinate.
Farmers can soak the seed for a minimum 48 hours before planting it to aid germination.
If the moisture dries up before the seed germinates, this seed will rot and fail to germinate.
Farmers should, therefore, make sure there is enough moisture to germinate the planted seed.
They can only plant early if the land preparation was done in advance. In most cases, a number of farmers wait until the rains start to prepare land.
However, since they will be coming from a dry season, it is not possible to embark on land preparations until they have received effective rains.
The way around this is to encourage farmers to embark on what is popularly known among farmers as “winter ploughing”.
Ploughing up land between March and May should be promoted, whilst the ground is still wet, especially where it is fallow or the crop is a write-off.
Thereafter, the land starts getting dry and difficult to plough.
Draft oxen are also still strong now, but will deteriorate as the dry season drags on due to drought.
A few weeks before the anticipated rains, farmers can mark out furrows or planting holes on winter ploughed land.
When the rains do eventually fall, water will accumulate in the holes or furrows and farmers can then immediately plant their maize using that moisture.
Farmers should, however, ensure they have received enough rains to germinate a crop before planting.
Now that we are already in September, it is too late to do winter ploughing
Those with red soils can still plough up their lands using tractors, though. However, the exercise is likely to result in a lot of clods that will need to be broken up using a roller.
Loamy sandy soils are not easy to plough up at this time of the year as they tend to form a crust and farmers might need to apply some light irrigation to enable them to use a roam disc or plough.
Alternatively, small-scale farmers can also plant in planting holes that are made out on land that is not ploughed up.
But since the land will not have been ploughed up, farmers should expect a higher weed infestation and work with manageable areas.
Farmers should also be discouraged from planting late crops as much as possible.
There are obvious advantages of planting an early maize crop e.g. in October versus planting it late, say, in December or January.
Most crops require a certain number of heat units, which units are derived from the heat generated by the sun.
The higher the temperatures, the higher the heat units will be and the faster the crop grows.
Since we are in the southern hemisphere, the longest day is December 22 and on that day, the sun is directly above the Tropic of Capricorn.
After that day, the sun starts moving back to the equator on its way to the Tropic of Cancer in the northern hemisphere and the heat units start decreasing from that date.
Farmers should, therefore, be discouraged from planting maize after December 22.
It is even more “criminal” to plant in January!
In addition, farmers should be discouraged from growing long season maize varieties in a drought year.
A long season variety of maize will require about 150 days to maturity (DTM) whilst a medium season variety requires about 140 days to maturity and a short season variety, 132 DTM.
Hence, a long season maize variety that is planted mid-October will only mature in mid-March, whereas if the same variety was planted mid-November, it would only mature mid-April as shown below. By that time, it is likely that the rains might have already stopped, thereby compromising the maturity of that crop.
— Table here —
Farmers should prepare land where it is possible; buy their seed, fertilisers and chemicals on time so that they are able to plant early or with the first rains.
Those with irrigation or access to water should consider planting a few weeks earlier than the onset of rains.
Consideration should also be given to short season varieties as much as possible and farmers should resist the temptation to plant maize late as it risks failing to reach maturity if the season is short.
