The Sunday Mail
Agriculture
Peter Gambara
Most high rainfall areas in the country received rains almost every day during the month of December, leaving very little time for farmers to do land preparations and plantings.
As we are now past Christmas and approaching the New Year, many farmers are still to plant their targeted hectarage as the planting window slowly closes.
The worst affected farmers are those with heavy red soils as they tend to drain slowly, making it difficult to work the soils some two to three days after a downpour.
The question, therefore, in most farmers’ minds is: Should they continue to plant after Christmas and New Year or not?
Traditionally, our summer season starts around mid-November, but of late, we have seen reliable rains only arriving in December.
This has been attributed to climate change.
However, this tends to limit the time available for farmers to prepare their land and plant.
To answer the crucial question, it is important that I go back to some geography that we were taught in high school.
Since Zimbabwe lies in the southern hemisphere, our longest day is December 22, when the sun is directly above the Tropic of Capricon.
After that day, the sun starts moving back to the equator on its way to the Tropic of Cancer in the northern hemisphere.
The shorter the days, the lower the heat units that are available to our crops and, therefore, after December 22, the heat units start decreasing as the sun moves away from the southern hemisphere.
December 22 is, therefore, ideally the last planting date for most summer crops in the southern hemisphere.
Any crop that is planted after that day should be considered to be a late crop and risks not getting enough heat units to reach maturity or achieve a good yield.
Farmers should know that a long-season maize variety requires about 150 days to reach maturity, while a medium-season variety requires about 140 days.
A short-season variety needs 132 days to reach maturity.
It is, therefore, risky to plant a long-season variety late, as it might not be able to reach maturity.
In recent years, the rainy season has tended to end prematurely before some crops have matured.
Using the Seed Co nomenclature that most farmers are aware of, the 7-series (SC 727 or SC 719) should ideally have been planted by end of November, while the 6 series (SC 649, SC 635 etc) should ideally have been planted by mid-December.
Those planting late should consider using the 5-series (SC 529, SC 555, SC 513 et cetera).
However, many farmers who are contracted to the CBZ Agro-Yield scheme found themselves in a difficult position as they failed to secure the necessary basal fertilisers on time, while they had already chosen long-season varieties.
Such farmers tend to continue planting the long-season varieties, even this late.
This should be discouraged.
While some farmers continue planting maize after the New Year, this is not recommended as the yield loss due to late planting is high.
Research has shown that delays in planting a crop can contribute 0,3 percent to 1 percent of yield loss for each day that the planting is delayed.
A farmer planting a long-season variety like SC 727 with a potential yield of 16 tonnes per hectare (ha) will experience a yield loss of approximately 50kg per day for each day (16 000kgs x 0,3 percent = 48kg/day/ha).
Bear in mind that the more the delay, the higher is the yield loss per day; hence a scale of 0,3 percent to 1 percent.
At 1 percent, that loss increases to 160 kg/day.
Therefore, a farmer planting SC 727 between now and the New Year stands to lose 1,5 to 4,8 tonnes/ha maize yield potential.
As discussed last week, late-planted maize tends to be attacked more by fall armyworm than an earlier planted crop.
The December and January planted crops tend to be highly susceptible.
It is much more difficult to control weeds this late into the season as the rains tend to germinate the entire weed spectrum in the ground by this time of the year.
By this time of the season, the weeds also tend to be much more intense, covering every space of ground and can be very difficult to control.
Most herbicides are only effective during the early leaf stages of the weeds.
Farmers who wish to grow winter wheat should pay attention to when they are likely to harvest their crops.
The more summer plantings are pushed late into the season, the more this is likely to affect subsequent winter wheat plantings.
It eventually becomes a vicious circle, as a late planted winter wheat crop is likely to be affected by November rains and also delay the next summer crops.
Having discouraged farmers from planting maize late into December and January, farmers will then want to know what other crops they can still grow in January.
Some farmers tend to grow soyabean up to the first week of January and get away with it.
Soyabean reach maturity earlier than maize and therefore farmers can still afford to plant it late and still harvest in time for winter wheat.
Sorghum is another cereal crop with fertiliser and chemical requirement similar to maize and, therefore, those farmers who fail to plant maize on time can still use the same inputs to grow sorghum.
Sugar beans can be grown in January as the crop matures in three months.
Therefore, a crop planted in January can still mature by April.
Some farmers grow sugar beans as a filler crop where maize could not be planted for whatever reason, or where the main crop has failed or where a farmer harvests an early planted crop like green mealies.
Sweet potatoes are another crop that farmers easily establish between January and February after they have finished establishing the main crops.
While sweet potatoes were previously grown mainly by small-scale farmers, A2 farmers can also grow the crop better than the small-scale farmers as they can apply basal fertilisers to the crop, unlike the small-scale farmers, who do not apply any fertilisers.
The demand for sweet potatoes has increased considerably over the years.
If a farmer has to plant crops late into the summer season, consideration should be paid to the choice of variety, pest and weed control, potential yield loss as well as establishing subsequent winter wheat plantings.
Wishing you a Happy New Year.
Peter Gambara is an agricultural consultant.
