Expert tips to get the most from irrigated wheat

Irrigated wheat is grown by many South African grain farmers in rotation with summer grains such as maize and soya bean. André du Toit, a senior wheat breeder with Pannar Seed SA, shares his knowledge and experience on how farmers can maximise the productivity, and therefore profitability, of these wheat crops.

With the wide range of wheat cultivars now available to South African farmers, it can be bewildering to select and grow seed that is best suited for a particular farming business’s production conditions and goals.

Fortunately for wheat farmers, experts such as André du Toit, senior wheat breeder with Pannar SA, are keen to offer guidance on cultivar selection and production management.

Du Toit says important factors that wheat growers should consider in their selection of appropriate cultivars include the number of days from planting to flowering; plant height at harvesting; stem standability as the plants and their grain mature; tolerance to pre-harvest sprouting; and tolerance to stripe rust, leaf rust, stem rust, white rust and fusarium head blight.

From the old to the new
An attractive aspect of Pannar’s many modern wheat cultivars is, for example, that they require lower seeding rates to achieve the same, or even greater, grain yields than older cultivars, says Du Toit.

Some of the company’s latest cultivars can be planted at 75kg of seed per hectare for early plantings in June, and at up to 110kg/ha for later plantings in July. This typically results in a germination density of 175 to 250 plants/m2.

“Until as recently as two years ago, most of South Africa’s wheat seed companies and growers aimed to achieve germination of at least 250 plants/m2. However, about 15 years ago, Pannar began research to develop irrigated wheat cultivars based on dryland wheat production principles that required significantly lower seeding rates.

“We wanted to find and breed irrigated wheat germplasm that is better adapted to local production conditions, and so can be planted at lower seeding rates but still have high yield potential,” Du Toit explains.

The present-day results of this research are commercially available irrigated wheat seed cultivars that, once planted and germinated, quickly go into a stooling phase, where the number of tillers produced by each primary wheat plant is greater than that of older cultivars.

In older wheat cultivars where targeted germination density was at least 250 plants/ m2, this would not leave enough space for the increased tillering desired as heatwaves and cold snaps.

And compared with the higher wheat plant populations of the past, today’s lower plant population, to a large extent, also inhibits the prolificacy of fungal pathogens due to the unattractive microclimate for them between the less densely spaced plants.

“These increased spaces also allow the wheat plants better access to sunlight for photosynthesis that is so important for the production of the grain that farmers want to harvest,” continues Du Toit.

Spread flowering
He explains that a wheat plant typically flowers over a period of five to seven days, starting with the primary ear, followed respectively by the secondary, tertiary and subsequent ears.

If during this period a cold snap lasting one to two days arrives, these temperatures will negatively affect only some of the ears that are in different stages of sensitivity to the cold.

So instead of losing their entire harvest, farmers are likely to lose only 10% to 20% of the crop’s yield potential and therefore will probably still make a profit. This risk can be reduced even further by planting two modern wheat cultivars together, each with a slightly different flowering time.

Du Toit and his colleagues have found that many of South Africa’s wheat farmers still tend to over-fertilise their crops to try to boost yields, despite growing the latest cultivars. For example, trying to achieve a grain yield of at least 8t/ha, they apply 200kg/ha or more of nitrogen.

“When I’m asked for fertilisation advice, I tell wheat farmers that it’s not the volume of fertiliser that’s most important for maximised wheat yield, but rather the distribution of this fertiliser over the crop’s lifespan. So instead of applying a wheat crop’s total fertiliser requirement over three applications, rather apply it over six applications. This has been found, on average, to noticeably increase wheat grain yields,” Du Toit says.

Another valuable source of information to guide a wheat farmer’s choice of cultivars is
data generated from the Agricultural Research Council’s independent field trials.

These are typically conducted at various locations around the country to maximise the accuracy of the results. And the trials are also spaced over at least three consecutive wheat production seasons.

Du Toit recommends that farmers use this freely available information to decide on wheat cultivars that are most suited to a particular farm’s production conditions and goals.

“A wheat farmer should ideally select cultivars that consistently show desirable performance traits for a particular area over multiple growth classes and seasons. The
selected wheat cultivars should also show consistency in these desirable traits in both higher potential and lower potential production areas.

“Ultimately, the farmer must calculate the input costs versus the potential yields for each wheat cultivar being considered, and select only those that generate appropriate returns on investment,” he adds.

Sound management maximises yield potential
Once having settled on the cultivars of choice, a wheat farmer must, as far as possible, create and maintain the optimal conditions needed for the cultivars to achieve their full yield potential on the particular farm.

Du Toit offers these tips for farmers aiming to improve their management and cut out mistakes:

  • Know your production environment well and manage your crop accordingly;
  • Implement crop rotation in your soils to break pest and disease cycles;
  • Manage your irrigation water effectively; keep your groundwater at field water capacity at all times so that the wheat plants are never under- or over-irrigated from planting to the start of the drying-off period, and so that you do not waste water;
  • Have your soil fertility tested before planting and properly address any resultant recommendations before putting your wheat seed into the soil;
  • Buy only good-quality seed from trusted suppliers so that you achieve even and maximum germination and emergence;
  • Plant at the correct time, at the correct seeding rate, and at the correct planting depth;
  • Plant at the correct speed;
  • Constantly monitor crop performance so that you can catch and treat any problems while they are still relatively minor;
  • Stop irrigating your crop at the correct time ahead of the intended drying-off period. When the stem between the flag leaf and the ear is visibly yellow across 50% of the whole crop, irrigation should be stopped;
  • If the land’s groundwater has been maintained at field water capacity, these reserves should be sufficient to carry the remaining 50% of the crop through to the start of the drying-off period. Continuing to irrigate at this time is wasteful and will reduce the quality of the wheat grain.

Phone André du Toit on 082 550 6019, email him at andre.dutoit@pannar.co.za, or visit pannar.com.

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