Get the most out of your maize this season
Date: 17 September 2015
Even though weather plays a huge role in determining crop performance, growers should focus on those factors they can influence. These include, but are not limited to:
Once the maize paddock has been selected, hybrid selection is one of the most critical decisions a grower can make before planting. While selecting a full-season hybrid will usually maximise yield, also consider the ideal time for pasture or winter crop establishment, following the maize. Select hybrids that have performed consistently over a number of seasons and locations in environments similar to yours. Also consider a hybrid that possesses the best agronomic trait ratings for the conditions around the selected paddocks, e.g. disease resistance, drought tolerance and stalk and root strength.
Planting date plays an important role for achieving maximum yields. There is no single "best planting date" as this varies from area to area and season to season. The key to choosing an ideal planting date involves determining the right combination of soil moisture and temperature rather than relying on calendar dates.
Soil moisture and temperature
Uniform seedling emergence is a pre-requisite to maximising yields. To achieve uniform and optimum emergence rates planting should occur when soil temperature is 10°C and rising and there is adequate moisture at seeding depth.
Lower soil moisture and temperatures result in uneven emergence. Plants that emerge later usually get overshadowed by their neighbours and become runts, yielding much less. Planting when soils are too wet could cause soil compaction which also negatively influences plant establishment, resulting in either failed emergence, leafing out underground (leaf appearance prior to seedling emergence), smaller roots and runts.
Planting in high residue conditions
Well-drained, low-residue soils usually warm up faster, allowing for more rapid emergence and seedling growth. Planting in high residue conditions, particularly if soils are cool and wet, could potentially increase the risk of plant loss. Seedlings are weaker and slower to develop and this lengthens the duration the seed and seedlings are exposed to pests and diseases. High residue conditions can also result in planting challenges and nitrogen tie-up during the decomposition process. To minimise the detrimental effects of residue in the row, consider planter mounted devices that will cut and move residue to clear a path in front of the planting units.
A depth of 4 - 5 cm (1.5" - 2") is usually the optimum recommended depth to allow for uniform emergence and proper root development, though deeper planting may be ideal in drier soils. Planting deeper than 7.5 cm (3") can result in slower and more variable emergence, increased vulnerability to soil crusting, seedling diseases and insects, particularly in heavier and/or cooler soils. If moisture is adequate for germination there is no need to plant deeper than necessary. In contrast, planting too shallow would prevent proper development of nodal roots which are key in supplying the bulk of plant nutrient and water requirements.
Seeding rates largely depend on paddock yield potential, environment, soil fertility, moisture and hybrid choice. Typical optimal established plant populations generally range from 95,000 to 110,000 per ha with higher densities usually applied in highly productive environments, cooler climates and shorter season hybrids. Seeding rates for grain crops are usually about 10% lower. To achieve the required seeding rates, plant loss rates have to be considered. For instance, if planting in cooler or less ideal soil conditions, the rule of thumb is to plant 4 - 5% higher than the recommended rates.
The secret to growing maize successfully is getting it right at every step from paddock selection through to harvest. If you overlook any process along the way the yields will not be anywhere near as good as they could be. While maize is generally an easy crop to grow, mistakes made during crop establishment are usually irreversible, and can significantly reduce the yield potential before the plants have even emerged.