Maize Planting: the Key Stage

Maize Planting: the Key Stage

As maize plantings are underway, we would like to remind producers how much this stage is important for the correct harnessing of the crop’s full potential.

Planting precision and crop establishment quality are decisive factors for the crop’s development and yield level. A solid mastery of all these early-stage parameters is vital if one wants to place the crop on the right track from the outset. Covering issues going from hybrid choice to good planting practices, below is a quick review of the aspects that producers should adopt in order to harness the full potential of hybrid genetics.

Planting Date

Planting date is important for all crops and it should allow one to harness all the climate possibilities in a given region.

The planting date should be a compromise between the need to take up the most of the climate window as fast as possible, in order to allow the chosen variety to express its full potential. Thus:

• The soil should be warm, but not dry. Maize emerges when soil temperature reaches 6-8°C. Remember that soil temperature rises gradually and steadily in spring, regardless of air temperature variations.
• The soil horizons must not be dry, because seeds need moisture in order to emerge. A drying soil causes irregular emergence, which is highly detrimental to yields.
• Another important factor is the technical level of the planting practices: the number of planter sowing units or the number of planters/drills, the availability of fast planters, etc. These questions become vital when one has to plant increasingly large areas, within short favourable climate windows.

Crop Density: the Yield Basis

Yield is a direct result of the amount of sunlight captured by the canopy (leaf area index correlated with plant density) and the length of the crop’s activity (earliness = length of its growth cycle).

 Planting density is therefore based on:

1. Hybrid earliness,
2. Accessible yield potential (water supply availability),
3. Crop use (harvested for grains or as whole plants),
4. Soil type and genetic type.

Planting density = density objective at harvest + predictable losses during the crop’s growth cycle.

Therefore, one should:

• Set density based on earliness – that is, use the number of plants to compensate for the lower number of leaves in early varieties and/or for limited sunlight.
• Ensure equal competition among neighbouring plants, to prevent sterility in the dominated ones. The fertility rate (the number of ears per hundred plants) is a good physiological indicator of plant population quality. It must be above 95 percent.
• Protect the vegetative apparatus against the bioagressors that could weaken its photosynthetic ability.
• Row spacing as practiced today varies between standard distances (75-80 cm) and narrower ones (60 cm), but will have little influence on optimal plant density when the latter is based on the above criteria.

> The Response to Density Depends on Hybrid Earliness:

The later the hybrid, the more leaves it has; therefore, the number of plants per hectare needs to be smaller, in order to provide an optimal LAI and thus ensure sufficient sunlight capture.

> The Response to Density Depends on the Soil Type:

Light soils respond more strongly to density and require more plants per hectare than heavy soils, to attain the production potential. Chernozems rank in between.

With modern hybrids, even in case of moderate water stress, overdensity poses lower risks than underdensity, which prevents the hybrid from expressing its full potential. Maize has a limited ability to compensate.

Soil Preparation

Soil Preparation

The various soil preparation operations are aimed at creating a soil texture that favours rooting and emergence. Maize takes root much better in a homogeneous – even a slightly compact – soil, rather than in a hollow soil or in successive horizons of heterogeneous porosity. In order to reach that objective and regardless of the equipment or work stage (tillage or subsequent passes), the operations should be done in dry soil. Seedbed preparation (which is done early in clay soils and at the last minute in the most compact soils) must be done with a minimum number of passes. There is no such thing as an ideal seedbed preparation. More often than not, it is a compromise among the weather, the available work days, the equipment, and the size of the company. What is important above all is to make sure that the soil does not get dry between the various passes and to keep the soil sufficiently compact, in order to preserve its moisture.

Depth and Planting Quality

With maize, every plant matters. Plant population homogeneity is key to successful cultivation and it is largely determined by planting precision. The objective is to obtain fast and homogeneous emergence. To this end, the uniformity of the seeding depth is essential. The main way to ensure it is a moderate planting speed, depending on the planter technology: 5-7 km per hour for traditional modern planters, and up to 10 km per hour for the latest “fast” drills.

The seed must come into contact with moisture and also benefit from sufficient air movement, to enable germination. Thus:

–          It should be placed deep enough (≥ 4-5 cm) so that it is protected from cold, birds, and soil surface becoming dry;

–          It should not be placed too deep, either. The purpose is to limit seed reserve depletion during coleoptile elongation, reduce emergence length, and limit risks of damage by animal and plant parasites in the early stages of the crop’s development.

Depending on the soil type and the planting date, the seed should be buried at a depth of 4 and 7 cm, making sure that:

–          The soil is dry, but not dried up around the seed, and it contains enough finely textured material that favours seed-to-soil contact;

–          Clods are left mostly on the surface in compact soils, as maize has good emergence ability in cloddy or rocky soils;

–          The seeding depth is uniform, so that emergence is as synchronised as possible. A uniform seeding depth is more important than having an even distance between the plants on the same row.

Starter fertilisers are a useful method to secure rooting. What the starter provides is additional early vigour, when placed as a phosphate concentrate near the seminal roots. If crop establishment is slow (because of a long and cold spring, a cold or “white” soil that warms up slowly) or the seeds are planted in minimum till soils that warm up slowly, using starter fertilisers becomes crucial. In that case, they need to be placed at a reasonable distance from the seed (at 5 cm laterally and vertically).