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This article was compiled by Pioneer Agronomy
Farmers need mealies that can perform better in short planting seasons with more sustainable cultivation practices, but these new tendencies are also accompanied by new challenges.
Earlier planting, accompanied by sustainable conservation cultivation systems, may increase the risk of uneven lower-yielding plant stand with concomitant lower yields. Typically soil temperatures are then much lower than the optimum of 29°C before emergence. Soils with thick residue cover are much wetter and colder than uncovered lands in early spring. This causes more cold stress and disease pressure.
Disproportionate plant rest cover on the lands also result in variations in planting depth, which leads to uneven emergence and arrested plant growth – at least one leaf late. To ensure the establishment of a good plant stand these risks should be dealt with by means of positive management practices.
Cultivar selection for lands with heavy plant rest cover
The Corteva Agriscience Research Unit undertakes annual extensive maize plant emergence trials over a wide range of stressful environments and soil types, including early planted lands and lands under reduced cultivation.
Data from the stressful area(s), as well as laboratory tests that imitate stressful conditions, are implemented to allocate a stress handling count to cultivars. This is based on genetic potential of a cultivar to establish under stressful conditions such as cold, wet soil with short intensive cold periods.
These tension counts vary from 1 to 4 (under-average), 5 to 6 (average) and 7 to 9 (very good potential) to attain normal plant stands during stress conditions. Thus cultivars with counts from 1 to 4 will not be recommended when severe cold, wet conditions are expected after planting.
In emergence trials undertaken in areas with high tension conditions, cultivars with higher counts were able establish better stands than the lower count cultivars (Figure 1).
In the Corteva Agriscience emergence trials under high plant rest conditions Pioneer varieties with a low HRS count (X) gave lower plant stands compared with cultivars adapted for a plant rest cover (S), or highly adapted (HS) irrespective of temperature tension levels (Figure 2).
Arrested plant growth
Mininised tilling systems may also result in uneven plant stand and arrested plant growth. In the Corteva Agriscience trials cultivars with an HS count resulted in fewer stunted plants (plants with at least one leaf less) compared with the adapted cultivars (S) and weakly adapted (X), as indicated in Figure 3.
Emergence under tension
Genetic potential of a cultivar to establish a stand during stress conditions (1 to 9 scale):
7 to 9 = Good emergence potential;
5 to 6 = Average potential; and
1 to 4 = Lower than average potential.
High residue adaptability
Counts for cultivar performance in diminished tilling systems:
Highly suitable (HS);
Suitable (S); and
Poorly suitable (X).
Suitability counts are based on field observations and weighed calculated counts of scores for:
• Resistance against grey leaf mould;
• Tension during emergence;
• Anthracnose stem rot;
• Northern leaf blight; and
• Diplodia ear rot.
High residue adaptability counts may vary between environment and geography.
Planting on high residue lands
Low intensity cultivation systems pose challenges to farmers. Lands with heavy plant residue loadings may prevent planting efforts as indicated in Figure 4.
Planting problems such as hairpin, sidewall compaction, loss of consistent plant depth and failure of properly closing up the planting furrow to cover the seed, will all prevent critical soil/seed contact.
The application of row cleaners (to clean the planting furrow of plant rests) can assist the planting process and assist emergence by removing physical hindrances on the soil surface. This can also assist in warming the soil after a cold spell (Figure 5).
Spiked or spider-type row cleaners can be advantageous in heavy clay soils. It can be adjusted in such a way that they move the material without disturbing the soil, which will bring about heating and drying-out in the row.
Floating row cleaners, which are better in following the land surface contours, are available from some equipment suppliers.
When planting is done a little deeper (at least 5 cm deep) it could assist in negating the variations in moisture and temperature near the soil surface.
An aggressive adjustment on the down-pressure wheels may be necessary to ensure that the wheels keep firm contact with the soil. It is also important to ensure that the seed is placed in the correct position in the furrow.
Seed covering wheels
Different variations of seed tamping wheels are available to close up the planting furrow depending on the physical soil characteristics and moisture content. Spiked wheels perform better on heavy, wet soils where side wall compaction is reduced while the plant row is being covered up. However, the farmer may also use one spiked wheel and one rubber wheel.
Because of the impact on stand establishment and yield the selection of a planting date is one of the most important aspects of the farmer’s management decisions. When planting takes place while the soil is too wet, it influences the covering up of the planting furrow as well as side-wall compaction.
Enough time should be allowed for soil with abundant plant rests to dry off sufficiently before planting. Soil temperature data collected on Corteva Agriscience trial plots confirm that plant stand is adversely affected when planting is done with the soil temperature at 10°C or lower.
Weather patterns should be monitored to determine tendencies. Snow, cold, rain or long periods of cold weather after planting result in elemental tension for maize seedlings.
Effective residual material management practice is essential to utilise the advantage of reduced residual material management practice. The choice of the correct cultivar, as well as the necessary adjustments to the planter, all combine to ensure a good plant stand on the lands with plenty of residue.
The quick-growing yellow irrigation cultivar, P1197, has the excellent characteristics dealt with in this article. It gives a strong seedling that emerges quickly from the soil compared with quite a number of good irrigation cultivars, including hybrids bred by competitors.
• Cultivar choice is of vital importance to attain a productive stand with high yield potential on lands with abundant plant material on the soil;
• Corteva Agriscience Research plant early trials on lands with thick residue to evaluate cultivar performance during early seasonal tension conditions;
• Pioneer cultivars with well-adapted (HS) and adapted (S) counts for thick residue, result in improved stands in an environment with plenty of plant rests compared with products with lower (X) ratings;
• High plant rest environments are more generally tied to uneven emergence and delayed plants as a result of uneven plant depths, temperature and moisture variations as well as physical material obstructions;
• The utilisation of row cleaners and other planter mechanisms may improve soil contact, enhance soil warming and lower delayed plant development, and
• When planting in soil with a temperature above 10°C, or during a warmer period, it speeds up quicker and more even emergence on lands with high plant residue.