Guide for corn variety selection – Factors and characteristics to take into account for choosing the most appropriate variety of maize.

The selection of the cultivated maize variety is one of the most critical human-controlled factors affecting crop production. A careful variety choice can upgrade a farmer’s production in the long run and/or protect the yield in case of external-uncontrollable factors (e.g., diseases, environmental stresses, etc.). There are thousands of maize varieties available in the market, while new ones are constantly created by plant breeders globally. From 2012 to 2022, the International Maize and Wheat Improvement Centre (CIMMYT) and the International Institute of Tropical Agriculture (IITA) have developed 604 maize varieties in 33 countries (https://maize.org/)

The first categorization of Corn varieties has to do with biological cycle and FAO number. We have varieties of 300-400-500-600 or 700 FAO. In a few words, if we have a big FAO number, the growing season of the corn will be longer, and we normally need more heat compared to smaller FAO numbers. On the opposite, the more we move north or to higher altitudes, the less heat units our crop can enjoy, so we shall choose an earlier variety with smaller FAO number. As a rule of thumb, a longer growing season results in higher yields, but also higher costs (irrigation, fertilization, pest management etc.). 

There are two main categories of maize varieties:

  1. Open Pollinated Varieties-OPVs and 
  2. Hybrids

Open-pollinated varieties were mostly used until 2000 due to the easy and low-cost way of development and reproduction. The intensification of maize cultivation and the prevalence of monoculture have established hybrid maize varieties as the main choice, especially in regions like the USA and Europe, due to the higher yield that they offer. However, new research data show that in systems like agroforestry, the open-pollinated corn varieties can perform equally well with the hybrids (Ndoli, 2019). 

As a result, a farmer can find numerous maize varieties available to satisfy many of the modern needs for successful maize production. However, the selection of the variety should be based on factors like the characteristics of the variety, the local environment of the field we want to cultivate our maize, and finally, the cultivation system (organic, conventional, etc.), keeping also in mind the available inputs (fertilization, irrigation, etc.) that we can offer to the crop.

For example, a variety X might be the best choice for an area with plenty of rainfalls, but it will not reach its potential yield in an area with excessive drought-heat and limited availability for irrigation. Similarly, a farmer should take into account, before making a decision, the “enemies” (pathogens, pests, and weeds) of the crop that thrive in the area. Many varieties have different sets of resistant genes against specific plant diseases, and others carry characteristics that make them more competitive against weeds. This is especially important for farmers that want to decrease the use of chemical pesticides and herbicides.

Consequently, we should always keep in mind that not all varieties are suitable for all environments or/and cultivation systems (no-tillage, organic, etc.). In general, the maize variety we will choose to sow into our field should offer a satisfactory-good yield without the excessive use of inputs like fertilizers, irrigation, and pest management products. This way, the choice of the variety has a principal role in the crop’s sustainability status and the farmer’s profit (fewer expenses → more profit).

List of Important traits to take into account when choosing a Corn variety

The cultivar-variety choice should be based on yield, quality, and agronomic characteristics-behavior of the variety. More specifically, the traits of high interest for maize are:

  • Yield potential of the maize variety
  • Adaptability (varieties with wide adaptability are suitable for a diversity of conditions). The adaptability of a maize variety depends on the plant’s tolerance to environmental stresses (e.g., drought, heat, frost, etc.).

When we say that a variety has wide adaptability, this means that it can reach a good-stable yield in a wide variety of conditions. The stable yield from year to year is a trait-characteristic of high importance, especially for a farmer of contract agriculture (preselling the future production). In low-density management strategies applied in drought areas, reproductive plasticity (the yield produced per unit of resource input-available) is an important characteristic of the variety selected.

  • Corn Ear Prolificacy 

This trait links both with the adaptability and the yield of maize. During the domestication of maize, one of the characteristics that changed significantly was the number of ears per plant (ears=female inflorescences?maize spadix). In the case of maize, this number decreased, with some commercial varieties for intensive agriculture systems having 1-2 ears per plant (Iltis HH – 1983). However, in low plant density and limited nitrogen fertilization systems, the increased ear prolificacy can stabilize the total maize production (Parco 2020).

  • Length of the crop life (can be referred to as CRM= Cumulative Relative Maturity, in days, or as Maturation time) and planting date of maize.

Depending on the area of cultivation, the farmer should take into account the weather and temperature mainly at the start (sowing-emergence) and at later stages (flower, fertilization and maturity) of the crop cycle (=cultivation period). If the temperatures are still low during sowing, the farmer should choose a variety with relevant tolerance. Similarly, in warmer climates, the most popular varieties have resistance to high temperatures and drought.

  • Lodging resistance (can be described or be relevant to Stalk strength, Cob height, Stability)

For maize, like in other grain crops, the ability of the plants to endure strong winds and maintain their vertical position can dramatically affect the final yield. If the stem or the whole plant bend near the ground, there is an increased risk of a disease outbreak (due to bad aeration) and losses during harvest. Keep in mind that the risk of Lodging also depends on the plant density of the crop ( read more here, 10).

  • Disease resistance against major corn pathogens

The variety selected should be tolerant or resistant to a range or to specific diseases such as ear rot, maize streak virus disease, grey leaf spot, rust, cob-and-tassel smut, stem rot, and root rots. Not all varieties are similarly resistant to all diseases. Farmers should be aware of which are the most common and prevalent pathogens in the area they want to cultivate maize. However, the performance of a variety against a pathogen should have been tested under field conditions (the characteristics and rating of the variety for a specific pathogen resistance might be different between lab and field conditions – read the rating carefully). 

  • Weed tolerance – Resistance to Striga- witchweed

Striga is a parasitic weed and one of the major “enemies” of maize, causing countless yield losses each year globally. Scientists are currently testing the use of imidazolinone-resistant (IR) maize seed with promising results (11).

  • End-Commercial use of the maize grain (livestock feed, food, bio-fuel production, starch or oil production)

Depending on the final use of the grains produced, there are different desirable sets of characteristics (Organoleptic characteristics, the chemical composition of the grain, etc.). For example, maize that is cultivated for livestock feed needs to have a high protein (zein) content in maize grain (feed quality of maize variety). However, it is essential to remember that many quality characteristics can be affected to some extent, from the cultivation and storage practices that the farmer follows Győri, Z. (2017). 

Some of the standard characteristics describing the performance and grain quality of maize varieties are:

  1. The Dry Matter (DM) content at harvest (you will find it as a percentage number that usually ranges up to 38% for forage maize). 
  2. The actual Dry Matter yield [is expressed as tons per hectare (t/ha), and this number ranges up to 20].
  3. Metabolizable energy (ME) of a fresh plant at harvest. It is the energy value of silage measured in MJ/kgDM.
  4. Starch content or/and starch yield of the whole plant at harvest.
  5. Cell wall digestibility (%). The higher the number, the better since the high digestibility of the fiber highly influence the nutritional value of the forage (Barrière, 2003).
  6. Early vigor of the plant. The higher (up to 9), the better because it also reflects the competitive ability of the crop against weeds.
  7. Standing power at harvest (root lodging). In this case, the character is graded on a scale from 1 (poor) to 9 (good). The ability of the crop to maintain its vertical position (easier harvest) is also described by the Lodging (%). In this case, we need the number to be as low as possible.
  8. Brackling (%). It is the kinking or buckling of the stem at/around the nodal areas close to the time of harvest. This number should also be as low as possible since it reflects yield losses and problems during maize harvest.
  9. Leaf senescence. The characteristic is graded on a scale from 1 (green leaves) to 9 (advanced senescence-dried leaves-plants). A synonymous term is the Stay-Green (delayed leaf senescence). This characteristic has positively correlation with higher yield (grain and silage production), quality, and stress resistance of the plants. The reason for this is that the plant can  be photosynthetically active for a longer period of time, a characteristic especially important for short- period (early maturation) maize varieties. However, based on scientific data, there might be a negative effect of stay-green on the nitrogen content of the corn grain, an issue that it is resolved thanks to the higher uptake of N after flowering (Chibane, 2021).

You can find BSPB Forage Maize Descriptive List with maize varieties available in the market here (9).

Genetically modified maize varieties (GM)

After soybean, maize is the second most widely cultivated genetically modified (GM) crop. GM maize varieties have been available in the market already since 1996, and until today they carry resistance genes for pest tolerance, herbicide resistance, and, most recently (2013), drought tolerance. More specifically, the pest-resistant transgenic maize varieties confer HT- or/and Bt-mediated insecticidal activity. This trait is usually combined with herbicide tolerance for the crop. Finally, a new line variety was created by stacking together eight transgenes offering multiple resistance against major corn pests (Moglia 2016).

As in other crops, all genetically modified maize varieties cannot still be cultivated in numerous countries worldwide, and of course, they are strictly prohibited in organic agriculture systems. The farmer should make a research concerning the current legislative framework around GM in his/her country and examine the market demand for such products since many countries do not import GM products.

Tip:

In any case, it is highly advised to test the one or multiple varieties you have chosen in a smaller field area before using it as your main variety for cultivation. This test will give you a better picture of how this variety behaves in your field. 

References

  1. Ndoli, A., Baudron, F., Sida, T. S., Schut, A. G., Van Heerwaarden, J., & Giller, K. E. (2019). Do open-pollinated maize varieties perform better than hybrids in agroforestry systems?. Experimental Agriculture, 55(4), 649-661.
  2. Moglia, A., & Portis, E. (2016). Genetically Modified Foods. Encyclopedia of Food and Health, 196–203.
  3. https://www.arc.agric.za/arc-gci/fact%20sheets%20library/maize%20production.pdf   
  4. Iltis HH (1983) From teosinte to maize: The catastrophic sexual transmutation. Science 222:886-94
  5. Parco, M., Ciampitti, I. A., D’Andrea, K. E., & Maddonni, G. Á. (2020). Prolificacy and nitrogen internal efficiency in maize crops. Field Crops Research, 256, 107912.
  6. Győri, Z. (2017). Corn: Grain-Quality Characteristics and Management of Quality Requirements. In Cereal Grains (pp. 257-290). Woodhead Publishing.
  7. Chibane, N., Caicedo, M., Martinez, S., Marcet, P., Revilla, P., & Ordás, B. (2021). Relationship between delayed leaf senescence (Stay-green) and agronomic and physiological characters in maize (Zea mays L.). Agronomy, 11(2), 276.
  8. Barrière, Y., Guillet, C., Goffner, D., & Pichon, M. (2003). Genetic variation and breeding strategies for improved cell wall digestibility in annual forage crops. A review. Animal Research, 52(3), 193-228.
  9. https://www.niab.com/research/agronomy-and-farming-systems/variety-evaluation-and-management/bspb-forage-maize
  10. https://www.mdpi.com/2073-4395/12/1/10/pdf
  11. https://repository.cimmyt.org/bitstream/handle/10883/19063/58902.pdf?sequence=1&isAllowed=y

Fast Facts and History of Maize

Maize Nutritional Value and Health Benefits

Corn Plant Information and Production

How to Grow Corn for Profit – Maize growing guide

Principles for selecting the best maize variety

Maize Soil preparation, Soil requirements and Seeding requirements

Maize Pests and Diseases

Maize Water Requirements and Irrigation Systems

Maize Fertilizer Requirements

How to successfully control weeds in corn cultivation for higher yields

Yield, Harvest and Post-harvest handling of Maize

OUR PARTNERS

We join forces with N.G.O.s, Universities, and other organizations globally to fulfill our common mission on sustainability and human welfare.