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Harvesting Drought Stressed Maize

February 22, 2022

Harvesting Drought Stressed Maize

Time of harvest

In a typical year, the timing of harvest for maize silage is based on the milk line in the kernel and the dry matter (DM) of the whole plant. Two-thirds milk line (when the kernel’s outer two-thirds is starchy and the inner third milky) and 33-35% whole plant DM is the harvesting target most quoted for maize harvest. However, the plant can dry down faster in a dry year and become over 40% DM before the kernels reach the two-thirds milk line. In this situation, it is better to base the harvesting decision on whole plant DM% even if the kernels are still milky to ensure good silage stack compaction is achieved.

The maximum DM% at which good compaction can be achieved will depend on the storage site (stack or pit construction), the harvesting machinery (particularly adjustability of chop length), the type and weight of vehicles compacting the silage and the skill of the operator(s). Therefore, the silage contractor needs to decide when to harvest to ensure they can achieve good compaction.

When maize plants get quite drought-stressed, the plant can start to shut down before the cobs are ready. Once the plants are no longer accumulating nutrients, it is best to harvest the crop as it is.

A few tips for assessing maize crops

  • Always walk into the crop before checking plants, as the outer rows will not be representative
  • Where there is variation, e.g., in soil type or moisture, make checks in several areas to get an idea of average maturity and DM% for the crop as a whole
  • Use a thumbnail or pen nib to check where the milk line is
  • Tasting the white core in the plant stem can indicate whether the plant is still transporting nutrients (it tastes sweet) or the plant has shut down (it tastes like polystyrene)
  • Use a Koster DM tester or microwave to check the whole plant DM% pre-harvest (ask your Nutritech Area Manager for more details)

Maize that has a ‘pineapple leaves’ appearance can be an indicator that the plant is getting drought-stressed

Risks with drought-stressed maize

Drought-stressed plants are: –

  • More lignified (less digestible) with more sugar and less starch – so getting silage analysed will be more accurate than using average maize silage figures (your Nutritech Area
  • Manager can help with silage analysis)
  • More vulnerable to fungal disease, which gives an increased risk of mycotoxins, regardless of how well made and managed the silage is
  • More likely to have higher nitrate levels, leading to nitrogen dioxide production (an orange gas that can be lethal) in the first few days after ensiling.

Tools to help

Dry maize silage is more prone to aerobic spoilage, so selecting an inoculant that reduces the risk of heating at feed out can give a good payback. MAGNIVA® Platinum is scientifically proven to significantly improve the quality and aerobic stability of maize, whole crop cereal and other silages prone to heating. The proven Silostop® oxygen barrier sealing system reduces DM losses in the top metre by almost half, leading to more silage retained and a cleaner, healthier silage at feed out all with 33% less plastic.

There is also a risk of mycotoxin contamination. Using a proven mycotoxin binder such as Fusion® DYAD can help reduce the threat posed by multiple feed-borne contaminants such as Fumonisins, Ergot alkaloids and Zearalenone.

  1. Fusion DYAD® is registered pursuant to the ACVM Act 1997, No. A011062
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