Making better conserved forage campaign – Maize focus

Published 19 September 18

Following the dry and hot summer, maize harvesting is likely to be a couple of weeks earlier this year. In a year of feed shortage, accurately assessing crop maturity before harvesting to make sure you make the most of this valuable crop is critical.

As the crop matures, the quality of stem and leaf declines, but this is offset by the increase in grain in the cob, which is highly digestible and high in starch. This is why harvesting at the correct stage is essential, to maximise nutritional value.

The ripeness of the cob will indicate true maturity and it is important to ensure the crop is harvested at the correct maturity to maximise starch levels. Maize should be harvested when the dry matter (DM) content of the whole crop is between 28 – 35 per cent. This is best assessed by drying a representative sample (200 – 500g of cut-up material) in an oven or microwave:

  1. Weigh the sample before and after drying.
  2. Divide the final weight by the initial weight.
  3. Multiply by 100.

More information on these methods and a step to step guidelines are available in the BRP manual Growing and feeding maize silage for Better Returns

Typically, the DM% of a maize crop increases by about two per cent per week at harvest time. Having assessed the DM%, the harvest date can be predicted.

The alternative, 'milk line test' is commonly used as a guide out in the field. However, with the recent rain encouraging secondary growth and greening in some cases, the maize growers association warns that this method should not be solely relied upon this year.

Mize Image 1


Table 1. How to work out when maize is ready to harvest (Source: Maize Growers Association)

Keep an eye on the weather forecast to avoid harvesting in wet conditions which can cause damage.

Chop length can have a big influence on the performance of the maize and the stability of the crop in the clamp. It is important to consider factors such as DM% and the amount of maize that will be fed in the diet when determining chop length. Keep the chop length shorter with drier crops in order to aid consolidation, but you can get away with a longer chop length with wetter crops.

Talk to your nutritionist about which chop length is best suited to your system (typically 12 – 18mm) and then talk to your contractor to make sure they can meet those requirements. Additionally, make sure you check the chop length on the first load into the clamp.

When ensiling, it is important to fill the clamp quickly, consolidate well to remove air and seal completely for rapid, anaerobic (without oxygen) fermentation. Maize silage ferments well unaided and does not typically require an additive. However, additives can reduce aerobic spoilage, particularly if the clamp is wide and the maize is taken out slowly. There are certain scenarios when additives may help to maintain feed quality (Table 2).

Table 2. Situations where silage additives may help maintain feed quality

 Maize Image 2

The digestibility and starch content of maize silage improves with time in the clamp. Ideally, maize silage should be left for at least a month before feeding to allow pH and feed quality to stabilise. Research demonstrates that the starch digestibility of maize silage improves with the length of time spent in the clamp. However, unlike grass silages, it can be fed immediately if needed urgently to fill a feed deficit.

Having an accurate nutritional analysis of conserved forages is essential when formulating rations so that they are used appropriately, accurately and in a cost-efficient manner. For more information on feeding principles download the BRP manual Growing and feeding maize silage for Better Returns.