Back Getting it right - from planting to harvest

Date: 12 April 2018

Hybrid selection is important for maize silage growers and users alike as it will have a huge impact on silage yield, quality, cost per kilogram of drymatter, crop return per hectare and dairy farm profitability. When selecting a maize silage hybrid farmers should consider the following factors:

Hybrid maturity and agronomic traits

Begin by identifying a group of hybrids which have the correct maturity and high ratings for the agronomic and disease resistance traits that are important in your area. This will help ensure stable yields from one season to the next. In making the call on hybrid maturity remember to consider the planting date needs of the following grass crop.

Seed quality

Maize hybrids may vary genetically in their ability to germinate and grow rapidly in our cool, wet spring soils. It should, however, be noted that differences in seed germination and vigour are also influenced by seed harvest timing, handling, drying, conditioned storage and seed treatment. Genetic impurity or off-type plants within a hybrid may also cause yield loss. Growers can plant Pioneer® brand maize hybrids with the assurance that their seed has been produced in Gisborne to the highest international standards within Pioneer for genetic purity and germination.

Total drymatter yield

From those hybrids that meet your maturity and agronomic requirements, select 3 or 4 hybrids that are expected to give you the highest total drymatter yield. Hybrid selection decisions should be based upon maize silage summary data. Side-by-side comparisons conducted over several seasons at 20 or more locations, in your growing region will give an excellent prediction of future performance.

Nutritional quality

Maize silage hybrids differ in a range of nutritional characteristics including starch, whole plant digestibility and ME (Metabolisable Energy). Silage quality characteristics should only be compared between hybrids that have similar maturity, agronomic
characteristics and side-by-side yield performance. From a nutritional standpoint, the best silage hybrids will have high energy and digestibility ratings. The trait table on page 35 presents starch and soluble sugars and whole plant digestibility ratings based upon the annual analysis of over 2,500 samples in our New Zealand silage hybrid evaluation programme.

When to harvest your silage crop

Attention to planting date, plant population, fertility and weed control will set your crop up for the delivery of optimum yields. The final step for silage growers is harvest timing.

• Ideal harvest time is when your crop is between 33-38% drymatter, though harvesting as low as 30% drymatter is not uncommon.

• As silage harvest time approaches, yield accumulation slows. From the graph on the following page if your maximum yield is 20 tDM/ha harvesting at 33% vs 35% drymatter will only impact yield by 100 kgDM/ha.

• It should be noted if the crop has been drought stressed the drymatter percentage may not be consistent with the milk line progression.

• In addition, crops that are shorter than normal with relatively large ears may have higher than expected drymatter.

• If a season is very conducive for high grain filling (high radiation levels and abundant moisture) drymatters of more than 38% are not uncommon. Provided the plants are still green, compaction will not be a problem and quality may be enhanced due to higher grain content.



The milk line forms as a visible separation between hard starch and soft starch. It forms at the crown of the kernel and progresses toward the base, or the kernel tip attached to the cob. The milk line stages are generally referred to as ¼ milk line, ½ milk line, or ¾

milk line as it moves toward the cob. The hybrid will generally be ready for harvest when the milk line is two thirds of the way down the kernel.

Determining the milk line

• Take a cob from a plant at least 20 rows into the crop. The cob selected should be from a plant in a uniformly planted row.

• Break/snap the cob in half and discard the end of the cob that was attached to the plant.

• Hold the point of the cob downwards and slide your fingernail along the length of the kernel starting at the flat or dented end.

• Note the point where the solid starch ends and the liquid milk begins. The hybrid will be ready for harvest when the milk line is two thirds of the way down the kernel.

The milk line test is only indicative that harvest time is near. The only sure way to test plant drymatter is though the microwave test or by sending a plant a suitable laboratory.