Maize for Silage
Technical
Insight 335

PIONEER RESEARCH UPDATED MAIZE SILAGE CUTTING HEIGHT

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INTRODUCTION

Maize silage crops are normally cut about 100 mm above ground level.  This gives maximum crop yield for any maize hybrid.  However, by altering harvest height, it is possible to alter maize silage drymatter content and feed value.  The aim of this study was to investigate the effect of three cutting heights on the yield and quality of a range of Pioneer® brand maize silage hybrids available for sale in the 1999/2000 seasons.

TRIAL RESULTS

In a study conducted during the 1999/2000 season, maize silage hybrids were cut at 100, 300 and 600 mm above ground height.  A total of 216 samples were weighed and samples were submitted for drymatter determination.  The results (across all hybrids) are presented in Table 1.

Table 1: Effect of a range of cutting heights on maize silage yield and drymatter content

Cutting height

Silage yield (tDM/ha)

Silage drymatter (%)

100 mm

22.45

35.73

300 mm

21.46

37.22

600 mm

19.94

39.16

Increasing the cutting height from 100 mm to 300 mm increased the drymatter content by 1.5% because more of the wet stem material was left in the paddock. The yield decreased by 1 tDM/ha.

Increasing the cutting height from 100 mm to 600 mm increased the drymatter content by 3.43% and decreased the yield by 2.52 tDM/ha.

This study did not include any nutritional analysis however, since the base of the stalk is one of the less digestible parts of the plant, increasing the cutting height would have resulted in a higher feed value.

The gain in feed value can be estimated as follows:

Let’s assume that the 100 mm silage had an ME content of 10.8 MJ/kgDM and that the ME value of the stalk left behind was 7.5 MJME/kgDM.  Table 2 shows the effect of lifting the cutter bar on the ME/kgDM and per hectare yields.

Table 2: Effect of a range of cutting heights on maize silage ME/kgDM and ME/ha

Cutting height

Energy per kilogram drymatter (MJME/kgDM)

Energy per hectare (MJME/ha)

Milksolids per hectare (kgMS/ha)

100 mm

10.80

242,460

1,796

300 mm

10.95

234,987

1,741

600 mm

11.21

223,574

1,656

*Assumes a milksolids response of 1 kg milksolids per 135 MJME fed.

USING CUTTING HEIGHT TO MANIPULATE TIME OF HARVEST

Since cutting height affects maize silage drymatter content, it can be used to manipulate days to silage harvest. Normally maize silage hybrids increase in drymatter at a rate of 0.2 - 0.5% per day.  Therefore a maize silage crop will reach 30% drymatter around 2 - 5 days sooner if it is cut at 300 mm or 5 - 13 days earlier if it is cut at 600 mm.

A long maturity hybrid harvested at 300 mm cutting height could be ready for harvest at about the same time as a 4 - 5 CRM shorter maturity hybrid harvested at 100 mm. 

OTHER CONSIDERATIONS

Longer maturity hybrids have a higher yield potential than short maturity hybrids given good growing conditions and plenty of summer heat. Many farmers choose to plant a short maturity hybrid because they have a fixed planting date and a target harvest date. In a warm season, a longer maturity hybrid may reach harvest drymatter within the target growing period. If this is the case it will out-yield a shorter maturity hybrid.

If the heat accumulation during the growing season is “average”, harvesting a longer maturity hybrid at 300 mm will result in a similar net return per hectare. If harvest is delayed for any reason, the harvest height can be reduced increasing yield and decreasing drymatter percentage.  A short maturity hybrid will continue to increase in drymatter with little or no yield increase. Delayed harvesting may result in poorer silage quality.

For both 300 and 600 mm harvesting heights, additional stubble will be left in the fields. This may be advantageous especially in a continuous maize silage-cropping regime. Harvesting at 600 mm can pose problems for machinery in that the long stalks can damage the undersides and tyres of vehicles.



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Revised: June 2015
Expires: June 2018