Maize grown on the dairy farm can add value to farms feed supply, help mitigate climatic risk, extract soil nutrients from high fertility effluent paddocks, and be used as a ‘break crop’ in the pasture renewal process.
Maize should be fed to fill genuine feed deficits for economic responses and be well managed to reduce feed costs and wastage.
Considering costs and benefits
Maize cost can vary depending on where and how it is grown. If maize is grown on the dairy platform in an effluent paddock the cost could be as low as 12c/kg DM before storage.
Maize silage grown on effluent paddocks will significantly reduce fertiliser inputs. Maize silage can also be used to extract excess nutrients from effluent paddocks, as it removes large amounts of N and K, reducing risks of N leaching and occurrence of metabolic diseases. The opportunity cost of pasture not grown while is maize growing on the platform needs to be considered.
Maize purchased off-farm is generally more expensive. However, allowance needs to be made for the value of extra nutrients bought in with the maize and a reduction in risk due to maize being grown off the dairy platform.
Maize silage can be used to support pasture based systems at times of the year when pasture is unreliable e.g. maize on a feed pad when soils are wet, or fed in a dry autumn to build pasture cover.
On- farm management of feed potentially causes the greatest variation in feed costs. For example, a poorly managed stack can cause wastage amounting to a 30% increase in feed costs. Also, grass wasted through feeding maize silage at the wrong time can result in reduced profitability. For information on minimising loses during storage see the Maize silage page.
What factors affect maize yield?
Sowing location, sowing date, hybrid choice and population will all influence the potential yield of the crop. Potential yield can be reduced by weed and pest presence, moisture stress, disease, and nutrient limitations.
Maximising potential yield
To maximise potential yield we must maximise radiation interception (sunshine energy absorbed by the crop).
- Location: Temperature and radiation are different around the country. Often our growing location is fixed but if leasing or buying land for maize investigate the climatic conditions of the site.
- Sowing Time: This affects radiation interception, as radiation interception changes during the year. Radiation peaks late in December, so aim to sow your crop so that you have full canopy cover by this stage. In general, early sowing has higher yields than late sowing. However, this should be balanced against many factors such as: frost risk, soil conditions and pasture harvested pre-crop.
- Hybrid: The main difference between hybrids are is the number and size of leaves (which effects green leaf area), crop maturity (number of growing degree days (GDD) before the crop is ready to harvest) and ability to cope with stresses such as drought. As a general guide, short season hybrids tend to yield less because they have fewer smaller leaves than long season hybrids. They also tend to need fewer GDD’s to reach maturity so are in the ground for fewer days.
- Plant Population: More plants means more leaf area. Typical populations for maize silage is 100 to 120 thousand (k) seeds per ha.
- Other factors affecting potential yield includes weed pressure, drought, waterlogging, leaf diseases, nitrogen, pests, and soil structure. For more information, see pages 8-9: Best Management Practices for Growing Maize
What nutrients does Maize require?
Maize requires substantial nitrogen (N) and potassium (K), both of which are present in dairy soils.
On cropping farms N is the nutrient most likely to limit maize yields and is the largest fertiliser input. These inputs are generally not needed on dairy paddocks coming out on long term pastures. Up to 300kg N/ha is release from soil organic matter when high fertility dairy pastures are cultivated.
Maize is unlikely to respond to K fertiliser unless soil K test levels are very low. Replacement K fertiliser can be applied after harvest to avoid any luxury uptake by the maize crop.
Soil test for N before applying post emergence N fertiliser to determine if any is required. There are two soil tests regularly used for maize:
- Basic soil test (0-15cm) for pH, Olsen P, K, Ca, Mg etc.
- Deep N test (0-60cm) for mineral N.
Dairy effluent can be used as a nutrient source for maize, provided the crop requires the nutrients and good effluent practices are followed.
For more information of nutrient requirements and dairy effluent for fertiliser see pages 12-14, Best Management Practices for Growing Maize.
What pests, diseases, and weeds should I look out for?
At emergence check for slugs, bird, and rat damage. Slugs are not generally a problem where intensive cultivation has been carried out but can do serious damage during wet weather and if reduced tillage practice have been used. Bird and rat damage is characterised by plants pulled and seed embryo eaten.
Paddocks out of long term pasture often have a broad-leaf seed bank while paddocks that were run-out pastures often have grass weeds e.g. summer grasses. Weeds can cause a significant yield loss, and moisture activated pre-emergence herbicides generally work well, however in some situations, further post-emergence applications are required.
At emergence of four leaves
Monitor for slug and bird damage but also check for greasy cutworm and weeds. Greasy cut worms feed at night by typically cutting and felling maize plants.
See the AgPest website for more information.
Monitor for leaf diseases in mid to late December if the weather is warm and humid. Monitoring for common rust, eyespot, northern corn leaf blight is important unless resistant hybrids have been used. Fungicides will give control but are seldom used unless environmental conditions are particularly favourable to disease.
Generally, around the 20-30th of December is the time to check for army worm caterpillar, especially if crops are weedy. Note corn-ear worm often appears in January as cobs are pollinated. Corn-ear worm is generally controlled by parasitic wasps and should not be confused with army worm.
Three weeks Prior to harvesting
It is vital that maize crops are checked for harvest maturity. Good quality maize silage is best made when whole plant dry matter is between 30-40%. If harvested at less than 30% the silage stack will be wet resulting in stack leachate, this leachate represents nutrient loss. If greater than 40% DM, stack compaction and air exclusion is much more difficult.
In field estimation of crop DM requires considerable experience, most contractors and technical advisors have experience in harvest scheduling.
For more information, including the maturity indicator, maize kernel milk, see page 17 Best Management Practices for Growing Maize.
Maize seed is normally sown around 5cm deep. An uneven soil surface (undulations, ruts etc.) makes it difficult for the planter to sow at a uniform depth resulting in variable emergence. Maize does not need a very fine seedbed, it is a large seed and seed to soil contact is generally sufficient for germination, except on very cloddy soils. Light rolling after sowing may help seed-soil contact, seal in moisture and reduce risk of wind erosion.