Best Management Practices for Growing Maize on Dairy Farms

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Deep soil (0-60 cm) mineral N testing canalso be carried out while pest and weedmonitoring (chapter six) to plan post emergencefertiliser N application.4. Six leaves with visible collars (V6)From V6, the crop grows very rapidly andwith time eliminates vehicle access intothe crop. High clearance sprayers or aerialapplication become the only options.If further N fertiliser is required, thenmake sure it is applied by this growthstage. Monitoring can also be done duringfertiliser application and sometimes postemergenceherbicide applications are alsoapplied with the fertiliser.5. Mid to late DecemberLeaf diseases (if warm and humid) appearduring this time. Monitoring <strong>for</strong> commonrust, eyespot, and northern corn leaf blight(more common in long term maize land) isimportant if less resistant hybrids have beenused. Fungicides will give control but areseldom used unless environmental conditionsare particularly favourable to disease.Generally around the 20-30th December isthe time to check <strong>for</strong> army worm caterpillarespecially if crops are weedy. Note thatcorn earworm often appears in Januaryas the cobs are pollinated. They are generallycontrolled by parasitic wasps. Cornearworm should not be confused witharmyworm.Armyworm caterpillars - green, then greenishbrown when older.Corn earworm.6. IrrigationWhile generally not practised in most NorthIsland dairy regions, irrigation is common inCanterbury. Inadequate moisture (when thesoil moisture falls below half the soil waterholding capacity) at any growth stage canreduce maize yield. It is advisable to run awater budget or schedule based on 50%of plant available moisture linked to weekly16
evapotranspiration rates (ET). Moisturestress can also result in a lack of synchronisationbetween pollen shed and silking atpollination.7. Silking dateOne important maturity indicator is themaize kernel milkline, where the milkyliquid changes to the harder darker starchline. By simply snapping a cob in two andexamining the upper portion’s kernels, themilkline can be seen. When the milkline isone third of the way up from the bottom ofthe kernel the plant is in the 28 to 32% DMrange. However, other indicators need tobe considered (including those mentionedearlier) such as the hybrid, the husk covercolour, the greenness of the leaves andstem.Silking date is the date when 50% of the plantsare showing silk at the tip of the young embryoniccob.1/ 3 rd Liquid milkThe date when 50% of the plants are silking(refer to photo) should be noted. <strong>Maize</strong>generally takes 50-55 days from this timeto reach two thirds milkline, an importantindicator of crop maturity.<strong>Maize</strong> kernel milkline.2/ 3 rds Solid starch8. Three weeks prior to harvestIt is vital that crops are checked <strong>for</strong> harvestmaturity. The AmaizeN calculator and 50%silking date will greatly aid in determiningwhen to start frequent monitoring. Goodquality maize silage is best made when thewhole plant Dry Matter (DM) is between 30and 40 %. If harvested at less than 30%DM, silage in the stack will be wet resultingin high stack leachate, this leachate representsnutrient loss. If greater than 40%DM, stack compaction and air exclusion ismuch more difficult.In-field estimation of crop DM requiresconsiderable experience as; changes insoil type, topography, proximity to trees orhedges, the hybrids cob to stover (vegetativeparts) ratio and time of day, all need tobe taken into account. However, by examiningplants in representative areas goodestimates can be made.Most contractors and technical advisorshave experience in harvest scheduling.Dairy farmers would be wise to seek theiradvice in this area.17
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Best Management Practices for Growing Maize on Dairy Farms

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