Planning for next summer’s forage crops starts now. This was the message given to farmers at a recent Beef + Lamb New Zealand Central Canterbury Farming for Profit workshop focusing on summer crop management.
Crops such as forage brassicas, red clover, chicory, plantain and grazing maize fill feed gaps, particularly in summer dry environments and are valuable for finishing lambs, putting body condition back onto ewes, managing internal parasites and as part of a pasture renewal programme.
Caitlin Thistoll, an agronomist with Ballance Agri-nutrients, recommends farmers carry out soil tests in paddocks ear-marked for growing summer forage crops six to 12 months out from sowing. For brassica and maize crops, soil should be tested to a depth of 150mm.
“It is important to know your starting point and then you will know what nutrients could be lacking and therefore limiting production.”
Weed control also starts at the initial planning phase. The weed profile of a paddock can help determine what crop to grow and pre-establishment weed control options.
Crop establishment
Typically established in spring, factors to consider before sowing a summer forage crop include the purpose of the crop, the weed profile, soil moisture, methods of establishment and pests.
Fallow can be useful tool where soil moisture is lacking as it allows what little moisture there is to accumulate in the soil. Rolling can draw moisture to the surface before and after drilling and allows sowing depth to be controlled, which also aids establishment. Direct drilling, rather than conventional tillage, can also help conserve soil moisture.
Fertiliser applied at drilling can either be in an all-in-one granule form or compound fertiliser, which is a blend of superphosphate, potash and micronutrients in separate granules. There is typically a 20% greater response to compound fertilisers over all-in-one granules.
Pre-establishment insecticides and treated seed will help prevent insect damage until the plants get to the four-leaf stage. Regular monitoring is critical, particularly in that early establishment phase before canopy closure.
Brassicas
Brassica crops need a soil pH of 5.8-6.2, an Olsen P of 15-26, potassium (K) of 4.8, sulphur (S) levels at 2 (soil sulphate test), magnesium 8-10 and boron 1.1.
Where Olsen P levels are in single digits, it might not be economic to grow a brassica crop until fertility has been corrected.
Even where nutrient deficiencies have been addressed, Thistoll says ideally brassicas should be sown with fertiliser.
“Brassicas are poor scavengers of nutrients such as phosphate.”
Boron is also important for brassicas. This trace element helps prevent Brown Heart Rot and is needed for carbohydrate metabolism and cell wall integrity.
Applications of nitrogen (N) at sowing, and as a side-dressing to drive canopy closure, will help optimise crop yields in brassicas.
Thistoll recommends testing for available N when carrying out soil test to help determine crop requirements at and after establishment.
N should be applied before rainfall to avoid losses to volatilisation. Around 8mm of rain within 24-48 hours of application is ideal.
There are options to apply N in liquid form directly to the leaves (foliar applications), but it is still preferable to have moisture even after this has been applied.
Grazing maize
Grazing maize can be a valuable cattle feed. Sown in October (when there is no risk of frosts), it is grazed when the crop reaches hip height, usually after Christmas. Target yields are 8-14t/ha. Maize has an ME of 10.5ME which is not high, but better than rank grass. One of the advantages of grazing maize over harvested maize is that the nutrients stay in the paddock.
Soil tests should be taken six to 12 months out from crop establishment.
Maize requires a soil pH of 5.6-6.2, an Olsen P of over 15, potassium over 4, sulphur 6-10 and magnesium 8-10.
To help achieve target yields, Thistoll recommends N applications of 100-150kg N/ha.
Clovers and chicory
Thistoll says chicory can be treated like a pasture in terms of N applications and she recommends dressings of 25-30kg N/ha applied.
Boron and molybdenum are also important trace elements for legume crops. Nitrogen can be used to help in the establishment of clover crops, before the plants start fixing their own N.
Animal production
Summer forage crops such as chicory, plantain, clovers and brassicas are higher in protein than ryegrass and they have faster rumen degradation rate, so lambs can eat more over a 24-hour period.
Ryegrass has a rumen degradation rate of around six hours while brassicas, chicory and clovers have a rumen degradation rate of around 2.5 hours.
With the correct management, it is possible to grow lambs at 300gms/day on specialist forage crops. This helps drives efficiencies as lambs that are finished faster eat less total drymatter over their life than lambs growing at 100gms/day.
To make the most of summer forage crops factors to consider include the accurate allocation to ensure stock are fully-fed without posing animal health risks, transition time – ideally 10-14 days, clostridial vaccinations, particularly for lambs, and grazing withholding times where agrichemicals have been applied.
Herbage tests will provide detailed information on the nutritional value of summer forage crops and help inform decisions around feed allocation and supplement requirements.
Carrying summer forage crops into winter
Crops such as rape and kale can be carried through into winter, or farmers could consider stitching ryegrass or oats into summer rape crops and have a high-quality feed in spring. An agronomist will provide advice around sowing options.
Other mixes that could be considered include plantain and rape, fescues and a summer brassica or a chicory, plantain, red clover mix.
While there are added costs to establishing mixes, they might eliminate the need to buy supplementary feed.