Rotational fit for sunflower
Benefits and opportunities
Sunflower is an economically attractive summer crop that regularly achieves excellent gross margins per hectare.
Suited to both rainfed and irrigated farming systems, sunflowers offer growers dual planting windows in most regions, adding flexibility and value to cropping rotations.
Spring (early) plant sunflower is the earliest summer crop option available, ideal for following a long fallow after cereals. A summer (late) plant enables double cropping where adequate starting soil moisture is available, as well as extending the ability to plant when other summer crop windows have closed.
Sunflowers provide an effective disease break for several key pathogens present in Australian cropping systems. They are resistant to both species of root lesion nematodes and do not host the pathogens that cause crown rot in cereals, fusarium stalk rot in sorghum or ascochyta blight in chickpea.
Sunflower plants develop an extensive, fibrous root system with a large taproot that can seek soil moisture and nutrients from depths of more than 1.5 m and can ameliorate compacted layers, leaving the soil soft and friable.
Growing sunflowers can be a valuable part of an integrated weed management strategy for controlling summer grasses and feather top Rhodes grass. Herbicide groups A, C, D, J, K and L can be used in sunflower production, removing some of the reliance on glyphosate for total summer grass control.
There are very few in-crop herbicide options for broadleaf control, however when planted into clean paddocks, the uniform emergence promotes rapid inter-row shading of weeds to maximise crop competition.
Sunflowers are very sensitive to sulfonylurea (SU) and picloram residual herbicides so avoid planting into a paddock where these herbicides have been used, until the recommended plantback interval has been reached.
Sunflowers will prosper in a wide variety of soils and climatic conditions. Compared to fibrous rooted summer crops, the sunflower plant has the ability to access deep soil moisture under dry conditions. Ensure sufficient moisture is available after budding to optimise yield and oil quality.
Sunflowers require adequate nutrition yet have a significantly lower requirement for several of the major nutrients when compared to other crops. Use soil fertility test results to manage nutrient inputs to achieve optimal oil yield and quality, and maximise grain yield.
Rainfed sunflowers are most commonly sown in spring (except in Central Queensland), following a long fallow after either wheat or barley, and are highly suited to no tillage into cereal stubble. This sequence allows broadleaf weed control in the preceding cereal crop and cereal stubble provides adequate ground cover to minimise erosion. An alternative is to plant sunflower in spring following a short fallow from sorghum.
Double cropping in the summer immediately after a winter cereal is an option in seasons where there is sufficient post-harvest rainfall to fill the soil profile going into the summer planting window.Double cropping can provide a lower cost option than mungbeans, however this practice is not recommended if stored soil moisture is limited.
In a cereal-dominant cropping sequence, sunflowers provide an excellent break for cereal diseases such as crown rot and root lesion nematodes, and an opportunity to control grass weeds.
Sunflowers should not be planted following crops such as canola and rice, which do not host arbuscular mycorrhiza (AM, formerly known as VAM), a fungi that assists in nutrient availability (particularly phosphorus). AM fungi levels can also be low after a long fallow, potentially requiring the application of phosphorus and zinc fertiliser.
An overall understanding of disease pathogens and how they affect each crop in the rotation is important so that informed decisions can be made regarding potential disease risks. It is best to avoid sowing sunflowers in close succession with other broadleaf crops due to the risk of diseases carrying over from one broadleaf crop to the next. Best practice guidelines suggest not planting sunflowers more than once in a three-year period.
Preservation of the cereal stubble layer is very important for sunflowers. Stubble from winter cereals promotes water infiltration, protects seedlings from sand blasting and provides ground cover to reduce erosion while the sunflowers are growing and after the crop is harvested.
The use of Kelly-chains for weed control is not considered best practice because the implement can disturb the stubble, increasing the rate of soil moisture loss and may contribute to soil compaction and pathogen spread.
Use a precision planter suited to minimum or no-till systems to achieve an even plant spacing and avoid double seeds and gaps. The resulting even plant stand will maximise yield through uniform head and grain size.
Sunflowers leave the soil softer and more friable than other crops and their strong tap roots can break up compacted layers.
Combined with stubble cover, no-till aids moisture retention, leading to consistently higher yielding sunflower crops. No-till also provides a wider sowing window and stores more soil water. This enables a shorter fallow with more efficient water use, less runoff and less erosion.
However, no-till can encourage the build-up of stubble borne pathogens, soil insects and mice compared to conventional land preparation. Insecticidal seed treatment is recommended when planting into zero tillage fields. Monitor mice numbers and treat if necessary.
Growing sunflowers in a no-till system relies on effective weed control in the previous crop and fallow. In no-till farming, the options for some broadleaf weed control may be limited due to the inability to effectively incorporate pre-emergent herbicides. When applying pre-emergent herbicides in high stubble situations, increase the water volume and choose herbicides suited to the stubble load present.