Management options for unsown paddocks
04 Aug 2021
By Rohan Leach, Regional Ag Landcare Facilitator
**Please note all prices and gross margins are indicative only and should only be used as a guide**
2021 has been another interesting year with a wet summer, bone-dry autumn and now very soggy winter. While it certainly beats the alternative we’ve been faced with the last few years, it presents us with some different challenges to try and meet. Driving around the Central West (CW) the past few weeks, I have noticed that there is more than a few paddocks that haven’t been sown due to waterlogged country. So let’s look at what our options are and more importantly, do the numbers on each option.
- Late sown winter crop
I’ll preface this option by saying that in my experience as an agronomist, I haven’t seen a worthwhile crop sown in August in the CW. Later sown species like barley or chickpeas are typically the only option for a late sowing, while some producers may choose to put in forage cereals for a hay option. In this situation, sowing rates must be increased by 30-40% to compensate for the reduced tillering of cereals due to seasonal conditions. But again, the end of July was probably the close of this window. Even east of the Newell, I would be advising against sowing this late. Crops sown in late winter will be maturing during hot, dry weather which will reduce yield and grain quality due to heat stress.
Optimistically, we would be looking at yields of around 1-1.5 tonnes per hectare (ha) for crops sown at this date. As can be seen in Table 1, if this were the case then we are barely covering planting and harvesting costs. If the paddocks are bare, due to cultivation or burning, and you want to restore some groundcover, then sowing crop may be an option in this instance. While the crop yields will be significantly lower than a barley crop sown in May or June, the critically important ground cover will be restored.
Table 1: Late sown winter crop – Barley yielding @ 1.2 t/ha @ $210/t
Pesticide, herbicide, fungicide
Harvest (stripping, grain haulage)
- Cover Crop
As mentioned above, sowing a cover crop primarily to establish ground cover on a bare paddock is an option. Additionally, using a legume crop such as field peas, vetch or faba beans, will provide nitrogen (N) fixation of around 25kg N fixed per tonne of dry matter (DM) grown. Sown in late winter a crop like this could be expected to grow between 2-3 t of DM, fixing around 50-75kg of N per ha.
To stop the majority of this fixed N from going into seed, the legume crop is sprayed out during flowering to stop the crops development into reproduction (i.e. setting seed). This is called a “brown manure” crop and is a good option when problem or herbicide resistant weeds are making an impact in a paddock. While providing ground cover and storing N, as can be seen in Table 2, it is still an expensive option, even with urea at expensive prices (e.g. $900 per tonne) currently. However the benefit to the subsequent crop in groundcover, available N and weed control cannot be understated.
Table 2: Late sown legume cover crop - fixing 62kg N @ $900/t for urea
(urea** at $900/t
or $2.42/kg N)
*Including contract spray rates of ~$15/ha
** Urea is 46% N
- Long Fallow
A long fallow is typically used to store soil moisture and soil N in more marginal cropping systems and is a risk reduction tool (Cann & Hunt, 2018). However it could be used this year by producers, dependent on their situation. A long fallow for next year’s winter crop provides similar benefits as a cover crop but is a lower cost option. Crop stubbles, ideally, will have been conserved as reduced ground cover for long periods increases the risk of soil erosion.
The efficacy of a long fallow is dependent mainly on soil type. Clay soils will hold onto stored soil moisture more readily during a long fallow, when compared with light, sandy soils.
In terms of costs, a fallow spray at the end of spring, to stop weed seed set, is typically all that is needed in the CW. However, in herbicide resistant weed populations, a double-knock herbicide strategy may need to be employed. For around $30/ha per pass (including contract spray rates), long fallowed paddocks will likely yield more than continuously cropped paddocks, with yield increases of 60-80% observed on long fallows (Cann & Hunt, 2018), albeit in lower yielding situations.
- Summer Crop - Grazing
Another option is to give up on a winter solution and start preparing the paddock for a summer crop. As the risk is too high for most producers in the CW for a summer grain crop, this article will look primarily at grazing sorghum. This isn’t to rule out summer grain crops as an option for you, however the different market factors and crop types make this option too big to look at here.
In a recent study, conducted by McMaster, Stevenson & Strahorn (2020) at sites in Parkes and Canowindra during the summer of 2018/2019, forage sorghum proved to be very profitable for grazing enterprises. This was despite the dry conditions that summer, with well-below long term average rainfall recorded.
High dry matter (DM) yields of between 2.8-10.8 tonne were observed at Canowindra (Table 3) and at the drier site at Parkes (Table 4), DM yields of 2.1 t/ha. Even in the dry situation at Parkes, 234kg of lamb liveweight gain potential was calculated per hectare. This could gross growers over $900/ha with current lamb prices (~$4/kg liveweight) and makes a summer grazing option financially attractive.
Table 3: Cover crop feed quality results and potential lamb production results – Canowindra
Source: McMaster et al. (2020)
Another facet this study took into account was the impact of a summer grazing crop on the subsequent 2019 wheat crop. It may come as no surprise that this summer grazing crop came at the cost of a winter grain crop in 2019 at Parkes. A reduction from a summer fallow yielding 0.77t/ha to the forage sorghum treatment only yielding 0.07 t/ha, highlights the cost of this summer feed. In the higher rainfall situation at Canowindra (which may be argued to be a more average year for the CW), the summer fallow treatment yielded 2.93t/ha for the subsequent wheat crop. The forage sorghum treatment recorded a significantly reduced yield of 1.13t/ha.
Table 4: Cover crop feed quality results and potential lamb production results – Parkes.
Source: McMaster et al. (2020)
The conclusion for this option is that you can’t have your cake and eat it too! You will likely have a good grazing crop over summer at the cost of a good winter crop next year. Additionally, this does not take into account paddock sizes or a producer’s ability to source and access livestock.
While there are many options available to producers, each individual’s risk profile and capacity to undertake these options is different. A long fallow will typically be your lowest risk option. This allows you to cut your losses and hope for an early sowing opportunity next year to try and regain some of the lost opportunity observed this year. A summer grazing crop will probably be your highest risk option however it provides you an opportunity to capitalise on what will likely be high soil moisture in spring. If you have light soils that may not carry stored soil moisture over until next autumn, this may be your best option.
The answer may lie in farmers walking a fine balance between utilising a number of these options. For more specific advice please contact your trusted advisor, agronomist or give me or one of our LLS Ag Advisory team a call.
Rohan Leach | 0417 021 795 | firstname.lastname@example.org
Cann D. & Hunt J. (2018) ‘Long fallows maintain whole-farm profit and reduce risk in the Mallee’. Grains Research and Development Corporation Research Update. Accessed from: https://grdc.com.au/resources-and-publications/grdc-update-papers/tab-content/grdc-update-papers/2018/02/long-fallows-maintain-whole-farm-profit-and-reduce-risk-in-the-mallee
McMaster C., Stevenson A. & Strahorn S. (2020) ‘Summer cover crops in short fallow - do they have a place in central NSW?’ NSW Department of Primary Industries, Orange. Accessed from: https://grdc.com.au/resources-and-publications/grdc-update-papers/tab-content/grdc-update-papers/2020/02/summer-cover-crops-in-short-fallow-do-they-have-a-place-in-central-nsw
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