Have you go the green light for planting?
Planting is one of the most important operations on the farm. It sets the standard for the entire season and helps pave the way towards achieving optimum crop growth, and ultimately yield.
HAVE YOU GOT THE GREEN LIGHT FOR COTTON PLANTING THIS SEASON?
CSD have developed a traffic light system to quickly gauge the conditions at planting. There are some key considerations that will help ensure it’s a once only task:
Ο Is soil temperature at 10cm depth above 14°C at 8am? (AEST)
Ο Is forecast average temperatures for the week following planting on a rising plane?
- If you cannot give a green tick to at least one of these statements, then planting conditions are definitely unsuitable – STOP!
- If you can give a green tick to only one of these statements – BE CAUTIOUS. Adjustments may need to be made.
- If you can give both statements a green tick – Let’s GO!
To check your soil temperature and 7-day forecast, CSD members can access the FastStart™ Soil Temperature Network. The FastStart Soil Temperature Network consists of a network of approximately 50 automatic weather stations located across cotton production areas in New South Wales, Queensland, the Northern Territory
and Western Australia – www.csd.net.au/soil-temperature.
These sensors are a real-time measure of the soil temperature at 10cm and can be used as a guide to whether conditions are suitable for planting cotton.
This FastStart Soil Temperature Network decision tool uses the accumulated day degrees over a 7-day forecast, whilst also taking into account the influence of cold shock, to give you a figure out of 100. This is then divided into four categories:
| < 30 DD | Very Poor | |
| < 60 DD | Poor / Caution | Warrants caution as a delay in emergence is likely and may impact upon germination percentages and/or exacerbate seedling disease or soil insect attack. Management intervention is encouraged |
| 61 – 80 DD | Adequate | Considered adequate however ensure other planting parameters and conditions are ideal. Cotton will likely take greater than 7 days to emerge. |
| > 81 DD | Good | In excess of 81 DD is considered as the requirement for ideal germination and emergence. |
Table 1: FastStart Soil Temperature Network scoring.
As the data in Table 1 shows, a very poor category reading would likely incur significant number of cold shock events. The poor/caution category is marginal planting conditions and if planting is to be conducted under this forecast some adjustments to the planting operation will be needed. The adequate category occurs when there is a good temperature forecast and cold shock events are minimal. Obviously, planting can occur outside the good conditions, however management intervention such as increasing planting rate to ensure an adequate and even plant stand should be considered.
This study highlights the importance of planting cotton into optimal conditions, with a soil temperature above 14 degrees Celsius and a rising forecast of temperature over the next seven days (i.e. a green traffic light).
PLANTING RATE
A uniformly spaced plant stand is more critical than the actual number of plants per metre, although there are more disadvantages with having a plant stand which is too low than too high. Depending on season length, this can be critical.
When determining the optimal plant population, it is important to consider:
- Soil type and conditions.
- Irrigated or dryland production system.
- Soil water holding capacity – planting into moisture, watering up or reirrigating.
- Long term average yields – based on area with plant population rates.
- Germination rates.
- Seedling mortality – disease and insects.
- Rainfall and temperature (soil temperature and forecast air temperature).
- Row spacing.
CSD recommends a planting rate of 8-12 plants per metre established for irrigated conditions in Central and Northern regions; and 12 plants per metre established in Southern regions.
The recommended planting rate for dryland cotton is 6 to 8 plants per metre established.
CSD have conducted numerous plant population trials in recent years to look at the optimum plant stand for maximum yield. Across these trials, a plant population above 8 plants/m has consistently been shown that it does not result in a significantly different final yield (see Figure 2).
Gaps can limit yield potential of the crop, which can lead to uneven maturity of plants and difficulties in managing fields for weeds, insects, growth regulators, defoliants, root cutting and picking. These gaps are further exaggerated in wider planting row configurations where neighbouring rows may be too distant for compensation.
CSD have developed a Cotton Planting Rate Calculator which combines many years of trial work to generate a proposed planting rate to achieve the established plant population desired. The calculator takes into account many of the factors which influence the establishment of cotton, and starts with the final established plant stand as the target.
Figure 2: Summary of CSD plant population trials across various regions.
FIELD CONDITIONS
It’s important to have the seedbed in the best possible shape at planting in order to achieve a more uniform establishment. Factors that contribute to the field condition are:
- Uniformity of soil across the field.
- Size of the soil particles.
- Stubble cover across the field.
- Breakdown of stubble specifically in the planting line.
- Weeds being present in the planting line.
CSD has developed a field ranking score from 1 to 5, with 1 being the ideal for establishment and a 5 likely to result in a poorer establishment.
FIELD SCORE 1
Stubble fully broken down, usually cereal not cotton stubble. Firm seedbed which will support the planter unit. Beds have been rolled or shaped. Weed free. Seed zone free of soil particle size > 2 cm.
FIELD SCORE 2
Similar to field score 1 but presence of larger soil particles (up to 2 to 3 cm).
FIELD SCORE 3
Presence of soil particles up to 3 to 5 cm. Some stubble mixed into seed zone. The odd weed and the bed not as firm as 1 and 2, slightly sinking when pressure is applied
to the bed.
FIELD SCORE 4
Presence of medium to large soil particles, up to 5 to 8 cm. Increasing amount of trash. No firmness to bed. Your feet start to sink when walking on bed. Starting to see cotton volunteers/fuzzy seed in back-to-back cotton situations.
FIELD SCORE 5
Presence of large particles up to 10 to 15 cm. Large remnants of past crop residues. Weeds present. No soil structure within the bed. A lot of air gaps. Beds sink away when walking on them. Remnants of cotton butts still in planter row, volunteers and high fuzzy seed levels in back-to-back cotton situations.
PLANTER SPEED
One of the keys to plant stand uniformity is planter speed. The aim should be to plant with precision, not speed.
CSD has conducted planter speed trials to assess the effect on establishment of commercial planters at varying speeds. Sites varied in soil type, moisture, rotations, disease and insect pressure and weather conditions, with locations from Southern NSW to Central Queensland. The only variable in each trial was speed.
Each area had its own different seed drop (seed planting rate) – Figure 3 illustrates the percentage loss from the initial seed drop. For example, if the treatment was planted at 10 seeds/m and only 5 plants established for 10 km/hour, this would represent 50 per cent establishment for 10 km/hour.
Results from the trials showed an ideal plant speed of around 8 to 10 km/hour. The average population decreased when the planter sped up past 10 km/hour, while the percentage increased from 4 km/hour to 8 km/hour.
Figure 3: Effect of planter speed on establishment percentage.
PLANTER DEPTH
The depth you want your seed depends on the method of establishment and soil conditions. Many people use the ‘knuckle method’ as a quick and easy measurement
tool in the field (Figure 4).
| Establishment method | Ideal depth |
| Planting into moisture (rain or pre-irrigated) | 2.5 and 4.5 cm (1 to 1.5 knuckles) |
| Planting dry and watering up | 2.5 cm (1 knuckle) |
Table 2: Generic recommendation for planting depth based on establishment method.
When planting into moisture, some dry soil above the seed slot is useful to prevent moisture loss from around the seed. If there is too much however, a rainfall event after planting will turn this dry soil into wet soil and increase the difficulty for young seedlings pushing through. Check the consistency of the soil above the seed. If the pressure from the press wheels on the planter is set too high, you can get a compacted zone above the seed and the young seedling will have a tough time emerging.
It is important not to plant too deep, as research has show that planting at depths of more than 5cm can compromise establishment and increase the threat of soil borne pests and diseases as well as depleting the seed of stored energy.
Conversely, planting too shallow can lead to the soil drying back before imbibition is complete and can also increase the risk of capping as the emerging seedling passes through an insufficient amount of soil to brush the seed coat off. However, planting too deep also has risks with greater time to emergence increasing the threat of soil borne pests and diseases as well as depleting the seed of stored energy.
Figure 4 (right): The ‘knuckle method’ of quickly measuring depth in the field.
© Cotton Seed Distributors Ltd 2022. General guide only; not comprehensive or specific technical advice. Circumstances vary from farm to farm. To the fullest extent permitted by law, CSD expressly disclaims all liability for any loss or damage arising from reliance upon any information, statement or opinion in this document or from any errors or omissions in this document. Roundup Ready Flex®, Roundup Ready®, Bollgard II® and Bollgard® 3 are registered trademarks of Monsanto Technologies LLC, used under licence by Monsanto Australia Ltd. Insect control technology incorporated into these seeds is commercialised under a licence from Syngenta Crop Protection AG. Sicot, Sicala, Siokra and Sipima cotton varieties are a result of a joint venture research program, Cotton Breeding Australia, conducted by CSIRO and Cotton Seed Distributors Ltd (CSD). CSD is a partner in the CottonInfo joint venture, in partnership with Cotton Research Development Corporation and Cotton Australia.