Sub soil moisture level is one key aspect to consider if planning a summer crop, especially in non-traditional summer crop areas.
Soil type is also important, so is assessing possible herbicide residual issues, how a summer crop may affect future farming programs, likely weed issues, soil fertility, pests, diseases and possible fodder value if a grain crop fails.
Several farmers as far south as Victoria over the years, have successfully grown dryland summer crops in non-traditional summer cropping areas.
Most will tell you to forget it if you don't have a near full soil water profile and only grow it on soils that can store good levels of plant available soil water (PAW). So, for many farmers summer cropping is only a consideration if a series of above average rain events occur in time for summer crop sowing.
Some soils, like a deep clay loam, can store 200 millimetres of PAW to 2 metres depth. In contrast a sandy loam surface over light clay, may only store 100mm PAW.
Stored soil moisture is essential in most traditional summer cropping areas, let alone in areas with less reliable summer rain, to get them through typical hot and dry summer growing periods.
One simple tool to assist with soil moisture levels is the Fawcett push probe (see dpi.nsw.gov.au/agriculture/irrigation/irrigation/scheduling/moisture-probe).
It can be easily made with care, can determine soil water depth and ease of pushing helps assess if soil is partially or near full of stored soil water. Far more sophisticated soil monitors are available and now commonly used by farmers.
Apps have also been designed to assess likely PAW. The Soilwater app is an example and estimates likely PAW provided you accurately enter data such as soil type and depth, fallow commencement, stubble cover and location to nearest BOM weather station (or enter own rainfall data). Soilwater assumes fallow management has been of a high standard.
Risk of sowing on limited PAW can be checked via the CliMate app that assesses probability of receiving a given amount of rain in the growing season. Information such as growing time and nearest BOM recording centre provides estimates based on past rainfall records.
Check herbicide labels for products used in previous crops or fallows, as some could have residual activity that may adversely impact on some summer crops. Residual soil activity of some herbicides can be prolonged in extended dry periods.
Table 2 in the NSW DPI's latest Weed Control in Winter Crops booklet provides useful herbicide residual activity, including in relation to several summer crops. Fallow herbicide drift can also be a big risk factor.
Last year via this column regular summer croppers, Mark and Katrina Swift of Kebby and Watson Tichborne, highlighted the need to carefully assess plans for summer crops. They stressed that summer cropping required a business plan that included regular monitoring (that can clash with times, such as traditional holidays) for issues like pest control.
Broadleaf crops like mung beans especially require monitoring twice a week with prompt control if pest numbers are above threshold levels.
Mark Swift stressed that summer crops need to be considered as an important part of the rotation, properly budgeted for, including cash flow implications, work requirements and impact on future crops such as sequencing back to winter crops.
Agronomy issues with summer cropping include row configuration and sowing rate (plant population). For example, NSW DPI research, funded by GRDC noted that for grain sorghum solid row configuration, 1m spacing, generally gave the greatest return in above average seasons.
In a good season, the advantage over skip row configuration can be as high as 1 tonne a hectare. If yields are low, the difference between row configuration is much smaller.
Research also showed that sorghum established populations from 30,000 to 50,000/ha yielded similarly when yields were between 2-4t/ha and only in very low yield situations (about 1t/ha) 15,000 to 30,000 plants/ha yielded better. Hybrids with at least a moderate level of tillering and mid-season maturity commonly yielded best.
Next week: Series of canola growing seminars coming.
- Bob Freebairn is an agricultural consultant based at Coonabarabran. Email robert.freebairn@bigpond.com or contact (0428) 752 149.
