Grains Research and Development

Date: 29.01.2016

Making money from summer rain in the HRZ

Author: Alistair Lawson

Cam Nicholson, Grain and Graze 2 southern region coordinator with sheep grazing on wheat stubble at his Bellarine Peninsula property in Victoria.

Cam Nicholson says the grazing value from some fodder

options is considerable, with a minimal impact on yield in

subsequent winter grain crops.

While storing summer rainfall through weed control over the fallow period is vital in contributing to yield in following crops, research from the high-rainfall zone (HRZ) may suggest otherwise for areas such as southern Victoria.

In fact, there is opportunity for growers in the HRZ who have soils with a lower water-holding capacity to make more money by potentially planting a summer forage or cover crop without having any impact on the next winter crop.

Nicon Rural consultant and regional Grain & Graze coordinator Cam Nicholson says rainfall outside of the traditional growing season is a noteworthy contributor to the amount of annual rainfall in Victoria’s south-west.

Long-term analysis at Lake Bolac from December to April indicates about 25 per cent of average annual rainfall is received in those five months.

“Examination of soil moisture probe data from a Grain & Graze grazing trial at Lake Bolac conducted from late 2010 to early 2014 would suggest soil moisture is still lost from the soil surface, even with very good weed control and a reasonable amount of stubble cover,” Mr Nicholson says.

“While some of the rainfall over the December-April period may have run off, a large amount infiltrated into the soil. But by the start of the winter growing season (May 1) virtually all of the rainfall over the summer period was lost, most likely through capillary rise, which is the effect created when the suction caused by dry air at the soil surface draws soil water out of the pore spaces.”

Mr Nicholson says soils with higher clay content have greater potential to lose soil water from capillary rise than sandy, textured soils.

To see whether a summer fodder crop drains the soil profile of summer rain even more than evaporation, a lucerne stand was established to monitor soil moisture levels alongside a summer fallow. Mr Nicholson acknowledges it was an extreme comparison with lucerne being an aggressive fodder in terms of its “thirst” for moisture over summer. However, he says there were two significant observations.

  •           Established lucerne extracted more moisture than the fallow but the difference was not as great as expected. In 2010, the additional loss of moisture from lucerne was 40 millimetres, 43mm in 2011 and 21mm in 2012.
  •           The same evaporation effects occurred over summer confirming that soil moisture is lost under fallow.

“However, lucerne is a perennial and after a few years it would have a well-established root system,” Mr Nicholson says. “Most annual summer crops would not have had the chance, or have the plant characteristics, to create such a root system. Therefore, the additional loss may not be as great in annual-sown summer fodders as lucerne.”

In order to dig deeper into the effects annual-sown summer crops might have on soil moisture, eight trials were sown across sites at Werneth, Winchelsea and Skipton in the 2010-11 and 2011-12 seasons. Four of the trials were harvested for grain, three for fodder and one for fodder and grain. All trials were followed by a winter crop except for one which was continuously grazed.

It found that there was no yield penalty by growing a fodder crop in the previous summer for any winter crop (table 1).

 

Table 1: Yield of a summer fodder crop and following winter crop (2010-11 and 2011-12)

 Year Location
Summer crop
Summer crop yield (t/ha)
Winter crop
Winter crop yield (t/ha)
 2010-11 Werneth Sunflowers 0.46  Barley 1.84
Unsown 0
1.85
      NS (not significant)
Werneth Sorghum
Not harvested
 Barley 2.11
Unsown
0
2.46
       NS
2011-12
Winchelsea Forage sorghum (cv Feedex)
16.1 DSE/ha across 33ha (240 weaner cattle for 10 weeks, 160 cows for 1 week)
Grazing wheat
Wheat grazed over winter - no yield available
Unsown
0
 
      N/A
Skipton
Fodder rape (cv Winfred)
7.4 DSE/ha across 65ha (1500 lambs for 60 days)
Wheat
7.2
Unsown
0
7.14
      NS
Skipton
Dual purpose rape (cv Taurus)
4.7 DSE/ha across 65ha (1500 lambs for 38 days)
Canola (Taurus)
0.64 (spring-sown canola struggled under high weed pressure)
Unsown
0
  0
      N/A
Werneth
Corn
0.39
Wheat
Trial harvested by mistake
Unsown 0
      N/A
Skipton
Peas
0.3
Canola
1.48
Unsown
0 1.53
      NS
Skipton
Maize
1
Wheat
2.69
Unsown
0
2.5
      NS

 

“If the summer crops sown for grain are excluded, the grazing value from some fodder options are considerable,” Mr Nicholson says.

“In regard to soil moisture, in five of the eight trials soil moisture was higher in the summer crop treatments than the fallow – by up to 35mm – and in the three trials where soil moisture was lower in the fodder crop the deficit only reached 16mm.”

Soil nitrogen at the start of the winter growing season was reduced following a summer crop but subsequent grain yield was not affected.

“This defies intuition,” Mr Nicholson says. “However the yields of the winter crops were not large and the grain protein was similar, suggesting there was sufficient soil nitrogen to meet crop requirements, especially after the in-crop application of nitrogen. Further, many of the fodders were grazed, meaning much of the dry matter would have been returned to the soil in dung and urine.  This probably wasn’t picked up in the initial deep N testing but may become available later in the winter cropping period.

“The weed response was also different to expectations.  It was assumed summer crops grown for grain would compete against weeds and therefore reduce weeds.  Instead weed reduction was only measured in the summer crops used for fodder and grazed.”

More information

Cam Nicholson, 0417 311 098, cam@niconrural.com.au

GRDC Spring-Sown Winter Canola Fact Sheet

GRDC Project Code SFS000018

Region South