In big paddocks a tweak can make all the difference

Farmer-owned agribusiness Agricultural Marketing and Production Systems (AMPS) in the past two seasons has conducted research at north west NSW locations with results highlighting big in-paddock elevation differences and different yield outcomes within a crop.

AMPS research agronomist Matt Gardner and colleagues conduct the joint AMPS and GRDC funded elevation by planting date research round Spring Ridge (Liverpool Plains) and Moree.

Mr Gardner notes their research highlights that of all the growing tools farmers have for potentially increasing yield and profit, planting date can give the greatest yield increase, but doesn’t come without risk.

However, using temperature differences with elevation within a paddock or across a landscape, may allow farmers to plant earlier while minimising some of the frost risk associated with early planting.

An example of temperature variation over a paddock is illustrated in data collected from two research sites in the one paddock at Spring Ridge.

Elevation at the top of the slope site was 353 metres above sea level (ASL) and 305 meters at the bottom of the slope, a difference of 46 metres.

Between May 1, 2015, and October 12, 2015, minimum temperature differences were 3.5 degrees Celsius higher at the top site compared to the bottom site.

Average maximum temperatures were similar with the top site being on average 0.4 degrees warmer. 

But the top elevation site only recorded 16 frosts (less than 0C) compared to 54 frosts at the lower site. Total frost hours were 31 compared to 243 hours at the lower site, which represents two very different frost risk profiles within the same paddock.

Mr Gardner reports these temperature and frost differences impacted on flowering date of a range of varieties (from slow maturing to quick maturing) sown at each site over three different sowing dates from late April to early June. Varieties assessed were (from slowest to fastest) Eaglehawk, Gregory, Lancer, Suntop, Spitfire and Dart.

Days to flower from a April 30 sowing was over all varieties 132 at the top of slope compared to 146 at the bottom of the slope, a difference of 14 days.

From the May 19 sowing days to flowering were 123 verses 138 and the June 13 sowing 118 verses 122.

Temperature and frost differences contributed to vastly different yield patterns for the various varieties and Matt Gardner said largely reflected maturity differences.

Dart – a very quick maturing variety - from the April 30 sowing yielded 6.2 tonnes per hectare from the elevated trial site but only 1.2t/ha from the bottom site. 

Suntop - normally regarded as an early to mid-May onwards sowing variety - showed its versatility yielding high in both the top and bottom of slope in the late April sowings. Yields were respectively 7.3 and 6.8t/ha.

Spitfire, a faster maturing variety, yielded high in the late April sowing on the higher country (6.4t/ha) but relatively poorly on the lower site (2.6t/ha).

Slower maturing varieties like Lancer Gregory yielded around the same at both top and low elevation sites and with a hot dry spring did not yield up to varieties with faster maturity.

Early sowing with appropriate varieties at both top and lower elevated sites tended to yield better than later sowings.

These finding support other detailed AMPS research at many sites.

Matt Gardner feels elevation differences offer an opportunity for earlier planting with relatively moderate frost risk.

He also points out while elevation is responsible for variation in temperatures other landscape aspects like drainage points and tree lines can all combine to influence frost risk.