Long term no-till farming systems

Improving the quality of no-till

Neil Cordingley, WANTFA Project Manager

The aim of this GRDC-funded trial is to determine the long term benefits of the key components of conservation agriculture—crop residue retention, diverse rotations, minimal soil disturbance and reduced compaction (controlled traffic)—in Western Australian cropping systems. Aspects that are considered include soil carbon sequestration, diseases, insects, weeds, and the water balance, as well as crop yield and profitability. (This project has been funded for a further three years)

The 2013 harvest completed seven years of cropping the long term no-till systems project which commenced in July 2006. The seventh year completed the first phase of the third three year rotation which started in 2013, and the project is now into the eighth year.

In 2010 the plots in treatments 1 and 2 were split for high residue (all residue retained – spread behind harvester) and low residue (residue windrowed behind harvester and burned) and both splits in treatment 4 were low residue (i.e. windrow burnt).  This will provide larger differences in residue levels between treatments and help with weed control. There are also differences within the subplots in residue spread with higher residue levels directly behind the header and lower levels between the header runs. Sampling has been targeted to capture any effects this residue spread may have.

In 2013 the max profit treatment 4 was changed to cereal/cereal/fallow and also included a shallow tillage in half the plot; these were aimed at further reducing crop residue levels for some of the treatments, which will provide greater contrasts between treatments. The use of fallow and tillage are increasing in the wheatbelt so these treatments should provide important longer-term information on the impacts on soil health and carbon. The combination of occasional fallow (once every three years), windrow burning and tillage in treatment 4 is expected to produce the lowest levels of crop residue cover and soil carbon.

Treatment 3 will continue unchanged with the permanent pasture and continuous cereal controls. The residue differences will provide more definitive information to test the hypothesis that high residue levels are required for high quality no-till cropping systems.

Table 1. The long term no-till project rotations 2013 to 2015.

Table 2. Monthly rainfall for 2013 and 2014 at the Cunderdin site (GSR = Apr to Oct rainfall)

The 2013 season

In 2013 the Cunderdin site had 303 mm total (average 356 mm) and 229 mm growing season rainfall (average 278 mm). There was some significant summer rainfall with 30 mm in both January and March but April only received 4 mm which is well below average. Seeding commenced at the end of April with the canola dry seeded and the wheat, barley and chickpeas seeded in May into moisture (with May receiving around average rainfall of 42 mm). There was rain straight after seeding the wheat which caused trifluralin damage in the plots seeded using the disc and it was decided to re-seed these plots which occurred in early June. Rainfall in June was very low with only 3.6 mm and the dry period continued into early July causing patchy and slow establishment, particularly in the re-seeded wheat. After June and early July average to above average rainfall was recorded with September receiving above average rainfall of 70 mm. The good finishing rains meant yields were good with the re-seeded plots yielding similarly to the wheat that wasn’t re-seeded. The wheat yielded on average 2.6 t/ha, the barley 3.6 t/ha, canola 1.5 t/ha and the chickpeas 1.7 t/ha. The high residue plots yielded slightly more than the windrow burnt plots although this was not significant apart from the barley which yielded 4.1 t/ha in treatment 1 (high residue} compared to 3 t/ha in treatment 4 (low residue).

Figure 1. Grain yield (t/ha) at Cunderdin in 2013 (error bars are ±SE of the mean).

The 2014 season

The 2014 season is the eighth crop and the second of the third three year rotation. The site received average total rainfall of 358 mm and above average growing season rainfall of 321 mm. The above average growing season rainfall was mainly due to above average rainfall in April, May and October. There was a very dry start to the year with only around 8 mm rainfall up to April. Although April received above average rainfall most of this came at the end of the month with 50 mm on 27 April. Seeding commenced at the beginning of May with the IH30RR canola and the wheat, barley and chickpeas seeded from mid to late May. May also had above average rainfall with 30 mm in the second week after the canola was seeded then another 30 mm over the last seven days of May. The above average rainfall in April and May meant all the crops had good establishment, although after the below average June rainfall the wheat after canola and wheat after fallow looked more advanced with greater biomass which continued through to harvest.

The wheat on wheat plots in treatment 1 and 3 looked to have lower biomass and higher disease and weed levels. The canola had good establishment and trifluralin at seeding followed by the two applications of Roundup® gave excellent weed control. The chickpeas didn’t perform as well this season with high weed numbers and Ascochyta blight reducing plant and pod numbers. The trial has been harvested with both hand cuts to assess yield and quality and a commercial header to provide the different residue management to the treatments.

The 2015 season will be the ninth and final crop in this rotation. The differences in residue management since 2010 and the introduction of tillage in 2013 have started to provide differences between treatments. Data collection will continue with collection of ground cover, residue and crop biomass, establishment, soil compaction, weeds, disease, yield, quality and input costs along with statistical and economic analysis. A comprehensive soil analysis will be completed in 2016 to assess the changes in the soil. The aim will be to continue the trial for a further three years as treatment differences are beginning to occur and it is still a relatively short time since the residue management changes occurred in 2010 and the introduction of tillage in 2013.

Acknowledgments

WANTFA would like to thank the GRDC for their support, the Cunderdin Agricultural College for their support, assistance and allowing the trials on their land, Bayer for providing the canola seed and Trimble for providing the autosteer correction signal.