Key points
- Cover crops are commonly used in Queensland to cover bare soil and improve fallow efficiency
- New research is evaluating the option of growing a cover crop as a companion crop with chickpeas to ensure the soil is not left bare
Companion cropping is under evaluation as an alternative to cover crops to protect the soil after a chickpea crop.
Chickpeas are a valuable part of the Queensland cropping system, but they leave the soil quite bare. Bare soil reduces fallow efficiency – the amount of fallow rainfall captured for use by the next crop – which is a problem in areas that rely on stored soil water for yield.
Recent Queensland Department of Agriculture and Fisheries (DAF) research has shown that cover crops improve ground cover and soil water available for the next crop, prompting the question: is there merit in growing a cover crop such as wheat as a companion crop with chickpeas?
Companion crops are not new and are common in home gardens, for instance, growing marigolds to reduce tomato pests. What is novel is doing this on a broadacre scale and with mechanically harvested crops.
Investment by GRDC and DAF has enabled the DAF team to investigate the value of companion cropping of chickpeas and cereals for improved crop water use efficiency and fallow efficiency. Consultation with local growers and agronomists informed the choice of treatments that were planted at Emerald and Goondiwindi.
The real challenge is working out how to grow these two crops so that the more-competitive wheat does not significantly impact on chickpea yield.
Companion trial
The Goondiwindi trial (Table 1) demonstrated that the combined yield of the companion crops added up to the equivalent of the respective monoculture crops, had they been grown alone.
Table 1: Harvested grain yield of the crops grown at Goondiwindi as kilogram per hectare for monoculture controls and percentage of the controls for mixed treatments. Treatments with different letters had a significantly different grain yield to other treatments in that crop only (p = 0.05). Analysis was not completed across crop type, or for combined yields.
Wheat | Chickpea | Combined yield | |
|---|---|---|---|
Control (wheat or chickpea monoculture) | 2160 a | 1571 a | 100.0% |
Chickpea/wheat, alternate rows | 56.3% b | 30.4% c | 86.6% |
Chickpea/wheat, mixed within rows, 50:50 | 86.7% a | 6.6% d | 93.4% |
Chickpea/wheat, mixed within rows, 67:33 | 69.8 % b | 27.7% c | 97.5% |
Chickpea/wheat, narrow row, spray out chickpea | 87.4% a | 87.4% | |
Chickpea/wheat, narrow row, spray out wheat | 10.8% c | 10.8% | |
LSD (p=0.05) | 295 = 13.7% | 214 = 13.6% |
Source: Andrew Erbacher.
This said, and as expected, grain yields confirmed that wheat had a competitive advantage over chickpeas.
This was most evident in the chickpea/wheat 50:50 mix and two spray-out treatments, where the wheat population established was high enough to limit the chickpea yield to just 10 per cent of the monoculture chickpea.
Wheat and chickpeas were sprayed out on the same date, which was the first flower of the chickpea and, coincidently, flag leaf of the wheat. Spraying out the wheat or chickpeas at this stage meant the remaining crop produced the same yield as it achieved when both crops were harvested in the 50:50 mix, but without the benefit of the matching yield from the terminated crop. That said, a yield penalty is not unexpected in an environment where crops frequently rely on stored water to set grain.
Separating wheat and chickpeas into alternate rows increased chickpea yield from 10 per cent to 30 per cent of the monoculture chickpea, but at the expense of wheat yield.
Increasing the population of chickpeas relative to wheat (a 67:33 mix based on best practice populations of 25 chickpea plants per square metre and 100 wheat plants/m2) had the same effect.
The Emerald trial, which evaluated early or late sowing times and different row spacings for wheat and chickpeas, showed similar trends but was not analysed in time for this publication.
While being careful not to draw strong conclusions from only one season’s data, this does show that it is possible to grow companion crops in Queensland on stored soil water without an overall yield penalty.
More work is required to determine the most-appropriate crop mixes and configurations.
The primary objective of the companion crop was to increase fallow efficiency after chickpeas, increasing the yield potential of the next crop.
For this reason, sites have been maintained over the summer with cover crops grown after chickpeas. In 2022, the sites will be soil sampled for water and nitrogen, then planted to a common winter crop to measure whether companion cropping has provided any residual benefits to this next crop.
More information: Andrew Erbacher, 0475 814 432, andrew.erbacher@daf.qld.gov.au