Strategies: Deep, but how meaningful? An approach to difficult winter crop conditions in 1999 by Peter Ridge
The winter growing season around Dalby in 1999 was much drier than normal with winter (April-September) rainfall only 58 per cent of the long-term average. In addition, the planting rains for winter crop were delayed until the last few days of June, and even then the rain was only just sufficient (25-30 mm) to plant with confidence.
The only cause for optimism was the large reserves of soil water accumulated under fallows through the very wet 1998-99 season. These reserves of subsoil water, rather than the seasonal outlook, drove the decision to opportunity-crop chickpeas into sorghum stubbles.
Some chickpeas were planted deep into moisture in May, a full six weeks before the planting rains eventuated at the end of June. These crops established well and were always much more vigorous than their later-planted (early July) counterparts.
However, in the end there was no yield advantage from early deep planting — soil water seems to have been responsible for success of both crops, which yielded 1.3-1.5 t/ha.
This was a highly profitable result, generating a gross margin for the one crop of $290/ha (1.4 t/ha @ $350 less $200/ha direct costs) within a six-month period. Adding in the preceding sorghum crop, gross margin $300/ha (5 t/ha @ $100 on-farm, less $200/ha costs), this is equivalent to an annual gross margin of $590/ha.
By way of an in-season comparison, another crop of chickpeas planted on summer fallow yielded about 2 t/ha to generate a gross margin of $450/ha (2 t/ha @ $350/t less $250/ha direct costs) in twelve months.
The dry conditions and seed bed through May and June also prompted some dry planting of wheat. The justification for this was that there would be less pressure on the planting unit once the planting rains materialised if a significant proportion of the crop had already been planted dry. Crop establishment after dry planting was quite adequate once it rained in late June, and typically these crops went on to yield as well as their later-planted (into moisture) counterparts. Wheat yields from dry planting were about 3.5 t/ha.
While there were no yield gains from either deep moisture-seeking planting of chickpeas or dry planting of wheat, these strategies did reduce the amount of crop needing to be planted once it did rain.
Contact: Mr Peter Ridge 07 4639 4422