Introduction

The objective of ICI Rural Division is to be a supplier of innovative crop care products and product use programmes aimed at improving farmer profitability. The benefits which ICI products and programmes offer must be understood by the farming community.

In general the appropriate use of our products has facilitated change in farming practice, e.g. minimum tillage, or suited change initiated by other causes, e.g. the increase in legume break crops. Clearly change is a relatively slow process and in extension terms can be broken down into a number of stages referred to as awareness, interest, information, reference, testing, adoption and reward.

Critical to the adoption of a change in practice is a comprehensive set of data and a network of referees which substantiates the benefits that a particular change offers. In the late 70s, ICI recognised that to be successful in introducing change it must lead its customer throughout each stage to adoption. Since 1979, ICI has employed a number of techniques including Crop Production Groups which were introduced in 1984.

The State Of The Art

In terms of grain growing efficiency it has been demonstrated by researchers that significant opportunity exists to improve water use efficiency by cereal crops. Estimates vary but in general terms every mm of growing season rainfall should result in 10-20 kg/ha of grain. For example, if the growing season rainfall in the Rutherglen area is 400 mm then a yield of 4 t/ha is a conservative yield expectation.

Measurement of actual yields indicates that they represent between one-third and one-half of the potential. A number of key elements have been identified as important in achieving potential yields:

• sowing on time using the right varieties

• maximising soil moisture at sowing

• controlling in-crop weeds

• using the appropriate fertiliser programme, particularly nitrogen

• using the correct sowing depth and rates

• removing the obstacle of root disease

• reducing the incidence of cereal cyst nematode

The reality of seasonal variability ensures that it will always be difficult to achieve each key element but a fuller understanding and a planned approach can help.

The Basic Principles

There are well established agronomic principles which will contribute significantly to the achievement of potential yields. The most important include:

• sowing techniques in relation to timing, seedling depth and paddock selection and preparation. Minimum tillage techniques can improve timeliness, maximise soil moisture and provide a disease break;

• the use of grass-free rotational crops to provide a disease break and in certain instances improve soil nitrogen status. Break crops include pasture;

• the choice of the right variety;

• the strategic use of crop care products to prevent seed-borne disease, control in-crop weeds and prevent insect damage.

Crop Production Group Programmes

The ICI Crop Production Groups were established as a means of allowing ICI and participating farmers to generate localised data to validate the more important agronomic principles. The Crop Production Groups have used gross margin analysis to measure the effects of varying cropping practice. The active participation by farmers in these groups has ensured a very effective learning process and generated regionally specific information. To date 1487 comprehensive paddock records have been prepared.

The Results

The results presented have been selected from the database. As such they are samples used to indicate trends. Understandably, the participating farmers did not conduct statistically valid comparisons of different cropping practices. Therefore, some caution needs to be exercised in interpreting the results. However, sufficient data now exists to provide firm guidelines for Improving cereal productivity.

Table 1. Effect of rotation on the yield and gross margin of wheat

PREVIOUS CROP	1985		1986		1987
	($/ha)	Yield	GM	Yield	GM	Yield
		(t/ha)	($/ha)	(t/ha)	($/ha)	(t/ha)
Lupins	226	3.2	216	3.8	214	3.2
Rape	165	2.4	188	3.6	198	3.2
Clover	239	3.4	185	3.3	211	3.1
Pasture	194	2.4	166	3.2	153	2.6
Peas	102	1.6*	171	3.0	163	2.5
Wheat	165	2.3	107	2.5	134	2.5
Oats	194	2.7	131	2.9	151	2.4
Fallow	130	2.1	162	2.9	130	2.2
Total Crops		355		354		182

*Limited data - Mallee only

The data presented in Table 1 shows the effect of preceding cropping history on wheat yields in 1985, 1986, 1987. The highest yields, and hence gross margins, were obtained from wheat when the preceding crop was either lupins, rape, clover or peas. The beneficial effect of these break crops is enhanced when they are grass-free.

Table 2. Effect of time of sowing on the yield of different wheat varieties.

CARISBROOK 84/87 (84 crops)

Time of Sowing		Yield t/ha)
May	early	Oxley	Matong	Millewa
	late	3.0	3.0	2.8
June	early	3.1	2.5	3.3
	late	3.0	2.1	2.9
July	early	2.7		2.1
	late	2.4
		2.1

MARNOO 84/85/86 (106 crops)

Time of Sowing		Yield (t/ha)
May	early	2.3	Millewa
	late	2.8	3.0
June	early	2.8	2.5
	late	2.6	2.1
July	early		2.0

BURRUMBUTTOCK 84-87 (102 crops)

Time of Sowing		Yield (t/ha)
May	early	Milewa	Banks	Corella	Osprey
	late	3.1	3.6	3.2	3.6
June	early	2.9	3.4	3.0	2.6
		3.2	2.0	3.8*

* limited data

Sowing date data is presented in table 2 and has been selected from crop production groups located at Carisbrook, Marnoo and Burrumbuttock. The- data clearly indicates optimal sowing dates for specific varieties and yield decline associated with delays in sowing. In these three areas yield penalties are very likely when sowing is delayed beyond early June.

Table 3. Effect of sowing method on wheat yield in 1985 (355 crops)

Method	Yield (t/ha)	Gross Margin ($/ha)
Direct drill	2.4	167
Minimum
tillage	2.4	168
Short fallow	2.4	167
Winter fallow	2.3	149

The use of minimum tillage for crop establishment has proven benefits in relation to soil conservation, extended machinery life, timeliness and flexibility. The data presented in Table 3 for 1985 indicate no yield penalty associated with the use of direct drilling or minimum tillage. Interestingly, whilst the yield from winter fallows was comparable, gross margin was lower due to costs associated with the maintenance of the fallow.

Table 4. The effect of sowing depth on plant population (207 crops)

Depth (cm)	P1ant population/m2
	Oxley (110 kg/ha)	Millewa (80 kg/ha)
2	160	90
3	208	159
4	210	173
5	168	168
6	150	150

The effect of sowing depth or planting populations has been recorded for 207 sites at Oxley and Millewa and the results are included in Table 4. In both incidences optimal seeding depth was in the range 3-5 cm.

The Conclusions

In a business sense the most appropriate measure of success is profit. The gross margin analysis for the top and bottom 25% of crops grown in 1987 (355) is presented in Table 5. There was a 2.0 t/ha difference in average yield and a $166/ha difference in gross margin. The groups had similar investments in seed and fertiliser but the higher yielding group spent more on crop care ($32/ha vs $19/ha).

Table 5. Gross margin analysis for 355 wheat crops in 1987

Average yield (t/ha)	Top 25%	Bottom 25%
Variable costs - seed	3.8	1.8
($/ha) - fertiliser	$11	$9
- crop care	$27	$26
Total variable cost ($/ha)	$32	$19
Gross margin ($/ha)	$70	$53
	$259	$93

Profit Analysis - Burrumbuttock 1987

	Average	Range
Yield (t/ha)	2.9	1.2 - 5.0
Variable costs ($/ha)	$125	$63 - $179
Gross margin ($/ha)	$137	$66 - $370
Fixed costs ($/ha)	$137	($77 - $280)
Profit ($/ha)	$0

More significant, however, is the data from the Burrumbuttock group in 1987. On average after allocating fixed costs the profit was $0/ha, but the ranges of yield and cost data contributing to the average indicate individual paddock gross margins ranging from $66/ha to $370/ha. Fixed costs cannot be allocated specifically but ranged from $77/ha to $280/ha. Imagine 5 t/ha yield and total costs (fixed variable) of $256/ha giving a profit of approximately $300/ha!

Clearly such large variation within the one region (and sometimes on the one farm) is of concern. Detailed analysis of individual paddock records indicates that all key factors determining yield need to be in place to ensure consistently high results. Failure to sow on time, for example, can negate the effect of planned rotations. However, the ICI Crop Production Groups’ results demonstrate that farmers are achieving their potential yields by understanding the important factors influencing yield and planning and managing their cropping programmes appropriately.

The Next Step

Farmers in the Crop Production Groups have applied long established agronomic principles to individual paddocks and in conjunction with other group members measured and interpreted their own results. On this basis they have made individual decisions in relation to time of sowing, the use of minimum tillage and the role of grass-free break crops.

This farming practice is recommended for all who aim to achieve their potential yields.