The economics of changing from draper to stripper fronts for increased standing crop residue and improved harvest efficiency

Take home messages

• The most cost-effective means of increasing standing residue and improving harvest efficiency is increasing harvest height with existing machinery.
• Stripper fronts are an economic inclusion to harvest machinery where they replace draper fronts.
• Improved harvest efficiency drives adequate cost reductions to generate good returns on investment in stripper fronts.
• The addition of any benefits achieved from additional income during a wet harvest by reducing the extent of quality downgrading adds further weight to an investment case.
• The projected returns in this analysis are sensitive to business scale. Reductions in scale lead to reductions in returns on investment.
• The assumptions are based on limited stripper front experience thus ground-truthing with more data will be required to draw conclusions specific to circumstance.
• The inclusion of a systems’ specific benefits and reductions in the cost of wet weather at harvest will further improve the investment case for change.

Introduction

This paper is written from an economic rather than an agronomic perspective. The intent is to deliver a case study at a pre-determined business scale to demonstrate the process for conducting investment analysis on header fronts. An economic analysis of the costs and benefits of the inclusion of stripper fronts to disc seeding systems follows. This paper is aimed to complement the analysis of the costs and benefits of disc versus tine seeding equipment which is provided in the paper within this booklet of Swan et al. (2018) titled ‘Flexible stubble management – how to reap returns to the bottom line’.

Introduction to crop residue management

One of the intentional benefits of moving from a tine to a disc seeding system is the benefit of retained crop residue resulting in improved soil moisture retention and improved soil structural characteristics. Plant residues provide physical benefits by protecting the soil surface as well as several biological and soil structural benefits resulting in greater water holding capacity of the soil.

The minimal disturbance of soil in disc seeding systems is proposed to add further benefit by resulting in less soil disturbance. This reduces the chance of soil moisture losses at sowing and results in a lower volume of soil being disturbed thereby reducing depletion of soil structure.

Thus, plant residue management and retention is an important component of a system intent on conserving moisture for subsequent crop growth. The management of plant residues is an important component of the system adopted.

The height that cereal crops are harvested can impact on subsequent seeding practices. Conventional harvest height (30-40cm) can result in a significant proportion of the standing crop moving through the header and being redistributed over the paddock. This redistribution can lead to problems at sowing in disc seeding systems due to the redistributed straw being bent (hair pinning) and pushed into the furrow. This prevents soil to seed contact and reduces even crop emergence.

To overcome this issue some managers have adopted alternative harvest management tactics. One of these tactics is to increase harvest height while another is to move from the use of a conventional header front to the use of a stripper header front.

An explanation outlining how stripper fronts work relative to conventional harvest fronts and highlighting some of the advantages and disadvantages follows. This information is extracted from a paper of Broster, Rayner, Ruttledge and Walsh, 2018.

Stripper fronts use rows of fingers on a spinning rotor to pluck grain heads and pods from mature crop plants. Compared to cutting and collecting the grain-bearing plant sections like conventional header fronts, stripper fronts leave more stubble standing.

By reducing the quantity of material being processed by the harvester, stripper fronts increase the speed and efficiency of harvesting. Anecdotal evidence suggests that stripper fronts are particularly effective in harvesting lodged and fallen crops, as the fingers can lift and remove the heads without the need for collecting large amounts of crop material.

The use of stripper fronts does have some disadvantages. Tall standing stubble carries increased fire risk and requires sowing equipment which can clear the stubble. Harvester settings need to be changed due to the decreased volume being processed, which requires some expertise and experience. A faster harvest rate can have logistical implications - for example; more grain trucks may be required to keep up with the harvester.

Economic comparison of stripper front with draper front

An analysis of the marginal costs and benefits of a harvest system with a stripper front relative to a harvest system with a draper front has been conducted. Trial data from the flexible stubble management project (Swan et al 2018) has been used for some analysis assumptions. Only the harvester and front costs and benefits have been considered in this analysis.

The comparison of the stripper front harvesting at a height of approximately 60cm (stripper high) has been made with a draper front harvesting at conventional height of approximately 40cm (draper low) and with a draper front harvesting at approximately 60cm (draper high) to maintain as much plant residue standing as is practical with a draper front.

An identified constraint with harvesting high using a draper front is that it is improbable that the whole crop will be harvested at a height of 60cm. The reason for this is that a proportion of the crop usually presents harvest feeding difficulties. This has been dealt with in this analysis by assuming that 80% of the total cereal area can be harvested high while the remaining 20% must be harvested at conventional heights and speeds.

One of the key advantages of raising harvest height is the ability to increase the speed of harvest. This improves harvest efficiency by increasing the number of tonnes per hour harvested. This occurs because the reduced residue requires less threshing thus more crop can be harvested at the higher speed.

This advantage expresses itself in cost savings by:

1. Reducing depreciation. Fewer hours harvesting for the same harvested area results in additional ownership tenure with little marginal loss of machinery value.
2. Reducing repairs and maintenance. The reduction in the amount of crop residue moving through the threshing mechanisms of the header results in reduced wear and tear on some header components thereby reducing some repairs and maintenance costs.
3. Reducing fuel costs. Fuel costs are reduced per unit of production and per unit of area due to the decreased horsepower requirements for threshing and due to the increased crop tonnage harvested per hour.
4. Reducing labour costs. Typically, labour is charged on a rate per unit of time. Any increase in efficiency resulting in fewer hours for the same job therefore results in a labour cost saving. This saving typically applies to casual labour which is charged on an hourly rate. Savings in permanent farm labour are not realised unless that portion of saved surplus labour becomes unpaid or is employed off-farm.

Analysis assumptions are provided in Tables 1, 2 and 3. Limited experience with stripper fronts in broadacre dryland crops forms the basis of some of these assumptions. Further experience will result in better quantification and greater confidence around the relative operational differences between header-front use.

Table 1. Draper versus stripper front analysis assumptions.

Table 2. Comparative harvest equipment capital and depreciation costs.

Table 3. Variation in header performance at different harvest heights and fronts.

Figure 1. Large time and cost efficiencies are achieved by increasing harvest height regardless of front choice.

Figure 2. The marginal benefit of moving from a draper to a stripper front is 15 percent in time saved and 12 percent in cost savings.

The use of a draper front at high harvest heights reduces header hours by 10% and header costs by 8% when compared to the use of a draper front at low (conventional) harvest heights. Given there is no capital cost to this change and significant benefit this should be the first step in improving standing plant residue levels.

The use of a stripper front at high harvest heights reduces header hours by 23% and header costs by 21% when compared to the use of a draper front at low (conventional) harvest heights. The economic comparison should not be based on the change from the draper front at conventional height to stripper front rather the change from the draper front at increased height as this option should be progressed first.

The bottom-line

Given that there are large efficiencies to be achieved by moving from a draper front at conventional height to 60cm, and that there is little to no associated capital cost, this should be the first step in increasing standing residue retention.

Based on the assumptions in this analysis the marginal investment in a stripper front, assuming that it replaces a draper front, is $5,000. The annual benefit has been calculated by assessing the difference in costs between using a stripper front and using a draper front high. The marginal value of the increased operating efficiency over a 3,000ha canola wheat rotation is $5.54/ha equating to $16,600 assuming the labour component is not a sunk cost. This generates a return on marginal investment of over 300% and suggests that the operating efficiencies alone are adequate to present a very good business case for investment.

Where the draper front is retained and a stripper front acquired in addition, then the marginal investment increases from $5,000 to $123,000 with the same stream of annual benefits. This reduces the return on investment to 6% which is just above the cost of debt funding.

This suggests that there is no business case for retaining a high value draper front if a stripper front has been purchased. The exception is where the marginal harvest efficiency results in quantifiable benefits during a wet harvest or where the stripper front brings quantifiable and unique systems’ benefits. Additional investment of a magnitude of $80,000 with no additional operating costs results in the rate of return falling to 15%. This suggests that there is scope for the purchase of a lower cost draper front or additional out-loading capacity provided 15% is still an acceptable rate of return.

Wet weather benefits

Increasing height and improving harvest efficiency may also lead to reductions in the cost of weather damage when it occurs. The value of these marginal benefits has not been included in this analysis.

For harvest efficiency to generate value by reducing the quantity of downgraded quality in wet harvests, management can’t stop at the header front. The improved harvest efficiency only generates value in wet weather if the outloading machinery is matched to the increased header capacity. In other words, there is no benefit in the header doing less hours if, from a weather damage perspective, it is consistently stopping and waiting to be unloaded.

In some cases, this will mean that additional investment must also be made in chaser bins, mother bins and trucks. The extent of the required investment will depend on:

• The capacity of the existing machinery.
• The marginal increase in capacity from the change in harvest height.
• The components of the outloading machinery that are owned by the operator.

While it is impossible to predict future events, it is possible to quantify the cost of weather damage by using historical records. Table 4 shows a process for estimating the economic value of weather damaged grain at harvest. The tool considers the annualised marginal cost of the downgrading in value which is dependent on:

• The extent of the price disparity between good and weather-damaged quality,
• the percentage of the crop affected, and;
• the probability or the occurrence of the event.

In the projections shown in Table 4, with 20% probability of a wet harvest, the annualised cost over a 3,000ha crop with assumed yields shown is $18,630 per year.

When considering the value of improved harvest efficiency to reducing quality damage in wet weather it needs to be noted that only a proportion of the cost of harvest weather damage may be offset.

Table 4. The cost of weather damage is dependent on the extent of the price disparity between good and poor quality, the percentage of the crop affected and the probability or the occurrence of the event.

Systems’ benefits of harvest height

A systems-related benefit which is difficult to allocate specifically to the stripper front, is the contribution, over time, of additional standing residue to increased surface soil moisture. This, in theory, could generate more timely sowing opportunities with less emergence problems than systems retaining less standing residue.

No attempt to quantify this benefit has been made in this analysis. If more-timely sowing was achieved over 5% of the crop area and a yield benefit of 5% was achieved as a result then it would deliver $7,031 in additional crop value annually.

Other costs

One study found that grain losses where stripper fronts were used were far higher than those where draper fronts were used for harvest. User experience suggests that improving understanding of how the losses were occurring and investing time in better machinery setup prior to starting can minimise losses regardless of front. This is a management issue thus the cost of grain losses has been assumed to be no different regardless of the header front used.

Conclusion

The most cost-effective means of increasing standing residue and improving harvest efficiency is increasing harvest height with existing machinery. Stripper fronts can generate solid economic returns on investment where they replace draper fronts and where scale is adequate. They must however, be set up efficiently to achieve these benefits. The outcomes of this analysis are specific to this case study however, the process can be followed to establish investment returns where assumptions from this case study vary.

Acknowledgements

The conclusions delivered from the analyses are based on discussions and assumptions drawn from the following sources:

• Trial data generated in the flexible stubble management project (Swan et al. 2018).
• Experiences of farm business managers with a range in farming systems, scale and farm machinery.
• The observations of agronomists working with farm business managers.

Agronomist; Greg Condon, Grassroots Agronomy and farm business managers; Daniel Fox, John Stevenson, Warwick Holding have been instrumental in providing on-farm machinery data and improving the author’s understanding of some of the issues. Their contributions are gratefully acknowledged.

Contact details

John Francis
john@holmessackett.com.au