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Trial: The effect of controlled traffic and direction of traffic on run-off, erosion, crop yield and gross margins Central Queensland Sustainable Farming Systems Project (CQSFSP) GRDC Research Project: DAQ 382 Results: 1998-2000

Keywords: Central Queensland, Capella, Moonggoo, Central Queensland Sustainable Farming Systems Project, Controlled Traffic (CT), Round-the-Contour (RTC), nitrogen, water use, yield, water use efficiency Summary of results: Controlled traffic (CT) out-yielded Round-the-contour (RTC) in all treatments for all crops except for the zero N treatment in 1999 sorghum. These results are from five crops over three years, three rates of nitrogen application and two different paddocks. The water use efficiency was usually higher in the CT treatments as compared to the RTC treatments. These differences cannot be statistically proven due to lack of replication.

More detail: • Location Summary • Photos: • Results Notes: • Interpreting Replicated Trials

Background:

The Capella district is situated north of Emerald towards the north end of the cropping belt on the eastern coast of Australia. This district was selected as an area to form a group as part of the Central Queensland Sustainable Farming Systems Project (CQSFSP) due to the importance of cropping to the area.

The development site is on 'Moonggoo', the property of Barry, David and Alan Storey. It was ideal for the project work as the fertility was run down and it was conducive to the directional tillage treatments.

Two reasonably uniform adjacent paddocks were identified on Moonggoo (north and south paddock). The last crop in the north paddock produced wheat of 9% protein showing the paddock was not yielding to its full capacity. The adjacent paddock (south) was in sunflower stubble. It was decided to install the Controlled Traffic (CT) and Round The Contour (RTC) systems in both paddocks to determine the effects of the different stubble cover levels.

Soil compaction has been observed in the study area and represents the most noticeable form of degradation. Compaction can have the effect of reducing rooting depth and PAWC through structural degradation. Nutrient levels (nitrogen, sulfur, and zinc) are shown to be low and represent the decline in soil fertility. There are no adverse chemical conditions such as high sodicity or salinity recorded which would limit crop growth.

Why do the trial:

There has been a big push to promote controlled traffic (CT) with all the advantages of controlled wheel tracks (e.g. ease of spraying, no compaction in cropping area, quicker to get on land after rain). Unfortunately, the CT system contradicts previous recommended practice by advocating that producers farm their land up and down the hill (over the contours) rather than round the hill (parallel with the contour). The existing practise of round the contour (RTC) farming was thought to be the best way of retaining rainfall on the paddock and the new CT farming was proposing the exact opposite.

Although the farmers in the group saw the potential benefits of CT farming, they were concerned that the planting furrows down the hill would facilitate the run-off of water and leave the paddock drier after rainfall than if planted in the conventional direction.

How was it done:

Figure 1: diagram of North and South paddocks at Moonggoo

1998

South paddock

• Planted to sunflowers early 1998.
• Two treatments of controlled traffic and round the contour were overlaid by 3 nitrogen treatments, zero N, budget N (40 kg N/ha) and high N (60 kg N/ha).

North paddock

• Planted to wheat 1998.
• The CT and RTC treatments were overlaid by three nitrogen rates, zero N, budget N (25 kg N/ha) and high N (60 kg N/ha).

1999

The trial was changed a little to incorporate the Storey's whole farm conversion to controlled traffic. The CT areas remained the same but the RTC areas became RTC in controlled traffic lanes.

South paddock

• Planted to sorghum late December 1998.
• The CT and RTC treatments were overlaid by 3 nitrogen treatments replicated once, zero N, budget N (30 kg N/ha) and high N (60 kg N/ha).

North paddock

• Planted to sunflower early 1999.
• The CT and RTC treatments were overlaid by three nitrogen treatments replicated once, zero N, budget N (35 kg N/ha) and high N (60 kg /ha).

2000

South paddock

• Planted to sorghum early 2000.
• The CT and RTC treatments were overlaid with three nitrogen treatments, zero N, budget N (40 kg N /ha) and high N (60 kg /ha).
• This trial was hit by rain before harvest, which severely decreased the yield and quality.

• The south paddock had a full soil profile in August 2000, and the group decided to plant a spring crop - probably sorghum.

North paddock

• Planted to wheat in April.
• The CT and RTC treatments were overlaid by three nitrogen treatments replicated once, zero N, budget N (40 kg N/ha) and high N (60 kg N/ha). (Results not ready at time of writing)

A range of indicators were developed by the group to measure the success of treatments. These include:

• Soil water and nitrogen at prior to planting and immediately after harvest events
• Yield, oil and protein contents
• Plant populations established

What happened:

1998 Sunflower crop (North paddock)

The CT area had more nitrate at planting, more plant available water at planting and a higher plant population established than the RTC treatment. Yields and oil percentage in the CT were higher in all of the nitrogen treatments as a result of these three factors. After harvest, the nitrate in the CT was lower as the higher population with more plant available water would have used more nitrogen in producing crop growth and yield. There was more nitrogen left in the RTC despite there being less available at planting.

In-crop rain was 151 mm in total with approximately 100 mm being effective. Both the CT and RTC were zero tilled with two sprays being applied to the wheat stubble during the fallow.

1998 Wheat crop (South paddock)

CT strips had similar available nitrate as the RTC strips at planting. The available water was lower in the RTC. The plant populations were slightly higher in the RTC although the CT strips put out more heads.

The yields were slightly higher and the proteins were the same and higher, in the CT as compared to the RTC, which would be expected with reasonable nitrogen levels, more PAW at planting and more heads after tillering. The nitrate levels at harvest were highest in the RTC which was related to the lower yield and protein produced. With rain late in the crop, the PAW at harvest is higher than that at planting in both cases by approximately 60 mm.

1999 sorghum crop (South paddock)

The decision was made to opportunity crop the south paddock more aggressively and following good rain, the paddock was planted to sorghum on 5 December 1998. An earlier planting was attempted but the ground was too wet.

When comparing CT to RTC, the N at planting was very low in the zero strips (8 kg N/ha in CT and 9 kg N/ha in RTC). The budgeted and 60 kg N/ha had residual N 27 and 33 kg N/ha in CT and with 32 and 26 kg N/ha in the RTC. With the applied N at planting this brought the totals up to reasonable levels.

The main difference was the CT treatment had approximately 170 mm of plant available water at planting compared with approximately 130 mm in the RTC. This could be due to extra traffic in the RTC but the only wheels on the RTC were for the in-fallow spraying.

Yield was higher in all CT treatments as compared to the RTC treatments. This difference in water could explain the yields being slightly higher in the CT strips although there was still moisture in the soil at harvest. The population established was also higher in the CT areas (32 000 as compared to 28 000 plants/ha) which would have contributed to a better yield in the CT.

The RTC strips had lower yields but the test weights were slightly higher. Moisture varied between 12.4 - 13.0% (desirable < 13.5%) across the trials and screenings between 2.7 - 4.8% (desirable < 10%) with cracked grain accounting for the majority of the screenings.

The yield results suggest that controlled traffic farming will produce higher yields independent of crop nutrition.

1999 sunflower crop (North paddock)

This was the first year the nitrogen strips were replicated. The soil these replicates were placed on had been put down to budget N in 1998.

Populations were again low with the CT better at 18 000 plants/ha as opposed to 12 000 plants/ha, which makes the results extremely difficult to interpret as this is confounding the data. The nitrate at planting was good in the CT and RTC strips. All strips had low nitrate at harvest except the CT 60 kg N/ha treatment.

The starting water in the RTC was higher on average with approximately 130 mm as opposed to approximately 90 mm on the CT. There was very little water present at harvest in any of the treatments. The yields in the CT treatments were all consistently higher than compared to the RTC treatments. However responses to nutrition trends were the same for both CT and RTC, with 0 kg N/ha lowest and 60 kg N/ha highest yielding. The oil percentage was also consistently higher in CT than RTC. This is pointing towards the idea that CT will produce higher yielding crops with better water use efficiencies. As growers' main concern is to utilise the water in their soils for the best return, these results are extremely interesting and are generating a lot of thought amongst the group, especially those who are not using a controlled traffic system.

2000 sorghum crop (South paddock)

The Storeys accidentally fertilised the second zero N strip with the budget rate of fertiliser (40 kg N/ha) which meant that the zero strip was not replicated but the budget strip was replicated twice. The Storeys also had a problem with spraying in the crop. They were recommended a post-plant spray application for weed control. However, time constraints and the sorghum emerging early meant the RTC treatment had been spayed before they realised that the sorghum was emerging. The spray was then changed for the CT treatment. This is probably one of the reasons for the plant population results being much lower and variable in the RCT treatments.

When comparing CT with RTC, the first most obvious difference is the plant populations. Plant populations were extremely variable between and within the treatments. Both the CT and RTC N treatments followed the trend of very little nitrate available at planting in the 0 kg N/ha strips and steadily increasing as the rates of N increased. This was expected, except the amount of N available at planting in the 60 kg N/ha strip in CT was approximately double that available in the same strip in RTC. The nitrate in the 60 kg N/ha strips appears to be building up quicker in CT than in RTC as seen by the residual nitrate in these strips in 1999 (see Tables 6 & 7).

We are not exactly sure why this is occurring as the CT is consistently producing greater yields and should be accessing more nitrogen. The amounts of nitrogen after harvest are approximately the same for all treatments. The plant available water at planting was highest for the 0 kg N/kg strip, but approximately the same at harvest between rates of N. The water use efficiencies are higher in CT for the budget and high rate of N as compared to these treatments in the RTC treatment.

The yields were highly variable this year with no clear trend, due to the effects of the variable plant populations. The results are confounded due to plant population rather than any other treatment effects. The highest yielding treatment was in the CT 40 kg N/ha treatment, followed closely by the CT 60 kg N/ha and then RTC 40 kg N/ha. The protein is consistently higher in RTC as would be expected due to the lower yielding crop, except for the 0 kg N/ha treatments. The results are still indicating that the CT 40 kg N/ha is the "best" treatment.

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Location Summary:

	Capella
Soil Type:	Mainly self-mulching, black cracking clay (Vertosol)
Paddock History:	North	South
2000:	Wheat	Sorghum
1999:	Sunflower	Sorghum
1998:	Wheat	Sunflower
Rainfall (mm):
Av. annual:	587 mm
Actual annual 1998:	823mm
Actual annual 1999:	313 mm
Actual annual 2000 (Jan to June):	752 mm

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Results:

1. Table 1: Overall yield and oil results for sunflower crops

		Controlled Traffic		Round the Contour
Paddock	Fertiliser	Yield (t/ha)	Oil (%)	Yield (t/ha)	Oil (%)
South (1998)	0 kg N/ha	0.554	40.2	0.46	39.5
	40 kg N/ha	0.636	39.5	0.515	39.1
	60 kg N/ha	0.664	39.0	0.511	37.8
North (1999)	0 kg N/ha	1.00	41.4	0.74	40.7
	35 kg N/ha	1.13	41.9	0.92	40.4
	60 kg N/ha	1.21	41.1	0.91	39.8

2. Table 2: Overall yield and protein results for sorghum crops

		Controlled Traffic		Round the Contour
Paddock	Fertiliser	Yield (t/ha)	Protein (%)	Yield (t/ha)	Protein (%)
South (1999)	0 kg N/ha	1.48	6.9	1.07	7.0
	30 kg N/ha	2.36	7.4	2.05	8.4
	60 kg N/ha	2.69	8.8	1.92	8.5
South (2000)	0 kg N/ha	1.45	7.2	1.97	8.4
	40 kg N/ha	2.58	8.7	2.23	9.6
	60 kg N/ha	2.45	9.8	1.55	9.9

3. Table 3: Overall yield and protein results for wheat crops

		Controlled Traffic		Round the Contour
Paddock	Fertiliser	Yield (t/ha)	Protein (%)	Yield (t/ha)	Protein (%)
North (1998)	0 kg N/ha	1.79	12.5	1.69	12.3
	25 kg N/ha	1.85	12.9	1.79	12.9
	60 kg N/ha	1.83	13.4	1.79	12.9

4. Table 4: Summary of soil nitrate, soil water, plant and harvest data for 1998 sunflower crop at Moonggoo (planted 24/02/98, harvested 14/07/98)

	Controlled Traffic			Round-the-contour
	0 N	40 kg N/ha	60 kg N/ha	0 N	40 kg N/ha	60 kg N/ha
Soil nitrate
Planting profile N (kg/ha)	61	70	60	24	63	48
Harvest profile N (kg/ha)	11	19	38	16	63	21
Soil water
Planting profile PAWC (mm)	70	80	69	46	58	59
Harvest profile PAWC (mm)	46	39	39	25	26	27
In-crop rain (mm)	100	100	100	100	100	100
WUE (mm/kg/ha)	4.5	4.5	5.1	3.8	3.9	3.9
Population and Yield
Plant population plants/ha)	22 500	24 600	21 100	17 600	20 400	20 800
Yield (t/ha)	0.554	0.636	0.664	0.46	0.515	0.511
Oil (%)	40.2	39.5	39	39.5	39.1	37.8

5. Table 5: Summary of soil nitrate, soil water, plant and harvest data for 1998 wheat crop at Moonggoo (planted 01/05/98, harvested 24/09/98)

	Controlled Traffic			Round-the-contour
	0 N	25 kg N/ha	60 kg N/ha	0 N	25 kg N/ha	60 kg N/ha
Soil nitrate
Planting profile N (kg/ha)	74	132	99	87	124	109
Harvest profile N (kg/ha)	14	17	50	35	31	31
Soil water
Planting profile PAWC (mm)	98	92	74	65	65	66
Harvest profile PAWC (mm)	131	139	126	96	123	123
In-crop rain (mm)	299	299	299	299	299	299
WUE (mm/kg/ha)	7.0	7.6	7.8	6.6	7.8	7.7
Population and Yield
Plant population plants/ha)	443 000	470 500	487 000	520 500	501 000	490 000
Yield (t/ha)	1.79	1.85	1.83	1.69	1.79	1.79
Protein (%)	12.5	12.9	13.4	12.3	12.9	12.9

6. Table 6: Summary of soil nitrate, soil water, plant and harvest data for 1999 sorghum crop at Moonggoo (planted 05/12/98, harvested 31/03/99)

	Controlled Traffic			Round-the-contour
	0 N	30 kg N/ha	60 kg N/ha	0 N	30 kg N/ha	60 kg N/ha
Soil nitrate
Planting profile N (kg/ha)	21	31	34	9	62	86
Harvest profile N (kg/ha)	4	6	50	4	3	15
Soil water
Planting profile PAWC (mm)	161	169	170	129	131	135
Harvest profile PAWC (mm)	83	64	59	81	90	80
In-crop rain (mm)	304	304	304	304	304	304
WUE (mm/kg/ha)	3.9	5.8	6.5	3.0	5.9	5.4
Population and Yield
Plant population plants/ha)	32 000	32 000	32 000	28 000	28 000	28 000
Yield (t/ha)	1.48	2.36	2.69	1.07	2.05	1.92
Protein (%)	6.9	7.4	8.8	7.0	8.4	8.5

7. Table 7: Controlled traffic - Summary of soil nitrate, soil water, plant and harvest data for 1999 sunflower crop at Moonggoo (planted 19/01/99, harvested 18/06/99)

	Controlled Traffic			Round-the-contour
	0 N	35 kg N/ha	60 kg N/ha	0 N	35 kg N/ha	60 kg N/ha
Soil nitrate
Planting profile N (kg/ha)	37	40	59	35	60	49
Harvest profile N (kg/ha)	5	14	30	10	13	15
Soil water
Planting profile PAWC (mm)	98	94	79	105	132	131
Harvest profile PAWC (mm)	10	2	4	6	7	15
In-crop rain (mm)	203	203	203	203	203	203
WUE (mm/kg/ha)	3.5	3.9	4.4	2.5	2.8	2.8
Population and Yield
Plant population plants/ha)	18 000	18 000	18 000	12 000	12 000	12 000
Yield (t/ha)	1.00	1.13	1.21	0.74	0.92	0.91
Oil (%)	41.4	41.9	41.1	40.7	40.4	39.8

8. Table 8: Controlled traffic - Summary of soil nitrate, soil water, plant and harvest data for 2000 sorghum crop at Moonggoo (planted 21/01/00, harvested 26 & 27/05/00)

	Controlled Traffic			Round-the-contour
	0 N	40 kg N/ha	60 kg N/ha	0 N	40 kg N/ha	60 kg N/ha
Soil nitrate
Planting profile N (kg/ha)	1.6	32.5	105.8	1.0	23.4	50.1
Harvest profile N (kg/ha)	5.7	5.9	9.3	4.7	8.1	12.7
Soil water
Planting profile PAWC (mm)	221	157	145	269	149	198
Harvest profile PAWC (mm)	135	125	115	115	114	117
In-crop rain (mm)	590	590	590	590	590	590
WUE (mm/kg/ha)	2.1	4.0	4.0	2.3	3.3	2.3
Population and Yield
Plant population plants/ha)	41 719	42 617	39 421	27 083	21 918	14 128
Yield (t/ha)	1.451	2.577	2.452	1.973	2.234	1.553
Protein (%)	7.2	8.7	9.8	8.4	9.6	9.9

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For more detail contact:

Jayne Kuskie, QDPI, Ph: 07 4983 7436, E-mail: kuskiej@dpi.qld.gov.au

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