Economic and environmental comparison of conventional and conservation agriculture in South African wheat production

Figures & data

Table 1. Impact categories used in the LCA for CA and conventional wheat production in South Africa (Stepwise method).

Category	Units	Description
Carcinogens	kg C2H3Cl-eq	Human toxicity from carcinogens (e.g., pesticides, chemicals)
Non-carcinogens	kg C2H3Cl-eq	Human toxicity from non-carcinogens (e.g., heavy metals)
Respiratory inorganics	kg PM2.5 eq	Primary and secondary particulate emissions
Ionizing radiation	Bq C-14-eq	Damages to human health and ecosystems that are linked to the emissions of radionuclides
Ozone layer depletion	kg CFC-11-eq	Accumulated ozone-depleting compounds emissions
Ecotoxicity, aquatic	kg TEG-eq w	Ecosystem toxicity associated with emissions to water bodies
Ecotoxicity, terrestrial	kg TEG-eq	Ecosystem toxicity associated with emissions to land
Nature occupation	m^2-years agri	Agricultural land occupation – a proxy for effects on biodiversity
Global warming potential	kg CO2-eq	Accumulated greenhouse gas emissions (IPCC 2006 characterisation factors)
Acidification	m^2 UES	Terrestrial acidification driven by acid gases; UES =Unprotected Ecosystem
Eutrophication, aquatic	kg NO3-eq	Freshwater and marine eutrophication driven by nutrient run-offs
Eutrophication, terrestrial	m^2 UES	Excess nutrients on land
Respiratory organics	pers*ppm*hr	Human health effects from volatile organic compounds
Photochemical ozone, vegetation	m2*ppm*hr	Damage to vegetation estimated from ozone emission
Mineral extraction	MJ extra	Mineral extraction energy consumption
Non-renewable energy	MJ primary	Fossil fuel energy consumption

Table 2. Average yield and production costs (R2020) per hectare for no-till and zero-till in Tygerhoek and Langgewens: 2002–2020.

Location/Tillage	N	Wheat yield (ton/ha)		Cost (R/ha)a
Tygerhoek	572	Mean	SD	Mean	SD
• No-till		3.61	1.00	4,512	677.24
• Zero-till		3.37	1.52	4,425	568.59
Langgewens	471
• No-till		3.43	1.02	5,455	1,276.34
• Zero-till		3.30	0.83	5,238	2,094.73
• Conventional^b		3.4	–	5,671	–

^a Summation of all costs associated with one hectare of wheat production given specified test plot inputs averaged across all years of production (see inputs in Appendix).

^b Yield assuming a good year scenario (Knott 2015).

Table 3. Environmental impact costs (in R2020) for various wheat production methods using the Stepwise LCIA method for one kg of wheat production in Western Cape, South Africa.

	Langgewens					Tygerhoek
	No-till	Zero-till	Conventional tillage^a			No-till	Zero-till
			Poor	Average	Good
Total environmental cost (single score)^b	0.887	0.646	2.919	1.796	1.374	0.711	0.599
Human toxicity, carcinogens	0.0129	0.0101	0.0452	0.0278	0.0213	0.0131	0.0095
Human toxicity, non-carcinogens	0.0102	0.0065	0.0275	0.0169	0.0129	0.0085	0.0062
Respiratory inorganics	0.2891	0.2104	0.9198	0.5660	0.4328	0.2396	0.1930
Ionizing radiation	0.0003	0.0002	0.0008	0.0005	0.0004	0.0003	0.0002
Ozone layer depletion	0.0001	0.0000	0.0002	0.0001	0.0001	0.0001	0.0000
Ecotoxicity, aquatic	0.0009	0.0007	0.0026	0.0016	0.0012	0.0010	0.0007
Ecotoxicity, terrestrial	0.0152	0.0098	0.0420	0.0258	0.0198	0.0112	0.0088
Nature occupation	0.0069	0.0049	0.0206	0.0127	0.0097	0.0062	0.0045
Global warming, fossil	0.5240	0.3835	1.7687	1.0884	0.8323	0.4087	0.3567
Acidification	0.0036	0.0026	0.0117	0.0072	0.0055	0.0030	0.0024
Eutrophication, aquatic	0.0010	0.0008	0.0035	0.0022	0.0016	0.0013	0.0012
Eutrophication, terrestrial	0.0128	0.0094	0.0430	0.0264	0.0202	0.0097	0.0085
Respiratory organics	0.0005	0.0004	0.0017	0.0011	0.0008	0.0004	0.0004
Photochemical ozone, vegetation	0.0094	0.0069	0.0312	0.0192	0.0147	0.0076	0.0066
Mineral extraction	0.0003	0.0002	0.0007	0.0004	0.0003	0.0002	0.0001

^a Conventional wheat production based on LCA inputs sourced from Knott (2015). Knott (2015) established three wheat yields scenarios based on seasonal variations: poor, average and good yield with 1.6, 2.6, and 3.4 ton/ha for conventional tillage wheat production in the Western Cape, respectively.

^b Summation of all impact categories. Single score value in R2020.

Table 4. Estimated net profit per hectare (R2020) for CA wheat production in Western Cape, South Africa.

	Average profit^a	5% confidence interval	95% confidence interval
Tygerhoek
• No-till	9,200	−748	19,638
• Zero-till	8,598	2,050	16,936
Langgewens
• No-till	7,590	523	16,271
• Zero-till	7,318	537	14,953
• Conventional tillage^b	6,512

^a Calculated from Equation (2).

^b Profit for a good year scenario (Knott 2015).

Table 5. Average total benefits (R2020 /ha) associated with switching to CA from conventional tillage systems with varying yields per hectare in Langgewens.

	Net profit difference^a		Ecosystem damage cost difference^b		Total benefits^c
	Zero-till	No-till	Zero-till	No-till	Zero-till	No-till
Conventional Good Yield	55	327	2,538	1,629	2,593	1,956
Conventional Average Yield	3,098	3,370	2,538	1,629	5,636	4,999
Conventional Poor Yield	6,902	7,174	2,538	1,629	9,440	8,803

^a Calculated using Table 4 and estimates from Knott (2015). Point estimate of profit for conventional wheat production from Knott (2015) in R2020 are 7,263, 4,220, and 416 per ha for good, average, and poor yield, respectively.

^b Calculated by multiplying Table 3 single scores by wheat yields in Table 2.

^c Obtained from Equation (4).

Table 6. Estimated probability of being more profitable per hectare by switching from conventional tillage with varying yields to CA systems in Langgewens.

	Straight Profit		Environmental and Economic Benefits
	Zero-till	No-till	Zero-till	No-till
Conventional Good Yield	47.93%	46.39%	70.26%	62.03%
Conventional Average Yield	74.67%	73.54%	89.86%	85.57%
Conventional Poor Yield	95.52%	95.53%	99.06%	97.39%

Note: The conventional profits for good, average, and poor yield were estimated in R2020 at 7,263, 4,220, and 416 per ha hectare, respectively (Knott 2015). Percentages were based on 1,000 simulations from Table 5’s profits comparing CA to conventional tillage profitability.

Table 7. Environmental benefits (R2020) of complete adoption of zero and no-till wheat production in the Western Cape from conventional tillage practice.

	Conventional tillage	Zero-till	No-till
LCA single score (per kg)^a	1.37	0.65	0.89
Yield (Mt)^b	3.40	3.30	3.43
Total hectares needed for 2020 wheat crop^c	319,101	328,731	316,504
Environmental cost for entire wheat crop^d	1,490,393,565	701,155,109	962,590,581
Reduction relative to conventional tillage	–	−789,238,456	−527,802,984
Total Reduction in ecosystem damages from CA adoption^e	–	−402,511,613	−269,179,522

^a From Table 3.

^b From Table 2 and Knott (2015).

^c Total output of 2020 dryland wheat crop in Western Cape was 1,084,944 MT (Southern African Grain Laboratory [SAGL] 2021). Thus, hectares needed are estimated by dividing total output by the mean yield of each respective tillage practice.

^d The product of the LCA single score, yield per hectare, and number of hectares needed for total Western Cape crop.

^e Given that estimated CA adoption in WC was 51% in Western Cape (Smith 2021), as such only 51% of potential benefits have been derived from CA wheat production.

Table A1. List of inputs used per hectare in the Stepwise LCIA by location (Langgewens or Tygerhoek) and wheat production system (no-till, zero-till, or conventional till).

			Langgewens		Tygerhoek		Langgewens (Knott 2015)
Group	Description / Product name (Active ingredients)	Unit	No-till	Zero-till	No-till	Zero-till	No-till	Conv.
Fuel (Diesel)
	Pre-harvest/harvest farming operations	litre/ha	27.3	23.9	26.2	26.6	20.5	27.65
Fertilization and amendments
	Nitrogen	kg/ha	75.7	53.6	58.5	49.34	60.0	120.0
	Phosphorus	kg/ha	15.1	9.6	18.7	8.32	14.0	14.0
	Potassium	kg/ha	3.8	3.7	–	0.01	1.0	1.0
	Sulphur	kg/ha	0.3	3.8	11.4	2.00	9.0	9.0
	Calcitic lime	kg/ha	173.1	51.0	243.3	–	–	–
	Dolomitic lime	kg/ha	152.6	79.4	–	–	500.0	500.0
	Gypsum lime	kg/ha	176.5	140.5	8.9	–	–	–
	Manganese sulphate	kg/ha	0.02	–	–	–	–	–
	Potassium sulphate	kg/ha	0.001	–	–	–	–	–
	Bortrac 11%B / LiquiBor 10%B (B-based application)	kg/ha	0.17	0.06	0.01	–	–	–
	Coptrac / Coptrel (Cu-based application)	litre/ha	0.07	–	–	–	–	–
	Foliamag (Mg-based application)	litre/ha	0.001	–	–	–	–	–
	Mantrac (Mn-based fertiliser)	kg/ha	0.04	–	–	–	–	–
	Solubor 20.5%B (B-based application)	kg/ha	0.003	–	–	–	–	–
	Zintrac (Zn-based fertiliser)	kg/ha	0.03	–	–	–	–	–
Pesticides
Weed control
	2.4D Amien (Dimethylamine salt)	litre/ha	0.02	0.10	0.3	0.5	–	–
	Achieve (Tralkoxydim)	litre/ha	0.03	–	0.01	–	–	–
	Ally (Carfentrazone-ethyl/metsulfuron methyl)	g/ha	–	–	0.7	–	–	–
	Aurora (Carfentrazone-ethyl)	Kg/ha	0.001	0.01	0.003	0.01	0.02	0.02
	Axial (Pinoxaden)	litre/ha	0.09	–	0.01	–	–	–
	Boxer (Prosulfocarb)	kg/ha	0.07	–	0.1	0.04	–	–
	Bromoksinil-225 / Buctril-DS (Bromoxynil)	litre/ha	–	–	0.1	0.1	0.5	0.5
	Brush-off / Ally-20DF (Metsulfuron-methyl)	g/ha	0.88	0.77	0.3	4.3	–	–
	Cossack (Iodosulfuron-methyl-sodium/mesosulfuron-methyl/mefenpyr-diethyl)	kg/ha	0.03	–	1.4	–	–	–
	Derby 175 SC (Florasulam/flumetsulam)	litre/ha	0.01	–	–	–	–	–
	Difflan (Diflufenican)	litre/ha	–	–	–	0.003	–	–
	Ecopart (Pyraflufen-ethyl)	litre/ha	–	–	0.01	–	–	–
	Express Super (Chlorsulfuron/metsulfuron-methyl/tribenuron methyl)	g/ha	–	–	4.4	–	–	–
	Garlon (Triclopyr)	litre/ha	–	–	0.1	–	–	–
	Glean / Reaper (Chlorsulfuron)	g/ha	–	–	0.7	3.2	–	–
	Glyran / Glyran-710 (Glyphosate[ammonium])	kg/ha	–	–	0.23	0.2	–	–
	Harmony M (Metsulfuron-methyl/thifensulfuron)	g/ha	–	–	6.3	–	–	–
	Hoelon (Diclofop-methyl)	litre/ha	–	–	0.1	–	–	–
	Hussar (Iodosulfuron-methyl-sodium/mefenpyr-diethyl)	litre/ha	0.004	–	0.04	–	–	–
	Logran (Triasulfuron)	g/ha	1.11	–	1.6	–	0.02	0.02
	MCPA (2-methyl-4-chlorophenoxyacetic acid)	litre/ha	0.03	–	0.4	0.5	–	–
	Pallas (Pyroxsulam)	litre/ha	0.01	–	0.004	–	0.4	0.4
	Paraquat / Skoffel / Gramoxone / Paragone / Preeglone	litre/ha	0.91	0.69	0.9	0.7	1.5	1.5
	Resolve (Bromoxynil/pyrasulfotole/mefenpyr-diethyl)	litre/ha	0.11	0.90	–	–	–	–
	Roundup / Erase / Sting / Glyphosate360 (Glyphosate [isopropylamine])	litre/ha	–	0.90	1.3	2.6	3.0	3.0
	Roundup WSG /Erase granule / Glyphosate WSG (Glyphosate [sodium])	kg/ha	–	–	0.5	–	–	–
	RoundupTurbo (Glyphosate[potassium])	litre/ha	–	–	–	1.4	–	–
	Sakura (Pyroxasulfone)	kg/ha	0.02	0.10	0.002	0.12	–	–
	Topik (Clodinafop-propargyl)	litre/ha	0.02	–	0.006	–	–	–
	Trifluralin / Triflurex / Crew (Trifluralin)	litre/ha	0.79	–	1.1	–	1.5	1.5
Pest control
	Bulldock (Beta-cyfluthrin)	litre/ha	0.01	–	–	–	–	–
	Chlorpyrifos	litre/ha	–	–	0.04	–	–	–
	Cylam (Lambda-cyhalothrin 50 g/litre)	litre/ha	–	–	0.01	–	–	–
	Cyperfos 500EC / Cyperphos (Chlorpyrifos/cypermethrin)	litre/ha	0.05	–	0.04	–	0.8	0.8
	Cypermetrin	litre/ha	–	–	0.01	–	–	–
	Dimethoate / Fetron / Demet / Rogor (Dimethoate)	litre/ha	0.14	–	0.56	1.21	0.5	0.5
	Double star (Acetamiprid)	litre/ha	–	–	–	0.26	–	–
	Folimat (Omethoate)	litre/ha	–	–	0.02	–	–	–
	Lirifos (Chlorpyrifos 480 g/litre)	litre/ha	–	–	0.05	–	–	–
	Metasystox (Oxydemeton-methyl)	litre/ha	–	–	0.18	–	–	–
	Methomex / Methomyl 200 (Methomyl)	kg/ha	0.08	–	0.01	–	–	–
	Mospilan (Acetamiprid)	g/ha	38.74	20.00	28.08	39.69	–	–
	Slakpille (Sluggem [Carbaryl/metaldehyde])	kg/ha	–	–	0.16	–	–	–
Fungal control
	Abacus (Epoxiconazole/pyraclostrobin)	litre/ha	0.07	0.89	–	0.20	–	–
	Acanto (Picoxystrobin)	litre/ha	–	–	0.04	0.12	–	–
	Bumper (Propiconazole)	litre/ha	0.12	–	0.06	–	0.5	0.5
	Capitan (Flusilazole)	litre/ha	–	–	0.03	–	–	–
	Ceriax (Epoxiconasole/fluxapyroxad/pyraclostrobin)	litre/ha	–	–	–	0.01	–	–
	Duet Ultra (Epoxiconazole/thiophanate-methyl)	litre/ha	–	–	–	0.11	–	–
	Duett (Carbendazim/thiophanate-methyl)	litre/ha	0.65	–	0.34	–	0.8	0.8
	Folicur / Tebuconazole / Embrace/ Orius (Tebuconazole)	litre/ha	0.14	–	0.06	–	–	–
	Opus (Epoxiconazole)	litre/ha	0.26	–	0.17	–	–	–
	Prosaro (Prothiconazole/tebuconazole)	litre/ha	–	–	0.06	0.17	–	–
	Prosper Trio (Spiroxamine/tebuconazole/triadimenol)	litre/ha	0.04	0.44	–	0.41	–	–

Note: Conv = Conventional tillage. Active ingredients identified from AVCASA (Association of Veterinary and Crop Associations of South Africa) manuals 2018 (www.croplife.co.za).

Table A2. Average annual wheat prices per ton adjust to 2020 ZAR by location and CA system extracted from Western Cape Department of Agriculture dataset (2021).

Location	CA system	Year	Price
Langgewens	No-till	2002	4232.18
		2003	3106.67
		2004	2451.28
		2005	2690.74
		2006	3213.50
		2007	4199.55
		2008	3527.86
		2009	2915.40
		2010	3865.57
		2011	3605.73
		2012	4652.04
		2013	4603.51
		2014	4511.74
		2015	5366.13
	Zero-till	2016	4372.79
		2017	4654.04
		2018	4667.69
		2019	3814.86
		2020	3761.00
Tygerhoek	No-till	2002	4278.29
		2003	3078.24
		2004	2207.67
		2005	2568.40
		2006	2985.20
		2007	4696.30
		2008	3764.06
		2009	2944.57
		2010	3491.58
		2011	3576.21
		2012	4612.87
		2013	4039.05
		2014	3926.78
		2015	4859.45
	Zero-till	2016	3711.20
		2017	4063.12
		2018	3874.88
		2019	3847.91
		2020	3816.11

Note: Prices adjusted for wheat quality grade (GRAIN SA, 2022).

Table A3. Environmental damage by location and farming practice estimated using Stepwise LCIA for 1 kg of wheat produced in Western Cape, South Africa.

		Langgewens^a						Langgewens		Tygerhoek
		No-till			Conventional			No-till	Zero-till	No-till	Zero-till
		Average	Good	Poor	Average	Good	Poor
Impact category	Unit	Environmental damage
Human toxicity, carcinogens	kg C2H3Cl-eq	0.0025	0.0020	0.0039	0.0039	0.0030	0.0064	0.0018	0.0014	0.0019	0.0013
Human toxicity, non-carcinogens	kg C2H3Cl-eq	0.0016	0.0012	0.0025	0.0023	0.0018	0.0038	0.0014	0.0009	0.0012	0.0009
Respiratory inorganics	kg PM2.5 eq	0.0002	0.0002	0.0003	0.0003	0.0002	0.0005	0.0002	0.0001	0.0001	0.0001
Ionizing radiation	Bq C-14-eq	0.6528	0.5100	1.0201	0.9434	0.7214	1.5330	0.5095	0.3811	0.4856	0.4066
Ozone layer depletion	kg CFC-11-eq	0.0000	0.0000	0.0000	0.0000	0.0000	0.0000	0.0000	0.0000	0.0000	0.0000
Ecotoxicity, aquatic	kg TEG-eq w	6.1215	4.7824	9.5649	8.0193	6.1324	13.0314	4.7651	3.3466	5.0545	3.4098
Ecotoxicity, terrestrial	kg TEG-eq s	0.5292	0.4135	0.8269	0.8723	0.6671	1.4175	0.5144	0.3299	0.3767	0.2959
Nature occupation	m^2-years agri	0.0024	0.0019	0.0038	0.0038	0.0029	0.0062	0.0021	0.0015	0.0019	0.0013
Global warming, non-fossil	kg CO2-eq	0.0002	0.0002	0.0003	0.0003	0.0002	0.0005	0.0001	0.0001	0.0001	0.0001
Global warming, fossil	kg CO2-eq	0.2710	0.2117	0.4234	0.4892	0.3741	0.7950	0.2356	0.1724	0.1837	0.1603
Acidification	m^2 UES	0.0208	0.0162	0.0324	0.0348	0.0266	0.0566	0.0172	0.0126	0.0146	0.0118
Eutrophication, aquatic	kg NO3-eq	0.0006	0.0005	0.0010	0.0008	0.0006	0.0013	0.0004	0.0003	0.0005	0.0004
Eutrophication, terrestrial	m^2 UES	0.0433	0.0338	0.0676	0.0797	0.0610	0.1295	0.0387	0.0283	0.0293	0.0257
Respiratory organics	pers*ppm*hr	0.0001	0.0001	0.0001	0.0002	0.0001	0.0002	0.0001	0.0001	0.0001	0.0001
Photochemical ozone, vegetation	m^2*ppm*hr	1.1258	0.8795	1.7590	1.9294	1.4754	3.1353	0.9423	0.6919	0.7667	0.6585
Non-renewable energy	MJ primary	2.2596	1.7653	3.5306	3.5866	2.7427	5.8283	1.8310	1.4063	1.6434	1.4066
Mineral extraction	MJ extra	0.0021	0.0017	0.0033	0.0038	0.0029	0.0061	0.0025	0.0014	0.0015	0.0013

^a From Knott (2015).

Knott, S.C. 2015. An analysis of the financial implications of different tillage systems within different crop rotations in the Swartland area of the Western Cape, South Africa. MS thesis. Stellenbosch University.

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Smith, H.J. 2021. An assessment of the adoption of conservation agriculture in annual crop-livestock systems in South Africa.

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Data availability statement

Data is available from the authors upon request.