A comparison of herbicide mixtures as labor saving technology in Nwoya district

Sneyers Koen - Lanek Polycarp – Robert Ogweng

ZOA Uganda - October 2015

INTRODUCTION

Intensification of the smallholder agricultural sector in Uganda strongly depends on the use of agro chemicals and fertilizer inputs. ZOA Uganda made a strategic choice to further explore the potential of herbicide in its agricultural programming for Acholi sub region. Under its project Farmer led soil innovations to sustain food security ZOA identified pilot farmers who already had positive experiences with the integration of herbicides in their farming system. Through participatory on farm discussions between users, integration of these inputs is being finetuned to achieve higher efficiency rates. In order to further understand the benefits and limitations of herbicides, ZOA set up a practical experiments to study its effectiveness at a controlled site in Anaka, Nwoya district.

METHODOLOGY.

The ZOA Farmer Resource Centre in Anaka is a controlled environment where field trials are conducted and farmer communities exposed to improved production practices. The research site is characterized by sandy clay loam and fairly high organic matter content (5-6%) with deficient P values (10-30ppm)1. The site is located along the Gulu-Olwiyo highway in the Amuru-Gulu Groudnut, Rice, Sorghum and Livestock zone (LHZ 172).

During the 2nd season of 2015 5 plots of 3m x 20m were set out at the site on fallow land which was fallow the season before. Weeds were slashed 2 weeks prior to herbicide application. Each plot was treated with a different mixture dissolved in 1l volume of water. Solutions were mixed on the spot and applied by use of a Jacktoe 16l manual spraypump with flat fan nozzle. Calibration of the walking speed ensured full application of the mixture of 1l over the 60m2 area. The application occurred during morning hours and no rain occurred later in the day.

Similarly 8 pilot farmers applied a standard mixture of glyphosate at their farm trial plots scattered over Nwoya district. Technical guidance was provided through practical training

1 IFDC/ISSD Soil maps 2014 2 FEWSNET, Livelihood zoning and mapping exercise Uganda, 2010

prior to the season and is in line with the technical booklet `Safe and correct use of herbicides` as developed by ZOA Uganda.

Mixtures were based on 3 products and dissolved in water originating from a surface water source. Weedall and Willosate (active ingredient N-(phosphonomethyl)glycine or glyphosate 360 g/l), 2-4-D (active ingredient 2,4-Dichlorophenoxyacetic acid 720 g/l) and Diesel fuel. Weedall and Willosate are both common non selective herbicides. The first one was purchased from a local retailer in Gulu, the second one from the supplier EASeed in Kampala directly.

Overview of the different mixtures applied at the research site

Per acre Per spray pump (16l)

Treatment

Glyphosate

(ml) 2-4 D

(ml) Diesel

(ml)

Glyphosate

(ml) 2-4 D

(ml) Diesel

(ml)

1

1,000 - - 240 - -

2

1,000

270 - 240

64 -

3

1,000

540 - 240

128 -

4

1,000 -

540 240 -

128

5

1,000 -

1,400 240 -

320

Effect of the mixture on the currently present range of weed species was analysed by visual observation at 1 week, 2 weeks and 4 weeks after application. Effectiveness was rated at the ordinal level as (0=none, 1=fair and 2=good). The following species were monitored (functional of presence) at the trial plots:

Popular name Scientific name

Spear grass Imperata cylindrica Wandering jew Commelina benghalensis Couch grass Digitaria abyssinica Foxtail Cenchrus ciliaris Wild sunflower Helianthus spp. Wild sorghum Sorghum spp Goat weed Ageratuem coyzides Wild finger milet Eleusine africana Nutt grass Cyperus rotundus Guinea grass Panicum maximum Thatching grass Hyparrhenia rufa Congo signal Rat tail Disocactus flagelliformis Milk weed Cat tail Sporobolus pyramidalis

Overall effectiveness was calculated as the average score of all weed species present with a maximum score of 100% in case all present species were affected as `good` (all ratings 2/2).

A Benefit Cost ratio was calculated by comparing the expected benefits from saved labor for weeding and land opening. Benefits from saved labor on land opening were based on a conservative cost of 10 mandays equal to 80,000 UGX which is saved when 2nd tillage is replace by herbicide use. Benefits from saved labor on weeding (idem) was based on the observation that farmers are able to skip a second weeding operation as soon as they see it feasible. As such the opportunity cost of 160,000 UGX was corrected with the effectiveness score of the herbicide mixtures. Total costs were compiled by summing chemical input costs with a fixed fee which is linked to transaction costs (transport to trading centre) and rent of spraying equipment.

RESULTS

The figures below show the observed impact of the mixtures on those weed species which were present. Weeds which were present on less than 3 of the trial plots or weeds which were not present on the first plot which acted as control (Weedall1000) were excluded from the graphs.

At 2 weeks after herbicide application it is observed that the addition of 2,4D to the standard mixture of glyphosate has a positive effect on Spear grass and Nutt grass. The addition of Diesel appears to have a positive effect on Wild sorghum, Nutt grass and Congo signal. However the effect is not consistent as increased Diesel concentration did not or even negatively influence the effect. The glyphosate brand Willosate (applied on farm plots) scored better than its competing brand Weedall (at the research site) for Spear grass and Napier grass.

Figure 1: Effectiveness of the herbicide mixtures on present weed species 2 weeks after application

At 4 weeks after herbicide application considerable re-growth of weeds was observed. Effectiveness rating was less straightforward in absence of an objective decision framework. In general it was observed that the addition of 2,4D had a positive effect for Nutt grass, Guinea grass and Milk Weed.

Fair

Good

Spear grass Wandering jew

Wild sorghum

Nutt grass Guinea grass Congo signal

Weedall1000

Weedall1000+2,4D270

Weedall1000+2,4D540

Weedall1000+Diesel560

Weedall1000+Diesel1400

Figure 2: Effectiveness of the herbicide mixtures on present weed species 4 weeks after application

The calculated values of average effectiveness indicate a time trend of observable effect over the 3 observation moments. For most treatments the observable effect increases until week 2 and is clearly reduced 4 weeks after application.

Time of observation

Weedall1000 Weedall1000+ 2,4D270

Weedall1000+ 2,4D540

Weedall1000+ Diesel560

Weedall1000+ Diesel1400

Willowsate1440 Willowsate1000 (farmer plots)

1WAP 10% 50% 33% 50% 67% 2WAP 43% 50% 50% 75% 64% 50% 91%

4WAP 21% 43% 20% 20% 0%

The cost benefit ratio of observable effects on the weed species shows that for most of the herbicide mixtures the expected benefits from saved labor stand about a factor 2 in relation to the cost of the agro chemical and fixed costs related to the technology. Only for the Willowsate brand in a sole concentration of 1000ml per acre an B/C ratio of 3.8 is achieved.

Variable cost Fixed cost

Total cost (UGX/acre)

Average effectiveness

Estimated benefits

from saved labor

(UGX/acre) B/C ratio

Glyphosate 2-4 D Diesel Transport &

rent

Weedall1000 18,225 - -

20,000 38,225 43%

68,571 1.8

Weedall1000+2,4D270 18,225

6,750 -

20,000 43,625 50%

80,000 1.8

Weedall1000+2,4D540 18,225

13,500 -

20,000 49,025 50%

80,000 1.6

Weedall1000+Diesel560 18,225 -

1,890

20,000 40,115 75%

120,000 3.0 Weedall1000+Diesel1400 18,225 -

4,725

20,000 42,950 64%

102,857 2.4

Willowsate1440 26,244 - -

20,000 46,244 50%

80,000 1.7

Willowsate1000 18,225 - -

20,000 38,225 91%

145,556 3.8

Fair

Good

Spear grass Wandering jew

Wild sorghum

Nutt grass Guinea grass Congo signal Milk weed

Weedall1000

Weedall1000+2,4D270

Weedall1000+2,4D540

Weedall1000+Diesel560

Weedall1000+Diesel1400

DISCUSSION

Based on the limited observations from the study it appears that there is a visually clear difference in performance between the 2 glyphosate based products. For most weed species the Willosate product performs better than the Weedall brand. As most mixtures were based on the lower performing Weedall it is not surprising that mixtures with additives also performed below expectation. The results confirm the general perception that quality of agro input available in rural areas is of mediocre quality and not able to contribute to the profitability of small scale farming. The author wishes to remark that in a previous trial with products purchased 3 months earlier from the same supplier, Weedall did perform up to standard.

Out of the 3 monitoring moments (1,2 and 4 weeks) it is observed that 4 weeks after application, herbicide effects were less visible. For the majority of the present weeds, benefits appeared limited up to 2 weeks after application. Soon after this period, weed germination over took the achieved suppression. Farmer discussions indicate that for some crop combinations this might be sufficient to reduce weeding frequency from twice to only once per season.

Benefits cost ratios of technologies are a critical factor influencing adoption by smallholder farmers. With a ratio of 3.8 the Willosate product might have more chance to be adopted than its lower performing competitor at 1.8, even when 2,4D herbicide is added to it. The addition of Diesel as cheaper additive appears to have a positive impact on the C/B ratios, however only at low concentration of ½ l per acre.

Follow up research is recommended to further explore the benefits of the Diesel and 2,4D additives on a standard mixture of the better performing Willosate product. Secondly it is recommended that observations can be replicated at multiple plots in which the full range of weed species is present.

ANNEX : PICTURES OF TRIAL PLOTS 1 WEEK AFTER APPLICATION

Plot 1 : Weedall1000 Plot 2: Weedall1000+2,4D270

Plot 3: Weedall1000+2,4D540 Plot 4: Weedall1000+Diesel560

Plot 5: Weedall1000+Diesel1400 Farmers trial plot Willosate1000