Insects attack vegetable crop, leading to an overuse of pesticides. Organic amendments are recommended to increase soil fertility. The impact of two insecticides, on soil macrofauna under rainfed cultivation of tomato ( Lycopersicon esculentum L.) with or without organic amendments was evaluated. The insecticides were Lambda Super (lambda-cyhalothrin) and Dursban (chlorpyrifos ethyl) and organic amendments were compost, pig manure and cattle manure. An experimental device in split-plot with three replicate was installed. Pesticides were applied periodically each week during the experiment. The results have showed that with organic amendments, Lambda super increased the earthworm population compared to the control. Indeed, we found 42 individuals/m 2 with compost; 1 individuals/m 2 with pig manure and 27 individuals/m 2 with cattle manure but the control was 0 individuals/m 2 in the presence of Lambda super without organic amendment. Similarly, Dursban increased the population of earthworms in the presence of organic amendment with 11, 37 and 91 individuals/m 2 respectively for compost, pig manure and cattle manure. Lambda super with compost has led to a total elimination of termites. In the presence of Dursban, a decrease in the number of termites was observed when adding cattle manure (11 individuals/ m 2) compared to the control containing only Dursban (21 individuals/m 2). Better distribution of macrofauna was obtained with treatment with Dursban and compost (E = 0.99 for earthworms and E = 0.96 for termites). All organic amendments used in our study stimulated earthworm population, but more in the presence of Lambda super or Dursban.
Tomato (Solanumly copersicum L.) is grown all over the world, and is an important part of the diet. Tomato is the main vegetable in Burkina Faso [
In Burkina Faso, organic amendments are recommended by the government for soil fertility management. Some studies from [
However, there is a lack of information on the contribution of organic amendments to reduce the effects of pesticides on soil non-target macrofauna. The objective of this study is to evaluate the effects of pesticides used in vegetable production on soil macrofauna in the presence of organic amendment. This is in order to find some recommendable organic amendments for farmers to reduce the impact of pesticides on soil fertility. We issued the following assumptions: 1) organic amendments, in the presence of functional groups and a wide variety of microorganisms are able to retain and stimulate the degradation of pesticides in soil and reduce their impact on soil macrofauna; 2) the ability to reduce the effect of pesticides on soil macrofauna depends on the organic amendments used.
The study was conducted in the rainy season at Kamboinsé (12˚28'N, 1˚32'W, 296 m above sea level) in 2013 in northern Burkina Faso located in the Soudanian climatic zone with a mean temperature of 27˚C. The site was chosen to get the same type of soil and to work in intense pest invasion area.
The rainy season is from June to September with an average rainfall of 1000 mm per year. The study has been conducted for 130 days. The soils of Kamboinsé area are mostly ferruginous leached, based on the deep sandy material, hydromorphic soils with little humus pseudogley inherited in association with lithosols on ironstone [
A split plot design with three replications was laid out. The main treatment was the use of insecticides. Lambda super 2.5 EC (25 g/l lambda-cyhalothrin) applied at the recommended rate (600 ml/ha); and Dursban 4E (480 g/l of Chlorpyrifosethyl) applied at the recommended rate (1.25 l/ha). The pesticides were applied three times during the tomato growth cycle (130 days). The first applied was 21 days after the experiment set up and 10 days after each application. The plots were 3 m × 10 m and 1 m apart.
The sub treatment was the use of organic amendment that includes a control without organic amendment, green waste compost (from a mixture of green waste (74%); cattle manure (24%) and Burkina phosphate), pig manure and cattle manure. The organic amendment was applied at the recommended rate of 20t/ha. The size of sub plots was 12 × 9 m. The blocks were separated by an alley of 1, 5 m.
Tomato (Lycopersicon esculentum) was used as plant material for our experiment. The variety used was F1 Mongal, which is rainfed, matures in 130 days and has average yields ranging between 40 and 50 tons per hectare. It is tolerant to tomato virus (TYLCV), Fusarium sp., Stemphylium sp., nematodes and Pseudomonas sp. [
Monolith sampling of soil macrofauna was done according to the standard TSBF
Clay | Silt | Sand | Ct | Nt | C/N | Kt | Pt | pHw | |
---|---|---|---|---|---|---|---|---|---|
g·kg−1 | mg·kg−1 | ||||||||
Soil | 14.42 | 24.76 | 60.82 | 007.30 | 00.45 | 16.22 | 1088.5 | 936.1 | 06.18 |
Cattle manure | - | - | - | 411.20 | 24.80 | 16.54 | 10250.0 | 8210.0 | 07.96 |
Compost | - | - | - | 210.00 | 13.20 | 16.41 | 6220.0 | 19787.9 | 08.32 |
method [
Composite soil samples from five spots at 0 - 20 cm were taken from each plot after crop harvest using an auger. Samples were sieved through 2 mm mesh for chemical and physical parameters determinations.
Analysis of variance (ANOVA) was performed using a General Linear Model (GLM) implemented in Genstat Discovery Edition 4 statistical software for Windows. Differences were significant at p < 0.05 according to Tukey’s tests. Species diversity was expressed using Shannon index
A total of 267 earthworms belonging to Acanthodrilidae family were collected. It was Millsonia inermis and Dichogaster affinis. Dichogaster affinis, a shallow species that feeds the soil from the horizon 0 - 10 cm dominated in the experiment (82% of the total density of earthworms). Millsonia inermis (18% of the total density of earthworms) live at 30 - 40 cm depth but come to the soil surface to feeds on the organic fraction.
The results showed that without organic amendment, the presence of lambda super (lambda-cyhalothrin) led to a total disappearance of earthworms. Under the same conditions, the earthworm population remained stable in the presence of Dursban (chlorpyrifos ethyl) compare to the control (5 individuals/m2). How- ever, the effect of both pesticides was not significant.
In this study, 939 individuals of termites were collected represented by Odontotermes sp. belong to the mushroom family and Trinervitermes sp, from reapers family. Dursban and Lamba super increased the density of termites to 21 individuals/m2 and 16 individuals/m2 respectively compared to the control without pesticides (0 individuals/m2) (
Treatments | Species | Number/m2 | Total density (individual/m2) | IS | E |
---|---|---|---|---|---|
M0P0 | Dichogaster affinis | 05 | 05a ± 9.23 | 0.000 | 0.000 |
M0P1 | - | 00 | 00a ± 0,00 | 0.000 | 0.000 |
M0P2 | Dichogaster affinis | 05 | 05a ± 9.23 | 0.000 | 0.000 |
M1P0 | Dichogaster affinis | 21 | 21a ± 9.23 | 0.000 | 0.000 |
M1P1 | Dichogaster affinis Millsonia inermis | 37 05 | 42a ± 18.47 | 0.364 | 0.520 |
M1P2 | Dichogaster affinis Millsonia inermis | 05 06 | 11a ± 9.23 | 0.689 | 0.990 |
M2P0 | Dichogaster affinis | 05 | 05 a ± 9.23 | 0.000 | 0.000 |
M2P1 | Dichogaster affinis | 11 | 11a ± 9.23 | 0.000 | 0.000 |
M2P2 | Dichogaster affinis | 37 | 37a ± 18.47 | 0.000 | 0.000 |
M3P0 | Dichogaster affinis | 11 | 11a ± 9.23 | 0.000 | 0.000 |
M3P1 | Dichogaster affinis | 27 | 27a ± 9.23 | 0.000 | 0.000 |
M3P2 | Dichogaster affinis Millsonia inermis | 80 11 | 91b ± 15.30 | 0.368 | 0.530 |
M0: Control without organic amendment; M1: compost; M2: Pig manure; M3: Cattle manure; P0: Control without pesticide P1: Lambda super P2: Dursban In a same column, values affected with the same letter are not significantly different at p < 5%.
Treatments | Species | Number/m2 | Density of termites (individual/m2) | IS | E |
---|---|---|---|---|---|
M0P0 | - | 000 | 000a | 0.000 | 0.000 |
M0P1 | Odontotermes sp. | 016 | 016a | 0.000 | 0.000 |
M0P2 | Trinervitermes sp. | 021 | 021a | 0.000 | 0.000 |
M1P0 | Trinervitermes sp. | 139 | 139a | 0.000 | 0.000 |
M1P1 | - | 000 | 000a | 0.000 | 0.000 |
M1P2 | Trinervitermes sp. Odontotermes sp. | 101 155 | 256a | 0.670 | 0.960 |
M2P0 | - | 000 | 000a | 0.000 | 0.000 |
M2P1 | Trinervitermes sp. | 085 | 085 | 0.000 | 0.000 |
M2P2 | Odontotermes sp. Trinervitermes sp. | 213 085 | 298a | 0.357 | 0.515 |
M3P0 | Odontotermes sp. Trinervitermes sp. | 075 028 | 103a | 0.354 | 0.510 |
M3P1 | Odontotermes sp. | 011 | 011a | 0.000 | 0.000 |
M3P2 | Trinervitermes sp. | 011 | 011a | 0.000 | 0.000 |
M0: Control without organic amendment M1: compost M2: Pig manure M3: Cattle manure P0: Control without pesticide P1: lambda super P2: Dursban In a same column, values affected with the same letter are not significantly different at p < 5%.
ganic amendment + Dursban (21 individuals/m2). The best Evenness was ob- tained with Dursban + compost treatment (E = 0.96). The highest termites diversity was observed with pig manure and Dursban treatment (M2P2, IS = 0.357) and compost with Dursban (M1P2, IS = 0.670) and cattle manure without pesticide (M3P0, IS = 0.354). Relative to the average value of the Shannon index (0.128), only M2P2, M1P2 M3P0 had a higher diversity than average (
The inventory has raised 501 individuals belonging to groups other than termites and earthworms. These macrofauna groups were represented in 7 orders that are Ants, Coleoptera, Hemiptera, Collembola, Myriapoda, Arachnida and Diptera (
Compared to their respective control without organic amendment (26.66 for Lambda super and 5.33 for Dursban), Lambda super (32 - 75 individuals/m2) and Dursban (22 - 52 individuals/m2) have increased the density of the groups in the presence of organic amendments. With both pesticides, the trend of the evolution of these groups of macrofauna was: M2 > M3 > M1.
Treatments | Groups | Individuals /m2 | Total number |
---|---|---|---|
M0P0 | Ants | 11 | 16ab |
Coleoptera | 05 | ||
M1P0 | Coleoptera Hemiptera Ants Collembola | 32 05 05 05 | 47ab |
M2P0 | Coleoptera Myriapoda Ants | 38 05 32 | 75b |
M3P0 | Ants Coleoptera Myriapoda | 32 11 05 | 48ab |
M0P1 | Coleoptera Arachnida Ants | 11 05 11 | 27ab |
M1P1 | Coleoptera Arachnida | 27 05 | 32ab |
M2P1 | Coleoptera Ants Arachnida Collembola | 27 32 11 05 | 75b |
M3P1 | Coleoptera | 43 27 | 70b |
Ants | |||
M0P2 | Coleoptera | 05 | 05a |
M1P2 | Ants Diptera | 17 05 | 22ab |
M2P2 | Coleoptera | 42 | 52ab |
Arachnida | 05 | ||
Ants | 05 | ||
M3P2 | Arachnida Ants Coleoptera Collembola | 05 11 11 05 | 32ab |
M0: Control without organic amendment; M1: compost; M2: Pig manure; M3: Cattle manure P0: Control without pesticide; P1: lambda super; P2: Dursban In a same column, values affected with the same letter are not significantly different at p < 5%.
Considering the effects of pesticides on earthworms, results showed that Dursban (chlorpyrifos ethyl) and Lambda super (lambda-cyhalotrin) had no significant effect on the density of earthworms. The capacity of macrofauna to degrade pesticides and decrease their effect has been observed by many authors. Bhattacharya and Sahu [
Termites were represented by Odontotermes sp., a mushroom grower cultivating their fungi in soils galleries, and Trinervitermes sp., a reaper feeding on litter. Pesticides have stimulated the density of termites in the soil. In fact, the mode of action and toxicity of pesticides are not only based on the nature of the product and the dose used, but also the group of targeted individuals and the stage of growth. Parvathi et al. [
The chlorpyrifos ethyl and compost treatment had the best index of diversity and evenness of earthworms and termites. This shows that the compost is most favorable to the balanced and diversified development of earthworms and termites. Our results confirm those of Ouédraogo [
Our results showed a decrease of the number of Ants, Coleoptera, Hemiptera, Collembola, Myriapoda, Arachnida and Diptera in the presence of chlorpyrifos ethyl. These results are similar to those of Endlwerber et al. [
With both pesticides, the trend of the evolution of other groups of macrofauna is: M2 > M3 > M1. This evolutionary trend is the same as the C/N ratio of organic amendments. Organic amendments with a C/N ratio are those indicated for reducing the effects of pesticides on macrofauna groups other than termites and earthworms. This will allow a good availability of nutrients for plants and also better performance. Ouédraogo et al. [
The objective of this study was to evaluate the effects of pesticides on soil macrofauna in the presence of organic amendments. The results showed that the effect of lambda-cyhalothrin and chlorpyrifos ethyl on soil macrofauna depends on the nature of the pesticide and macrofauna group. Both pesticides have boosted the density of termites, but only chlorpyrifos ethyl had led to a decline in the density of macrofauna groups other than termites and earthworms. From our results, we can conclude that organic amendments helped reduce the effects of lambda-cyhalothrin on soil termite and other group of macrofauna. The same effect was observed with chlorpyrifos ethyl, except termites in the presence of cattle manure.
The use of organic amendments should always be recommended; however, appropriated pesticide should be chosen to avoid their impacts on soil organisms. For ecological agriculture, the use of lambda-cyhalothrin should be encouraged because its effects are quickly neutralized by organic amendment. Our results mean also that organic amendment and earthworms could be used for soil depollution.
This work was financed by International Foundation for Science (IFS) through grant number C/5002-1 awarded to the first author.
Nare, R.W.A., Savadogo, P.W., Traore, M., Gountan, A., Nacro, H.B. and Sedogo, M.P. (2017) Soil Macrofauna Behaviour in the Presence of Pesticides and Organic Amendments. Journal of Geoscience and Environment Protection, 5, 202-212. https://doi.org/10.4236/gep.2017.53014