# Diversity of crop residue mulches in Conservation Agriculture and their role in water retention

Akhtar A. Iqbal, Sylvie Recous, P. Thiébeau, Patricia Garnier

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Akhtar A. Iqbal, Sylvie Recous, P. Thiébeau, Patricia Garnier. Diversity of crop residue mulches in Conservation Agriculture and their role in water retention. Conference: XIth ESA Congress, 2010, 2010, 10.13140/RG.2.2.33002.98245. hal-02753872

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# Diversity of crop residue mulches in Conservation Agriculture and their role in water retention

Poster - August 2010

DOI: 10.13140/RG.2.2.33002.98245

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Akthar Iqbal

COMSATS University Islamabad, Abbottabad campus, Pakistan

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Pascal Thiébeau

French National Institute for Agricultural Research

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Sylvie Recous

French National Institute for Agricultural Research

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Patricia Garnier

French National Institute for Agricultural Research

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Some of the authors of this publication are also working on these related projects:

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ecobilan C-N-eau colza View project

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Mesures et Métrologie en Agronomie View project
# Diversity of crop residue mulches in Conservation Agriculture and their role in water retention

Akhtar Iqbal<fnref n="1" />, Sylvie Recous<fnref n="1" />, Pascal Thiebeau<fnref n="1" />, Patricia Garnier²

akhtar.iqbal@reims.inra.fr

Conservation agriculture (CA) is defined as to save the resources for agricultural crop production and it aims to achieve acceptable profits together with high and sustained production levels. Conservation tillage and mulch play a vital role in moisture conservation, water infiltration, maintaining temperature and stabilizing soil structure. In semi-arid regions, mulching has been shown to be effective in reducing the risk of crop failure at field level due to better capture and use of rainfall (Kronen, 1994). It also retards the initial evaporation of water (Bond & Willis, 1969). The capacity of the mulch to capture rain water and to retard the evaporation depends on many factors like type of mulch, biomass and rate of soil cover and physical and chemical properties. According to Findeling et al.(2007) and Coppens et al.(2007), maximum water retention of mulch particles is an important parameter in modeling the decomposition of mulch, controlling the exchanges between soil, mulch and the atmosphere and influencing the activity of soil microorganisms.

In this context, the specific objectives of this study were to identify different types of mulches in the CA situations according to crop species (with pure or mixed crops), their biomass characteristics (amount, thickness) and their water retention properties.

<figure><img src="image_8.png" /><figcaption>**Figure 1:** Schematic diagram representing the moisture retention by mulch</figcaption></figure>

## Materials and Methods

*Survey of agricultural situations:*

The diversity of agricultural situations was established by visiting different farms belonging to France Nouricia network (partner of the Pepites project) in 2009 and by surveying the field experiments of the three other situations (organic farming in Rhône-Alpes area, experimental sites in Madagascar and in Brazil). From this survey we deduced the types of crops involved, the scenarios of crop rotations and therefore the type and characteristics of residue mulches.

*Estimation of mulch biomass and thickness:*

The biomass of crop residues forming mulch was estimated by sampling residues within metallic frame of 0.5 m x 0.5 m area, 10 to 14 times per plot depending on the cutting width of the harvesting

<footnote n="1">¹ INRA, UMR614 Fractionnement des Agroressources et Environnement, 2 esplanade Roland Garros, F-51100, Reims, France., ² INRA, UMR Environnement et Grandes Cultures, EGC Inra Agro-ParisTech, F-78500 Thiverval-Grignon, France.</footnote>
machine. Then the residues were dried at 40°C for 48 hours and dry matter was determined. The thickness of the mulch was determined by using a relief meter adapted to mulches. The relief meter was composed of 55 rods (each spaced 2 cm) and was applied two times per plot, providing an estimation of mulch thickness every 2 cm over 2 transects of 1.10 m length. The thickness of the mulch was estimated as the mean values of 110 measures per plot.

Measurement of maximum water retention:

The water retention properties were first assessed on maize which is a crop present in all rotations of the project, by using stems of 5cm particle size as an experimental model representing field mulch particles. Briefly, the particles were immersed in 1200 ml deionized water for 30 hours and weighed after removal from water (determination of maximal water retention). Residual water (Minimal water retention) was then determined after drying, and calculated as the difference in water content of particles dried at 40°C and 120°C.

Results and Discussion

In the situations of northern France (Nouricia network), there were mainly two situations, mulches of single crops (Maize, wheat, canola etc.) or mulches of mixed crops formed by a main crop + a cover crop (e.g. Wheat + grass/legume mixed). In other situations of the project, the diversity of situations was much greater, e.g association of several crops (e.g. maize + signal grass + Cajan pea + Crotalaria at Madgascar) or in rotation (e.g. Rice + Cajan pea). The biomass of mulch depended on the type of residues, climate and practices adopted for production, varying from 2 to 14 t/ha. In the situation explored (sunflower, canola, wheat etc.), the thickness of mulches varies from 7 to 13 mm.

The maximum absorbed water content of residue was 3 g/g of non decomposed residue. The residual water content was 0.04g/g of residue. If we interpret our observations in the context of field conditions, we can compare the water absorbed by residues and the water potentially added by rainfall. Equivalent “field” conditions for the experimental conditions of this laboratory study correspond to an amount of 750 g of maize mulch / m², which, according to the maximal water retention measured, is expected to absorb 2250 g of water/ m² i.e. 2.3 mm H₂O. This maximal water absorption by the mulch can be compared to a rain of 5 mm, a usual rainfall in northern France.

Conclusion

According to its water storage capacity, large amount of rain can be potentially retained by maize mulch. This amount may depend upon the nature of mulch (physical & chemical properties), the amount of biomass and rate of soil cover and the intensity of rain. Additionally, mulch retention would increase part of the rain that can be retained by soil due to the decrease in runoff (Bennie & Hensley, 2001). So, mulch can play a vital role in conserving moisture which is a very important factor in increasing productivity, especially in semi-arid regions.

References

Bennie A.T.P, Hensley M, 2001. Maximizing precipitation utilization in dryland agriculture in South Africa-a review. Journal of Hydrology, 241, 124-139.

Bond J. J. & Willis, W.O, 1969. Soil water evaporation: surface residue rate and placement effects. Soil Science Society of America Proceedings, 33, 445-448.

Coppens F, Garnier P, Findeling A, Merckx R, Recous S, 2007. Decomposition of mulched versus incorporated crop residues: Modelling with PASTIS clarifies interactions between residue quality and location. Soil Biology and Biochemistry, 39, 2339-2350.

Findeling A, Garnier P, Coppens F, Lafolie, Recous S, 2007. Modelling water, carbon and nitrogen dynamics in soil covered with decomposition mulch. European Journal of Soil Science, 58, 196-206.

Kronen M, 1994. Water harvesting and conservation techniques for smallholder crop production system. Soil and Tillage Research, 32, 71-86.
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PROCEEDINGS OF
Agro2010
the XIth ESA Congress

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August 29th - September 3rd, 2010
Montpellier, France

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