*Gobal CA-CoP* *CONSERVATION AGRICULTURE COMMUNITY OF PRACTICE*
*for sustainable production intensification and land management*
Dear Subscribers,
Please see herebelow two documents shared by Krishna Naudin of CIRAD
documenting work done on CA in Madagascar.
However, with reference to the first publication, it seems that there are
still some researchers who wrongly state the definition of CA as comprising
of minimum tillage.
*Amir Kassam *
*Moderator*
e-mail: [log in to unmask]
URL: www.fao.org/ag/ca
---------- Forwarded message ----------
From: Krishna NAUDIN <[log in to unmask]>
Date: Mon, Sep 4, 2017 at 1:41 PM
Subject: 2 articles about CA
To: [log in to unmask]
Dear Amir
Please find attached below news about two articles from our (current and
ex) PhD students in Madagascar.
Regards
Krishna
----------------------
*Agro-ecological functions of crop residues under conservation agriculture.
A review*
- Lalaina RanaivosonEmail author <[log in to unmask]>
- Krishna Naudin
- Aude Ripoche
- François Affholder
- Lilia Rabeharisoa
- Marc Corbeels
Agronomy for Sustainable Development August 2017, 37:26
https://link.springer.com/article/10.1007/s13593-017-0432-z
Abstract
Conservation agriculture, which is based on minimum tillage, permanent soil
cover and crop rotations, has widely been promoted as a practice to
maintain or improve soil quality and enhance crop productivity. To a large
extent, the beneficial effects of conservation agriculture are expected to
be provided by permanent soil cover with crop residues. Surface crop
residues play an important role for crop growth through their benefits on
soil-related structural components and processes in the agro-ecosystem,
referred to in this study as agro-ecological functions. Through a
meta-analysis of the literature, we have studied the relative effects of
surface crop residue levels on the performance of a set of agro-ecological
functions compared with a no-till bare soil, i.e., without surface
residues. The selected agro-ecological functions were soil water
evaporation control, soil water infiltration, soil water runoff control,
soil loss control, soil nutrient availability, soil organic carbon (SOC)
stocks and gains, weed control and soil meso- and macrofauna abundance. The
potential effects of crop residue cover were quantified using boundary line
models. Our main findings were (1) 8 t ha−1 of residues were needed to
decrease soil water evaporation by about 30% compared to no-till bare soil.
(2) To achieve the maximum effect on soil water infiltration, water runoff
and soil loss control, residue amounts of at least 2 t ha−1 were required.
(3) The effect of increasing the amounts of surface crop residues on soil
nutrient supply (N, P and K) was relatively low; the boundary line models
were not significant. (4) The average annual SOC gain increased with
increasing amounts of residues, with a mean of 0.38 t C ha−1 year−1 with 4
to 5 t ha−1 of residues. (5) Weed emergence and biomass can be reduced by
50% compared to a no-till bare soil with residue amounts of 1 t ha−1 or
more. (6) There was a weak response in soil meso- and macrofauna abundance
to increasing amounts of surface crop residues. The maximum effect
corresponded to an increase of 45% compared to a no-till bare soil and was
reached from 10 t ha−1 of residues. Our findings suggest that optimal
amounts of surface residues in the practice of conservation agriculture
will largely depend on the type of constraints to crop production which can
be addressed with mulching.
*Can conservation agriculture improve crop water availability in an erratic
tropical climate producing water stress? A simple model applied to upland
rice in Madagascar*
Bruelle, G., Affholder, F., Abrell, T., Ripoche, A., Dusserre, J., Naudin,
K., Tittonell, P., Rabeharisoa, L., Scopel, E.
Agricultural Water Management
http://www.sciencedirect.com/science/article/pii/S0378377417
302500?via%3Dihub
Abstract
Family farms in the tropics mainly rely on rainfed agriculture. Water
availability is limited to rainfall and is one of the main constraints to
crop productivity. Conservation agriculture (CA) is promoted as an
alternative that, among other functions, enhances water infiltration and
limits evaporation from the soil thanks to a mulch of crop residues left on
the soil surface. These functions are assumed to reduce the water
availability constraint by limiting water stress during crop growth. But
the variability of rainfall distribution combined with the wide range of
agroecological conditions and the variety of crop husbandries in the
tropics makes it difficult to evaluate the efficiency of mulching. The aim
of this study was to capture the variability through a simple modeling
approach using the crop growth model PYE-CA, which requires a limited set
of parameters and a virtual experiment (VE). We applied our approach to a
case study of upland rice in the Lake Alaotra region in Madagascar, where
rainfall distribution is highly variable. The VE used a 17-year series of
weather data with a range of soil water conditions, sowing dates, and
growth and yield limitations that cover the variability of agroecological
conditions and management systems in the study area. The VE revealed that
variable successions of wet and dry episodes during the rainy season
resulted in both water stress and an increase in deep drainage. In the
majority of conditions simulated, enhancing water infiltration through CA
mainly increased water loss through drainage. However, better water
infiltration may also reduce the production risks involved in early sowing
or crop intensification, thereby offering new opportunities to farmers. As
an alternative to time consuming and labor intensive experimentation, we
propose a suitable modeling approach to identify the main drivers of
rainfall × crop interactions that could be extrapolated to other regions in
the tropics.
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