Effects of innovative long-term soil and crop management on topsoil properties of a Mediterranean soil based on detailed water retention curves
Authors: Aldaz-Lusarreta Alaitz , Giménez Rafael , Campo-Bescós Miguel A. , Arregui Luis M. , Virto Iñigo 
Published: October 2022

Abstract. The effectiveness of conservation agriculture (CA) and
other soil management strategies implying a reduction of tillage has been
shown to be site-dependent (crop, clime and soil), and thus any new soil and
crop management should be rigorously evaluated before its implementation.
Moreover, farmers are normally reluctant to abandon conventional practices
if this means putting their production at risk. This study evaluates an
innovative soil and crop management (including no-tillage, cover crops and
organic amendments) as an alternative to conventional management for rainfed
cereal cropping in a calcareous soil in a semi-arid Mediterranean climatic
zone of Navarra (Spain), based on the analysis of soil water retention
curves (SWRCs) and soil structure. The study was carried out in a small
agricultural area in the municipality of Garínoain (Navarre, Spain) devoted
to rainfed cereal cropping. No other agricultural area in the whole region
of Navarre exists where soil and crop management as proposed herein is
practiced. Climate is temperate Mediterranean, and the dominant soil is
Fluventic Haploxerept. Within the study area there is a subarea devoted to the proposed soil and
crop management (OPM treatment), while there is another subarea where the
soil and crop management is conventional in the zone (CM treatment). OPM
includes no-tillage (18 years continuous) after conventional tillage, crop
rotation, use of cover crops and occasional application of organic
amendments. CM involves continuous conventional tillage (chisel plow),
mineral fertilization, no cover crops and a lower diversity of crops in the
rotation. Undisturbed soil samples from the topsoil and disturbed samples
from the tilled layer were collected for both systems. The undisturbed
samples were used to obtain the detailed SWRCs in the low suction range using a
HYPROP©device. From the SWRCs, different approaches found in the
literature to evaluate soil physical quality were calculated. The pore-size
distribution was also estimated from the SWRCs. Disturbed samples were used
in the laboratory to assess soil structure by means of an aggregate-size
fractionation and to perform complementary analysis from which other
indicators related to soil functioning and agricultural sustainability were
obtained. The approaches evaluated did not show clear differences between
treatments. However, the differences in soil quality between the two forms
of management were better observed in the pore size distributions and by
the analysis of the size distribution and stability of soil aggregates.
There was an overabundance of macropores under CM, while the amount of
mesopores (available water) and micropores were similar in both treatments.
Likewise, more stable macroaggregates were observed in OPM than in CM, as
well as more organic C storage, greater microbial activity, and biomass. The
proposed management system is providing good results regarding soil physical
quality and contributing also to the enhancement of biodiversity, as well as to the
improvement in water-use efficiency. Finally, our findings suggest that the
adoption of the proposed practice would not result in a loss in yields
compared to conventional management.