7 research outputs found
Effects of innovative long-term soil and crop management on topsoil properties of a mediterranean soil based on detailed water retention curves
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.This study was partially supported by the Ministerio de Economía y Competitividad (Government of Spain) via research project CGL2015-64284-C2-1-R and PID2020-112908RB-I00 funded by 568 MCIN/AEI/10.13039/501100011033/FEDER “Una manera de hacer Europa”
Biological and synthetic approaches to inhibiting nitrification in non-tilled Mediterranean soils
Background: The increasing demand for food production has led to a tenfold increase in nitrogen (N) fertilizer use since the Green Revolution. Nowadays, agricultural soils have been turned into high-nitrifying environments that increase N pollution. To decrease N losses, synthetic nitrification inhibitors (SNIs) such as 3,4-dimethylpyrazole phosphate (DMPP) have been developed. However, SNIs are not widely adopted by farmers due to their biologically limited stability and soil mobility. On the other hand, allelopathic substances from root exudates from crops such as sorghum are known for their activity as biological nitrification inhibitors (BNIs). These substances are released directly into the rhizosphere. Nevertheless, BNI exudation could be modified or even suppressed if crop development is affected. In this work, we compare the performance of biological (sorghum crop) and synthetic (DMPP) nitrification inhibitors in field conditions. Results: Sorghum crop BNIs and DMPP prevented an increase in the abundance of ammonia-oxidizing bacteria (AOB) without affecting the total bacterial abundance. Both nitrification inhibitors maintained similar soil NH4+ content, but at 30 days post-fertilization (DPF), the sorghum BNIs resulted in higher soil NO3− content than DMPP. Even so, these inhibitors managed to reduce 64% and 96%, respectively, of the NO3−-N/NH4+-N ratio compared to the control treatment. Similar to soil mineral N, there were no differences in leaf δ15N values between the two nitrification inhibitors, yet at 30 DPF, δ15N values from sorghum BNI were more positive than those of DMPP. N2O emissions from DMPP-treated soil were low throughout the experiment. Nevertheless, while sorghum BNIs also maintained low N2O emissions, they were associated with a substantial N2O emission peak at 3 DPF that lasted until 7 DPF. Conclusions: Our results indicate that while sorghum root exudates can reduce nitrification in field soil, even at the same efficiency as DMPP for a certain amount of time, they are not able to prevent the N pollution derived from N fertilization as DMPP does during the entire experiment.This project was funded by the Spanish Government (RTI2018-094623-B-C22 MCIU/AEI/FEDER, UE) and by the Basque Government (IT-932-16). Adrián Bozal-Leorri holds a Grant from the Basque Government (PRE-2020-2-0142). Mario Corrochano-Monsalve holds a Grant from the Ministry of Economy and Business of the Spanish Government (BES-2016-076725)
Evaluation of soil moisture estimation techniques based on Sentinel-1 observations over wheat fields
Soil moisture (SM) is a key variable in agriculture and its monitoring is essential. SM determines the amount of
water available to plants, having a direct impact on the development of crops, on the forecasting of crop yields
and on the surveillance of food security. Microwave remote sensing offers a great potential for estimating SM
because it is sensitive to the dielectric characteristics of observed surface that depend on surface soil moisture.
The objective of this study is the evaluation of three change detection methodologies for SM estimation over
wheat at the agricultural field scale based on Sentinel-1 time series: Short Term Change Detection (STCD), TU
Wien Change Detection (TUWCD) and Multitemporal Bayesian Change Detection (MTBCD). Different methodological alternatives were proposed for the implementation of these techniques at the agricultural field scale. Soil
moisture measurements from eight experimental wheat fields were used for validating the methodologies. All
available Sentinel-1 acquisitions were processed and the eventual benefit of correcting for vegetation effects in
backscatter time series was evaluated. The results were rather variable, with some experimental fields achieving
successful performance metrics (ubRMSE ~ 0.05 m3
/m3
) and some others rather poor ones (ubRMSE > 0.12 m3
/
m3
). Evaluating median performance metrics, it was observed that both TUWCD and MTBCD methods obtained
better results when run with vegetation corrected backscatter time series (ubRMSE ~0.07 m3
/m3
) whereas STCD
produced similar results with and without vegetation correction (ubRMSE ~0.08 m3
/m3
). The soil moisture
content had an influence on the accuracy of the different methodologies, with higher errors observed for drier
conditions and rain-fed fields, in comparison to wetter conditions and irrigated fields. Taking into account the
spatial scale of this case study, results were considered promising for the future application of these techniques in
irrigation management.This work was supported by the Spanish Ministry of Science and
Innovation and the European Regional Development Fund (MICINN/
FEDER-UE) through projects [CGL2016–75217-R and
PID2019–107386RB-I00 / AEI / 10.13039/501100011033] and
doctoral grant [BES-2017–080560]. Open access funding provided by the Public University of Navarre