No abstract

Summary Recent advances suggest that organic substances of different origins might have different aggregate stability dynamics. We investigated the extent to which contrasting soil types affect the dynamics of aggregation after the addition of crop residues (R) and of biochar at two doses (BC20, 20 Mg ha−1; BC40, 40 Mg ha−1) in a 2‐year experiment. To evaluate disaggregation, we measured a set of physical–chemical and structure‐related properties of clay and sandy loam aggregates sieved to 1–2 mm, including wet aggregate stability after different pretreatments combined with laser diffraction analysis. The electrochemical properties of the colloidal suspension were also analysed to identify changes in soil chemistry affected by organic inputs. Different amounts of added biochar and soil types produced contrasting effects on wet aggregate stability. In sandy loam, the increased soil surface area from added biochar (at either dose) offset the initial small soil organic carbon (SOC) content and subsequently promoted SOC‐controlled aggregation. Conversely in clay soil, the larger biochar dose (BC40) strengthened the repulsive forces between particles with the same charge and monovalent cations, which led to chemical perturbation and some aggregate breakdown not found with BC20. Pore structure also changed in clay aggregates. A shift towards more micropores (30–5 μm, + 29% more than in the control) and ultramicropores (5–0.1 μm, + 22% more than in the control), which contributed to aggregate stabilization, resulted when biochar was added, but not for residue. Our results suggest that biochar promotes aggregate stability, which, in turn, improves the physical fertility of soil, especially if it has a coarse texture and small organic carbon content. Further study is needed of the physical–chemical interactions between added biochar and surface‐charged clay‐rich soils. Highlights Aggregate dynamics are poorly understood because of complex interactions between organic inputs and soil type. A multidisciplinary approach was used to study aggregation dynamics. Large biochar input changed soil chemical properties that weakened stability in clay aggregates. Aggregate stability depended on biochar dose and soil type.

No abstract

The surface energy balance algorithm for land (SEBAL) has been successfully applied to estimate evapotranspiration (ET) and yield at different spatial scales. However, ET and yield patterns have never been investigated under highly heterogeneous conditions. We applied SEBAL in a salt-affected and water-stressed maize field located at the margin of the Venice Lagoon, Italy, using Landsat images. SEBAL results were compared with estimates of evapotranspiration by the Food and Agriculture Organization (FAO) method (ET c ) and three-dimensional soil-plant simulations. The biomass production routine in SEBAL was then tested using spatially distributed crop yield measurements and the outcomes of a soil-plant numerical model. The results show good agreement between SEBAL evapotranspiration and ET c . Instantaneous ET simulated by SEBAL is also consistent with the soil-plant model results (R 2 = 0.7047 for 2011 and R 2 = 0.6689 for 2012). Conversely, yield predictions (6.4 t/ha in 2011 and 3.47 t/ha in 2012) are in good agreement with observations (8.64 t/ha and 3.86 t/ha, respectively) only in 2012 and the comparison with soil-plant simulations (8.69 t/ha and 5.49 t/ha) is poor. In general, SEBAL underestimates land productivity in contrast to the soil-plant model that overestimates yield in dry years. SEBAL provides accurate predictions under stress conditions due to the fact that it does not require knowledge of the soil/root characteristics.crop-specific relations between ET and yield [6,7], it provides a measure of both water demand and land productivity. Yield is thus the ultimate indicator to describe crop response to water resource management [8] and the quantification of field scale ET is fundamental for managers to maximize land productivity while minimizing water losses [9][10][11]. Crop yield is also a key element for rural development and national food security. For these reasons, forecasting crop yield a few months before harvest can be of paramount importance for timely initiation of the food trade, securing national demand, and organizing food transport within countries [6,7,12].The yield of many agricultural crops is generally predicted from the amount of water used by the crop, i.e., ET [6,7]. Traditionally, ET from fields has been estimated according to the Food and Agriculture Organization (FAO) method [13], i.e., by multiplying a weather-based reference ET 0 by a crop coefficient (K c ) determined according to crop type and growth stage. However, the suitability of the idealized K c coefficient to describe the actual vegetative and growing conditions, especially in water limited areas, was questioned by many authors [14]. In addition, it is difficult to predict the correct growth stage dates for large populations of crops and fields [15].A viable alternative for mapping evaporation at field and regional scales is the use of satellite images that can provide an excellent tool to detect the spatial and temporal structure of ET [16]. Remote sensing (RS) is a reliable and cost-effective method to forecas...

Increasing soil organic carbon (SOC) stocks in agricultural soils is currently of special interest because it can help mitigate global warming through atmospheric carbon (C) sequestration. Recommended management practices, such as conservation agriculture (CA) and conventional tillage with cover crops (CC), could have significant implications for C sequestration potential. A field experiment was carried out in northeast Italy to compare the implementation of CA and CC with conventional agriculture (CV). The experiment began in 2010 on three farms to evaluate SOC stock variation over a 6-year period. Two extensive soil sampling operations were conducted in 2011 and 2017 in 240 locations, for a total of 1,440 analysed soil samples, considering the SOC stratification within a 0-50-cm profile. The results suggested that CA changed the SOC distribution rather than the total amount of SOC. Compared to CV, after the introduction of CA, a general increase in SOC (0.25 Mg C ha −1 y −1) was observed in the 0-30-cm layer, whereas no stock variation was observed in the 0-50-cm layer. In contrast, compared to CV, the use of CC decreased the SOC stocks by 0.74 Mg C ha −1 y −1 in the 0-50-cm layer. Over a 6-year period, no benefit in SOC sequestration was observed with CA and CC. However, we hypothesize that these findings could still be affected by transitory dynamics, highlighting the low soil reactivity to soil-improving agricultural systems. A longer study period would be required to better understand the potential benefits of CA and CC on SOC sequestration. Highlights

Conservation agriculture (CA) is an agronomic system, including no-tillage, cover crops and residue retention on the soil surface, which represents more sustainable management compared to conventional ploughing systems (CV). Conservation agriculture is widespread in some parts of the world (i.e. South America and the USA), whereas it is still developing in others (i.e. Europe). One of the main reasons for the slow European uptake of CA is low yield because of the worsening of soil physical quality, in particular increased compaction and reduced hydraulic permeability. The effects of CA on soil physical dynamics are poorly documented, particularly during the transition phase between CV and CA and for fine-textured soils. Therefore, in this study, the effects of CA on soil volumetric water content, bulk

No abstract

No abstract