Francesco Morari

Simultaneous Monitoring of Soil Water Content and Salinity with a Low-Cost Capacitance-Resistance Probe

Capacitance and resistivity sensors can be used to continuously monitor soil volumetric water content (θ) and pore-water electrical conductivity (ECp) with non-destructive methods. However, dielectric readings of capacitance sensors operating at low frequencies are normally biased by high soil electrical conductivity. A procedure to calibrate capacitance-resistance probes in saline conditions was implemented in contrasting soils. A low-cost capacitance-resistance probe (ECH2O-5TE, 70 MHz, Decagon Devices, Pullman, WA, USA) was used in five soils at four water contents (i.e., from dry conditions to saturation) and four salinity levels of the wetting solution (0, 5, 10, and 15 dS·m−1). θ was accurately predicted as a function of the dielectric constant, apparent electrical conductivity (ECa), texture and organic carbon content, even in high salinity conditions. Four models to estimate pore-water electrical conductivity were tested and a set of empirical predicting functions were identified to estimate the model parameters based on easily available soil properties (e.g., texture, soil organic matter). The four models were reformulated to estimate ECp as a function of ECa, dielectric readings, and soil characteristics, improving their performances with respect to the original model formulation. Low-cost capacitance-resistance probes, if properly calibrated, can be effectively used to monitor water and solute dynamics in saline soils.

Effects of four cultivation systems for maize on nitrogen leaching 1. Field experiment

Abstract An experiment was conducted for 3 years on the Venetian Plain (northeast Italy) to evaluate the environmental impact of four cropping systems at different input levels. The four systems were: (A) higher inputs with pesticides, chemical fertilizers and liquid manure; (B) higher inputs with pesticides and chemical fertilizers; (C) lower inputs with low doses of fertilizers, post-emergence herbicides and use of cover crops; (D) organic, with low inputs without artificial fertilizers or pesticides. To assess the environmental impact samples of groundwater, soil and crop were taken from one field in each system, cultivated with maize but subjected to various management strategies. The results showed large differences in the nitrate nitrogen (NO 3 -N) concentration in the shallow groundwater, ranging from a mean value of 7.89mgl −1 in system A to 2.21 mg l −1 in system C. Less variability was observed for total Kjeldhal nitrogen (TKN): a maximum of 5.69 mg l −1 for system D and a minimum of 2.74mg l −1 for system B. Total annual nitrogen losses (TKN + N-NO 3 ) were 48, 19, 16 and 15 kg ha −1 year −1 in the four cultivation systems, respectively.

Degradation of soil fertility can cancel pollination benefits in sunflower

Pollination and soil fertility are important ecosystem services to agriculture but their relative roles and potential interactions are poorly understood. We explored the combined effects of pollination and soil fertility in sunflower using soils from a trial characterized by different long-term input management in order to recreate plausible levels of soil fertility. Pollinator exclusion was used as a proxy for a highly eroded pollination service. Pollination benefits to yield depended on soil fertility, i.e., insect pollination enhanced seed set and yield only under higher soil fertility indicating that limited nutrient availability may constrain pollination benefits. Our study provides evidence for interactions between above- and belowground ecosystem services, highlighting the crucial role of soil fertility in supporting agricultural production not only directly, but also indirectly through pollination. Management strategies aimed at enhancing pollination services might fail in increasing yield in landscapes characterized by high soil service degradation. Comprehensive knowledge about service interactions is therefore essential for the correct management of ecosystem services in agricultural landscapes.

Effects of four cultivation systems for maize on nitrogen leaching .2. Model simulation

Abstract The GLEAMS simulation model (version 2.03) was used to analyse the experimental results presented in M. Borin et al., 1996 (M. Borin C. Giupponi and F. Morari, 1996. Effects of four cultivation systems for maize crop on nitrogen leaching in shallow water. 1. Field experiment. Eur. J. Agron., 5: 295–306) and to derive useful indications on the environmental impacts of the four maize cultivation systems. On the basis of a first test it was found necessary to introduce in the model a subroutine to represent the phenomenon of crack flow (water movement through soil cracks). The modified model (GLEAMS-CF), tested on the experimental data, demonstrated better capability of simulating the field water balance and the nitrogen leaching and was therefore used to simulate the most probable long-term nitrogen leaching that would occur in the various cultivation systems. This was done using a 100-year record created using a climate simulator. This exercise revealed a wide variation in nitrogen leaching caused by the four different cultivation systems studied. Average simulated nitrogen leaching in the four systems were: 85 (system A), 42 (system B), 20.4 (system C) and 19.8 kg ha −1 year −1 (system D).

Time course of biochemical, physiological, and molecular responses to field-mimicked conditions of drought, salinity, and recovery in two maize lines

Drought and salinity stresses will have a high impact on future crop productivity, due to climate change and the increased competition for land, water, and energy. The response to drought (WS), salinity (SS), and the combined stresses (WS+SS) was monitored in two maize lines: the inbred B73 and an F1 commercial stress-tolerant hybrid. A protocol mimicking field progressive stress conditions was developed and its effect on plant growth analyzed at different time points. The results indicated that the stresses limited growth in the hybrid and arrested it in the inbred line. In SS, the two genotypes had different ion accumulation and translocation capacity, particularly for Na+ and Cl−. Moreover, the hybrid perceived the stress, reduced all the analyzed physiological parameters, and kept them reduced until the recovery. B73 decreased all physiological parameters more gradually, being affected mainly by SS. Both lines recovered better from WS than the other stresses. Molecular analysis revealed a diverse modulation of some stress markers in the two genotypes, reflecting their different response to stresses. Combining biochemical and physiological data with expression analyses yielded insight into the mechanisms regulating the different stress tolerance of the two lines.

Estimating evapotranspiration in the Padova Botanical Garden

Abstract. In 1996, intensive building operations near the botanical garden of Padova, the oldest botanical garden in the world, altered a long-established equilibrium between groundwater and plants and threatened the lives of some of them. To avoid water stress, an advanced irrigation system was installed. For design purposes, better knowledge of the water cycle and the monthly average evapotranspiration (ET) in the area was needed. Due to the complex canopy stand of the site, ET was estimated using the water balance method, integrating mathematical models with the Arc/Info Geographical Information System. The water balance was estimated in 1997 and 1998, and results were used to derive an empirical mean crop coefficient of the botanical garden, to simulate the long-term water requirements using the product of reference ET and the apparent crop coefficient to estimate ET from the garden. Two types of hydrological behaviour were identified: one in the central area of the garden, where reduced ground cover diminishes ET and increases runoff and percolation. In the external area, the ET was higher because of the presence of many trees. The empirical mean monthly crop coefficient ranged between 0.56 and 0.83, indicating that ET in the entire area is always less than grass reference ET.

Irrigation automation with heterogeneous vegetation: the case of the Padova botanical garden

An automated control system was set up in the Padova Botanical Garden integrating the information on the soil water status supplied by time domain transmissometry (TDT) sensors with the aid of an irrigation microcomputer. The automatic system consisted of four parts: (a) an irrigation network and electronic control unit (microcomputer); (b) a monitoring system of the soil moisture and water table depth; (c) a management software; and (d) a datalogger connecting sensors to the irrigation microcomputer. Sensors were chosen so that they could be remotely connected through cabling over more than 100 m, guaranteeing adequate accuracy and high reliability over time. To take into account the heterogeneity of plant cover, the site was divided into six irrigation macro-sectors managed separately by the automated system. These macro-sectors were selected by classifying the area on the basis of water requirements, cover type and evapotranspiration demand. The software allowed different irrigation criteria to be defined, considering the values supplied by the moisture sensors singly or on average. In the first year, the automation worked adequately, allowing the irrigation to be managed on the basis of defined thresholds. The irrigation criterion used in the first year for the automated management within macro-sectors, although allowing a favourable water potential to be maintained on average, does not appear to have adequately evaluated the variability of behaviour of the different plants.

Understanding the effects of site-specific fertilization on yield and protein content in durum wheat

Field spatial distribution of yield and protein content, and their interactions with soil and nitrogen (N) fertilisation were studied in an experiment on durum wheat in NE Italy. Using real-time sensors on a combine harvester, it was possible to investigate differences induced by late N foliar spray and nitrogen variable rate applications, and to verify the feasibility of implementing precision harvesting (i.e. harvesting different zones individually to increase grain quality). N fertilisation was ineffective on crop yield since water stress in the last part of the cycle hindered crop growth but had a significant effect on grain protein content. The marked spatial variability observed in the field suggests that site-specific harvesting could be a viable technique to increase wheat quality in the future.

Spatial interpolation quality assessment for soil sensor transect datasets

Near-ground soil sensing improves interpolation of soil properties.Parallel (clustered) transect sampling is generally used on soil-sensor surveys.Unbiased interpolation quality assessment can be achieved using h-block resampling. Near-ground geophysical soil sensors provide valuable information for precision agriculture applications. Indeed, their readings can be used as proxy for many soil parameters. On-the-go soil sensor surveys are, typically, carried out intensively (e.g., every 2m) over many parallel transects. Two types of soil sensors measurements are considered in this paper: apparent electrical conductivity (4 fields in California, USA) and reflectance (1 field in Italy). Two types of spatial interpolations are carried out, universal kriging (model-based) and inverse distance weighting (deterministic). Interpolation quality assessment is usually carried out using leave-one-out (loo) resampling. We show that loo resampling on transect sampling datasets returns overly-optimistic, low interpolation errors, because the left-out data point has values very close to that of its neighbors in the training dataset. This bias in the map quality assessment can be reduced by removing the closest neighbors of the validation observation from the training dataset, in a (spatial) h-block (SHB) fashion. The results indicate that, for soil sensor data acquired along parallel transects: (i) the SHB resampling is a useful tool to test the performance of interpolation techniques and (ii) the optimal (i.e., rendering the same errors of un-sampled locations between transects) SHB threshold distance (h.dist) for neighbor-exclusion is proportional to the semi-variogram range and partial sill. This procedure provides research scientists with an improved means of understanding the error of soil maps made by interpolating soil sensor measurements.

Optimising durum wheat cultivation in North Italy: understanding the effects of site-specific fertilization on yield and protein content

Variable rate fertilization and precision harvesting could increase the potential for meeting durum wheat quality standards. Field spatial distribution of yield and protein content, and their interactions with soil properties and N fertilization were evaluated in an experiment on durum wheat in North Italy in 2011 and 2012. Variable rate fertilization was adopted in three management zones (MZs) with increasing soil fertility, and a foliar N was applied at flowering to investigate differences in protein quantity and quality. During the crop cycle, changes in crop biomass and N status were monitored through NDVI measurement, and grain was sampled in each MZ and gluten proteins extracted at harvest. Spatial variability of yield and protein content was mainly driven by soil texture and base fertilization in both the years, while foliar fertilization was not efficient in enhancing grain protein content. Variable rate fertilization partially mitigated the weather impact; however, unpredictable weather conditions resulted in low N use efficiency. High N rates were confirmed to provide high protein levels and enhance gluten proteins technological quality, but with a risk for the environment. The marked spatial variability in grain quality in terms of total protein and gluten protein content, and the ratio between glutenin/gliadin and high and low-molecular weight glutenin sub-units, suggested the implementation of zone harvesting as a strategy to exploit the positive interaction between grain quality and soil fertility.