Antonio Berti

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.

Estimation of economic thresholds for weed control in soybean (Glycine max (L.) Merr.)

Abstract The competitive ability of 10 major soybean weeds (Abutilon theophrasti Medicus (ABUTH), Amaranthus cruentus L. (AMACR), Chenopodium album L. (CHEAL), Datura stramonium L. (DATST), Panicum miliaceum L. (PANMI), Polygonum persicaria L. (POLPE), Setaria viridis (L.) Beauv. (SETVI), Solanum nigrum L. (SOLNI), Sorghum halepense (L.) Pers. (SORHA), Xanthium strumarium L. (XANST)) was studied for two years in northern Italy. The economic thresholds for soybean weed control have been determined for different herbicides and mixtures. Economic thresholds were very low in 1989, when only SOLNI and PANMI showed a threshold higher than 1 plant m−2, while in 1990, values varied between 0.05 plants m−2 for XANST and 4.3 plants m−2 for ABUTH. The seed production — weed density relationships for five species (ABUTH, AMACR, CHEAL, DATST and XANST) were also determined and the long-term evolution of the potential infestations deriving from subeconomic threshold populations were calculated. The results of the calculation demonstrate the inadequacy in the medium-long-term of weed control decisions based on single year economic thresholds.

Application of decision-support software for postemergence weed control

Abstract GESTINF is a decision tool for postemergence weed control based on the equivalent density approach. Using observed weed densities just before treatment, the program estimates the economic return from the treatment, thus indicating whether to treat or not and, if a treatment is needed, the most economical weed control solution. Each treatment is also characterized by an environmental pollution index. GESTINF has been tested in wheat and soybeans on a farm in northeastern Italy with a total cropping area of 60 ha of wheat and 40 ha of soybean. For both crops, weed control followed the suggestions of GESTINF, whereas the remaining cropped areas were treated according to standard farm weed control practices. To compare the two weed control systems, weed control efficacy, average crop yield, and the extra time required for scouting and treatments were measured. In both crops, the treatments suggested by GESTINF showed good efficacy, and yields proved to be no different from those obtained in the fields treated with standard farm weed control practices. In most cases, GESTINF selected treatments with a lower environmental effect. The most critical point was the time required to scout the weed population that, in low-value crops or when very cheap treatments were available, reduced the weed control economic return. In wheat, GESTINF indicated that fewer fields needed to be treated than did the conventional system. However, extra costs due to both scouting and more expensive treatments balanced the savings obtained from nontreated areas. For soybean, the treatments adopted by the farm were based on a combination of pre- and postemergence practices. In this case, GESTINF identified cheaper but still efficacious treatments, significantly reducing the total cost of weed control. Nomenclature: Soybean, Glycine max (L.) Merr.; wheat, Triticum aestivum L.

A Dynamic Method for Gap Filling in Daily Temperature Datasets

AbstractA regression-based approach for temperature data reconstruction has been used to fill the gaps in the series of automatic temperature records obtained from the meteorological network of Veneto Region (northeastern Italy). The method presented is characterized by a dynamic selection of the reconstructing stations and of the coupling period that can precede or follow the missing data. Each gap is considered as a specific case, identifying the best set of stations and the period that minimizes the estimated reconstruction error for the gap, thus permitting a potentially better adaptation to time-dependent factors affecting the relationships between stations. The best sampling size is determined through an inference procedure, permitting a highly specific selection of the parameters used to fill each gap in the time series. With a proper selection of the parameters, the average errors of reconstruction are close to 0 and those corresponding to the 95th percentile are typically around 0.1°C. In compari...

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.

ECONOMICS OF HERBICIDE USE ON ARABLE CROPS IN NORTH-CENTRAL ITALY

Abstract The frequency distribution of yield loss due to weeds in winter wheat, sugar beet, maize and soybean has been studied using the available data of weed control trials undertaken in north-central Italy in the last 30 years. The breakeven yield loss and the probability of obtaining a positive net return from chemical weed control were calculated, considering different treatment options and different weed-free yields. The mean value of yield loss varies from 23 to 30% in winter wheat and from 33.9 to 37.5% in maize, depending on the type of weed flora, and is 50.2% for sugar beet and 33.3% for soybean. The breakeven yield loss falls between 1.4 and 15% in winter wheat, 4.0 and 12.2% in maize, 5.1 and 12.6% in sugar beet and 3.3 and 17.7% in soybean. Even with the higher treatment costs and the lower yields, the probability of a positive net return is always > 80% and, for sugar beet, > 95%.

Qualitative and quantitative response of soil organic carbon to 40 years of crop residue incorporation under contrasting nitrogen fertilisation regimes

Crop residue incorporation (RI) is recommended to increase soil organic carbon (SOC) stocks. However, the positive effect on SOC is often reported to be relatively low and alternative use of crop residues, e.g. as a bioenergy source, may be more climate smart. In this context, it is important to understand: (i) the response of SOC stocks to long-term crop residue incorporation; and (ii) the qualitative SOC change, in order to judge the sustainability of this measure. We investigated the effect of 40 years of RI combined with five different nitrogen (N) fertilisation levels on SOC stocks and five SOC fractions differing in turnover times on a clay loam soil in Padua, Italy. The average increase in SOC stock in the 0–30cm soil layer was 3.1Mgha–1 or 6.8%, with no difference between N fertilisation rates. Retention coefficients of residues did not exceed 4% and decreased significantly with increasing N rate (R2=0.49). The effect of RI was higher after 20 years (4.6Mgha–1) than after 40 years, indicating that a new equilibrium has been reached and no further gains in SOC can be expected. Most (92%) of the total SOC was stored in the silt and clay fraction and 93% of the accumulated carbon was also found in this fraction, showing the importance of fine mineral particles for SOC storage, stabilisation and sequestration in arable soils. No change was detected in more labile fractions, indicating complete turnover of the annual residue-derived C in these fractions under a warm humid climate and in a highly base-saturated soil. The applied fractionation was thus useful to elucidate drivers and mechanisms of SOC formation and stabilisation. We conclude that residue incorporation is not a significant management practice affecting soil C storage in warm temperate climatic regions.

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.

Modeling of Glyphosate Application Timing in Glyphosate-Resistant Soybean

Abstract The introduction of herbicide-resistant crops and postemergence herbicides with a wide action spectrum shifted the research focus from how to when crops should be treated. To maximize net return of herbicide applications, the evolution of weed–crop competition over time must be considered and its effects quantified. A model for predicting the yield trend in relation to weed removal time, considering emergence dynamics and density, was tested on data from glyphosate-resistant soybean grown in cropping systems in Italy and Argentina. Despite an ample variation of weed emergence dynamics and weed load in the four trials, the model satisfactorily predicted yield loss evolution. The estimated optimum time for weed control (OTWC) varied from about 18 d after soybean emergence in Argentina to 20 to 23 d in Italy, with time windows for spraying ranging from 14 to 28 d. Within these limits a single glyphosate application ensures good weed control at low cost and avoids side effects like the more probable unfavorable weed flora evolution with double applications and the presence of residues in grains. Despite the apparent simplicity of weed control based on nonselective herbicides, the study outlines that many variables have to be considered to optimize weed management, particularly for the time evolution of the infestation and, subsequently, a proper timing of herbicide application. Nomenclature: Glyphosate; soybean, Glycine max (L.) Merr., ‘Asgrow ASRR19’, ‘Asgrow XP2101R’, ‘Asgrow 6401’.

Evaluation of the cost-risk relationship of groundwater contamination in weed control of soybean

Abstract The relationship between weed control cost in soybean and the risk of groundwater contamination was evaluated for five typical pedo-floristic situations of the Po Valley. For the weed control treatments, a ‘GroundWater Danger Index’ (GWDI) was calculated as the proportion of the active ingredient applied which leaches downwards, relative to the guidelines for drinking water calculated according to the World Health Organisation methodology. The fraction of the active ingredient which can leach was estimated with the Pesticide Root Zone Model (PRZM) and by means of the Attenuation Factor (AF) and the Groundwater Ubiquity Score (GUS). For each chemical option a total cost was calculated adding the treatment cost to the value of the yield loss caused by residual weeds. The optimal treatments were very different depending on the pedo-climatic and floristic situations. A large number of options had higher values of GWDI than those of atrazine under the same conditions, indicating a potential risk of groundwater contamination in soybean weed control. The GWDI calculated with the PRZM were then compared to those obtained with the other simplified indices, AF and GUS. Using the AF gave a good correlation with the values obtained on the basis of the PRZM, while with GUS the correlation, even where significant, was poor.