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In addition to the weather conditions, agronomic practices can have a major influence on maize crop yield and contamination with mycotoxins. In this work, the effect of different irrigation systems (flood vs. sprinkler irrigation), sprinkler irrigation management (low vs. high frequency, daytime vs. nighttime irrigation) and tillage practices (conventional tillage, no tillage with or without crop stover) on crop yield and the contamination with aflatoxins (AFs), fumonisins (FUM) and deoxynivalenol (DON) were evaluated in the maize grain from two experimental maize fields. No aflatoxins were detected in any of the samples analyzed. DON and FUM levels were significantly higher when the sprinkler irrigation was performed at nighttime (0.54 and 1.21 mg kg−1, respectively) as compared to daytime (0.38 and 0.45 mg kg−1). Likewise, DON and FUM were greater when irrigation frequency was low (0.61 and 1.09 mg kg−1, respectively) in comparison with high frequency (0.30 and 0.57 mg kg−1). DON concentrations were significantly higher in fields with sprinkler irrigation (0.53 mg kg−1) as compared to flood irrigation (0.19 mg kg−1), while the levels of FUM were very similar regardless of the maize irrigation system. Mycotoxin concentrations were not affected by the different soil tillage practices. This highlights the importance of implementing crop management practices to minimize the risk of mycotoxin contamination in maize. [ABSTRACT FROM AUTHOR]

The magnitude and duration of corn transpiration reduction during center-pivot sprinkler irrigation was analyzed on a commercial plot. The irrigation event was defined as the period during which the pivot arm was passing over the transect AC and water droplets were moistening the plants (moist treatment). Corn transpiration rates were measured at three spots of that transect and simultaneously at another spot (dry treatment) located approximately 270 m east from the transect AC. Corn transpiration rates for the moist treatment location were reduced by 30-36% compared to the dry treatment location during the irrigation event. After irrigation, the transpiration reduction lasted for 1.8-2.6 h, and ranged from 22-29%. The gross wind drift and evaporation losses ranged from 10-13% of the applied water, whereas the net interception losses were 2% of the applied water. Considering the observed corn transpiration reduction during and after the irrigation, the net sprinkler evaporation losses ranged from 11-13% of the applied water, with no relevant differences along the pivot arm. [ABSTRACT FROM AUTHOR]

Abstract: The microclimatic (air temperature and vapor pressure deficit (VPD)) and physiological (canopy temperature and plant transpiration) changes due to center pivot sprinkler irrigation were monitored at a commercial plot of maize (Zea mays L.). Two treatments were considered: (a) moist, measurements taken at three spots on a transect when the pivot was running over it; (b) dry, measurements taken simultaneously at a fourth spot D, 270m apart. A total of 34 irrigation events were monitored, seven of which included plant transpiration measurements. For the transpiration-measured irrigation events, significant (P =0.05) reductions in the monitored variables for the moist treatment were observed for 0.6–2.1h before, during and 0.5–2.4h after the irrigation. The average decreases for the phase during were 1.8–2.1°C for air temperature, 0.53–0.61kPa for VPD, 3.1–3.8°C for canopy temperature, and 0.22–0.28mmh−1 (30–36%) for transpiration. Lower reductions were found for the phases before and after. The duration of the microclimatic changes decreased as the distance from the center of the pivot increased (from 3.9 to 2.2h), but the duration of the physiological changes was similar in the different pivot arm portions (≈4h). Microclimatic and physiological changes were higher in drier and warmer days. Transpiration reduction due to irrigation was higher as closer to the center of the pivot and represented 5–7% of the applied water. The estimated reduction of ET represented 1.5–1.8% of the applied water. The reduction of transpiration and ET is positive because it represents a reduction in irrigation requirements. The decrease in maize canopy temperature could be positive or negative depending on its effect on photosynthesis. [Copyright &y& Elsevier]

• Soil tillage and irrigation system affected soil CO 2 emissions. • A threshold value at 60 % WFPS was found for soil CO 2 fluxes under flood irrigation. • No-tillage systems reduced cumulative CO 2 emissions by 30 %. • Sprinkler irrigation increased cumulative CO 2 emissions and total aboveground biomass. • Soil acted as a sink of CH 4 throughout the measurement period. Irrigation as well as soil tillage management are considered two possible strategies to reduce carbon dioxide (CO 2) and methane (CH 4) emissions from the soil in Mediterranean agroecosystems. The objective of this work was to assess the impact of the irrigation system (i.e. flood, F; and sprinkler, S) and the soil tillage system (i.e. conventional tillage, CT; no-tillage maintaining the maize stover, NTr; and no-tillage removing the maize stover, NT) on CO 2 and CH 4 emissions from the soil during three growing seasons (2015, 2016 and 2017) and two fallow periods between growing seasons (15–16 fallow and 16–17 fallow) in a maize (Zea mays L.) monoculture system. Soil temperature and water-filled pore space (WFPS) had a great influence on daily soil CO 2 fluxes but not on daily soil CH 4 fluxes. In all tillage-irrigation treatments, daily soil CO 2 fluxes showed an increase with soil temperature, being this increment greater when soil temperature was above 15 °C in coincidence with the maize plant growth. In contrast, soil WFPS differently affected daily soil CO 2 fluxes depending on the irrigation system. Under S irrigation, daily soil CO 2 fluxes increased with soil WFPS, whereas under F irrigation a threshold value of 60% WFPS was found, with a positive or negative effect on CO 2 fluxes for values below or above this threshold value, respectively. Over the three maize growing seasons, CT-S presented the greatest cumulative soil CO 2 emissions with a seasonal average value of 3.28 Mg CO 2 -C ha−1. In contrast, for the same period, NTr-S cumulative soil CO 2 emissions were up to 42% lower than the CT-S cumulative soil CO 2 emissions. Cumulative CH 4 emissions were only affected by soil tillage during the 16–17 fallow period, resulting both NTr and NT in greater net CH 4 uptake compared with CT. This work highlights the importance of irrigation and soil tillage systems as key agricultural practices to minimize soil CO 2 and CH 4 emissions under Mediterranean conditions. [ABSTRACT FROM AUTHOR]

A comparison between experimental and simulated data, considering the Priestley–Taylor (PT) and Penman–Monteith (PM) reference-evapotranspiration (ET0) approaches was carried out. Experimental data, obtained from an irrigation assessment, conducted during the 1995 and 1996 maize growth-seasons at Zaragoza, Spain, was compared to the mechanistic-model SWAP simulation-results, considering each of the ET0 calculation approaches in the model input. Soil hydraulic properties, meteorological data, seeding and harvest dates, crop water management and other experimental data were used as SWAP input. As corresponding to the windy and dry conditions found in many Mediterranean landplanes, PT-ET0 values were significantly lower than PM-ET0 calculations. Furthermore, simulated actual evapotranspirations considering the PT approach (PT-ETc) were lower than those found in the simulations that consider the PM approach (PM-ETc). Correspondingly, simulated drainage flux and soil water contents were higher when the PT-ET0 approach was used. The correlation coefficients between simulated and measured actual maize evapotranspirations and soil water contents were statistically significant, but the same for both ET0 calculation approaches. Mean and median differences between actual and simulated maize water-use were not statistically different from zero for both considered ET0 calculation approaches. Experimental data variability was significantly higher than simulated variability. The comparisons among the evaluated irrigation options, made with the experimental water-use data, lead almost to the same conclusions than those achieved from the simulated maize water-use. Considering PM-ETc rather than PT-ETc yields no statistical difference in the modeling-based conclusions. According to the obtained results, the PT approach could be used under Mediterranean conditions for comparative assessments aimed to support irrigation decision-making. [Copyright &y& Elsevier]