The effects of iron (Fe) deficiency on fruit yield and quality were measured in two peach cultivars, Carson (yellow-skin fruit) and Babygold (red-skin fruit). In both cultivars, Fe deficiency caused major decreases in fruit fresh weight per tree and number of fruits per tree. Fruits from Fe-deficient peach trees had a smaller size, resulting in a large decrease in the percentage of commercially acceptable fruits, whereas fruit firmness was unaffected. In cv. Babygold, Fe deficiency greatly decreased the red color of the fruit skin. Part of these results was likely associated with a delay in fruit ripening. When fruits with similar appearance were compared, taking into account fruit size, color, and firmness, Fe deficiency generally led to higher concentrations of organic anions (especially succinate and quinate), vitamin C, and phenolic compounds and to lower total sugar/total organic acid ratios. This could lead to decreased fruit eating quality and to a slight improvement in fruit nutritional value.

Ballistic simulation of the spray sprinkler for self-propelled irrigation machines requires the incorporation of the effect of the jet impact with the deflecting plate. The kinetic energy losses produced by the jet impact with the spray plate were experimentally characterized for different nozzle sizes and two working pressures for fixed spray plate sprinklers (FSPS). A technique of low speed photography was used to determine drop velocity at the point where the jet is broken into droplets. The water distribution pattern of FSPS for different nozzle sizes, working at two pressures and under different wind conditions were characterized in field experiments. The ballistic model was calibrated to simulate water distribution in different technical and meteorological conditions. Field experiments and the ballistic model were used to obtain the model parameters (D50, n, K1and K2). The results show that kinetic energy losses decrease with nozzle diameter increments; from 80% for the smallest nozzle diameter (2 mm) to 45% for nozzle diameters larger than 5.1 mm, and from 80% for the smallest nozzle diameter (2 mm) to 34.7% for nozzle diameters larger than 6.8 mm, at 138 kPa and 69 kPa working pressures, respectively. The results from the model compared well with field observations. The calibrated model has reproduced accurately the water distribution pattern in calm (r=0.98) and high windy conditions (r=0.76). A new relationship was found between the corrector parameters (K1’ and K2’) and the wind speed. As a consequence, model simulation will be possible for untested meteorological conditions.

Reducing the working pressure at the sprinkler nozzles is one of the alternatives to reduce energy requirements in solid-set sprinkler irrigation systems. Previous studies reported ≈10% lower seasonal Christiansen uniformity coefficient (CUC) for lowpressure treatments than for standard treatments, but no differences in maize yield. This research analyses the effect of maize canopy water partitioning on irrigation performance indexes (CUC and wind drift and evaporation losses, WDEL). Three irrigation treatments were considered, based on the working pressure: 1) A standard brass impact sprinkler operating at a pressure of 300 kPa (CIS300); 2) A standard brass impact sprinkler operating at a pressure of 200 kPa (CIS200); and 3) A modified plastic impact sprinkler (with a deflecting plate attached to the drive arm) operating at a Agricultural Water Management 203: 353-365 (2018) 2 pressure of 200 kPa (DPIS200). Irrigation performance was measured using a catch-can network located above the maize canopy (CUCac, WDELac) along the whole crop season and using stemflow and throughfall devices below the maize canopy (CUCbc, WDELbc) in eight irrigation events. Maize growth, yield and its components were measured.Under low-wind and fully developed canopy conditions (a frequent situation for maize irrigation), CUCbc resulted higher than CUCac for the low-pressure treatments, while the opposite was observed for the standard pressure treatment. Maize canopy partitioning reduces the differences in irrigation performance indexes between pressure treatments, explaining why there are no differences in grain yield between them. Caution should be used when measuring sprinkler irrigation performance above tall canopies, since the elevation of the catch-cans and the crop canopy partitioning affect performance estimations.

Laboratory-scale cone penetration tests (CPTs) in silt were performed with x-ray micro tomography and analysed with three-dimensional digital image correlation. During insertion of the instrumented probe, these tools allow the identification of a contractant bulb of silt close to the tip of the probe surrounded by a larger bulb of dilating material. The results obtained (in particular the failure mechanisms observed) shed new light on the mechanics of cone penetration in silt and consequently reflect on the interpretation of in situ CPTs.