Root aeration improves yield and water use efficiency of tomato in heavy clay and saline soils

Water logging and salinity of the soil alter both the physical and biological environment of plant roots. In two experiments, we investigated the effects of imposed aeration on yield and the physiological response of tomato (Lycopersicon esculentum L.) variety Improved Apollo growing under protected conditions over a range of salinities (the salinity experiment), and under constant field capacity (FC) or drier soil conditions (the moisture experiment). Subsurface irrigation with aerated water (12% air in water) stimulated above-ground growth, and enhanced the reproductive performance through earliness for flowering and fruiting compared with the control. Fruit yield of tomato with aeration in the moisture experiment was increased by 21% compared with the control (4.2 kg versus 3.7 kg per plant), and the effect of aeration on fruit yield was greater in FC than in the drier treatment. Fruit yield was increased by 38% in saline soil due to aeration compared with the non-aerated control. Increasing salinity from 2 to 8.8 dS m⁻¹, and 10 dS m⁻¹ reduced fruit yield by 18% and 62%, respectively, but 4 dS m⁻¹ did not suppress yield. Aeration in both the experiments increased plant water use and water use efficiency (WUE), expressed as weight per unit of applied water. Biomass WUE was greater by 16% and 32% in the moisture and salinity experiments, respectively. The increased yield with aeration was also accompanied by an increased harvest index (HI) defined as the proportion of dry fruit biomass to total dry biomass, greater mean fruit weight, high fruit DM, and increase in leaf chlorophyll content and shoot: root ratio, and a reduced water stress index (computed from the difference between air and leaf temperature). The benefit gained from aerating irrigation water was not only observed under conditions where air-filled porosity may be low (e.g., in poorly structure sodic soils, or at field capacity in clay soils), but also in drier soils.     

Responses of pepper to deficit irrigation for paprika production

Pepper (Capsicum annuum L.) production is normally carried out under irrigation as the crop is very susceptible to water shortage. Deficit irrigation strategies in pepper for paprika could increase production and facilitate mechanical harvest and, at the same time, save water. We conducted a field experiment that imposed water deficits, either during ripening (T1) or throughout the season (T2), and compared them to a fully irrigated control (T3). Stem water potential varied from −0.6 MPa in T3, early in the season to −1.5 MPa in T2 prior to harvest. Applied irrigation water for T1, T2, and T3 was 456, 346 and 480 mm, respectively. Water deficits depress leaf area and biomass production but did not affect the proportion of flowers that set fruit. Dry fruit weight in T2 at harvest was 66% of T3, but did not differ significantly between T1 and T3. However, commercial yield (based on colour production) was significantly higher in T3 than in the other two treatments, as the late water deficits imposed in T1 delayed harvest. We concluded that water deficits, either sustained or applied at fruit ripening, required for mechanical harvest do not hasten ripening and are detrimental to commercial yields and that pepper plants should be well supplied with water until harvest for maximum paprika production.     

Effect of different biodegradable and polyethylene mulches on soil properties and production in a tomato crop

The use of plastic materials for mulching is a very common practice for vegetable crops. Black polyethylene is the most widely used due to its excellent properties and low cost. However, the massive use of these materials supposes an environmental risk. In the last few years, the use of starch-based biodegradable films has been introduced as an alternative to conventional mulches. These materials can be incorporated into the soil at the end of the crop season and undergo biodegradation by soil microorganisms. A 2-year study was conducted to determine the response of a tomato crop to seven mulch materials (polyethylene and biodegradable) in open fields in Central Spain. Biodegradable films underwent early decomposition, but in general remained functional during use and did not affect yield and the fruit quality attributes (total soluble solids, firmness, dry weight, juice content and shape). The temperatures reached under polyethylene films were always higher than under biodegradable films, which could be a disadvantage in certain circumstances, especially in hot climates, although may be advantageous in cool conditions. The use of polyethylene films resulted in the lowest values of soil microbial biomass C and soil organic matter mineralization, probably due to the increase of temperature registered under mulches. The analysis of the marketable yield components indicates that the variability in yield mainly depended on the number of fruits, with mean fruit weight being practically constant in the different treatments and seasons, which suggests the strong varietal character of this parameter.     

Effects of water deficit on the vegetative response,yield and oil quality of olive trees (Olea europaea L., cv Coratina) grown under intensive cultivation

An experiment was carried out in a young high-density olive grove (556 plants ha⁻¹—Olea europaea L., cv Coratina) located in Southern Italy to evaluate the effect of different soil water availability on the vegetative and productive performances of olive trees also looking into the quality of the resulting oils. Trials were carried out over a 3-year period on trees subjected to irrigation and grown under rainfed conditions. Vegetative tree response, as shoot elongation and trunk diameter, was evaluated. Yield per plant, fruit characteristics, oil quality indices (free fatty acid content, peroxide value, UV adsorption at 232 and 270 nm, total phenols, α-tocopherol content) were determined for both irrigated and non-irrigated treatments in the ‘on’ years 1997 and 1999 (6th and 8th year after planting, respectively).     

Effects of soil water availability on development of suberin lamellae in the endodermis and exodermis and on cortical cell wall thickening in red bayberry (Myrica rubra Sieb. et Zucc.) tree roots

The effects of soil water availability on suberin lamellae formation in the endodermis and exodermis and the occurrence of cell wall thickening in the cortex in red bayberry (Myrica rubra Sieb. et Zucc.) tree roots were examined during tissue aging. For several months, red bayberry trees were grown in small baskets under dry, normal, and waterlogged soil water conditions. Transverse sections of roots from 5 mm from the tip to the basal portion were stained with several staining solutions and the cell structure was observed. Root anatomical development was significantly changed by soil water conditions. The suberin lamellae in the endodermis formed later in plants grown under dry conditions than in those grown under waterlogged conditions. Cell wall thickening in the cortex near the endodermis was promoted by drought, but apparently not by waterlogged conditions.