Soil Fungi-Plant Interaction

Computer modelling & simulatio

Sustainable apricot orchard management to improve soil fertility and water use efficiency

This 4-year on-farm study reports the effects of different agricultural practices on yield and carbon input in an apricot orchard grown in Mediterranean area. Groups of plants under local orchard management (LOM) practices (i.e., soil tillage, removing of pruning residues, mineral fertilisers) were compared with plots under sustainable orchard management (SOM) actions (i.e., cover crop, no-tillage, compost application, mulching of pruning residues). In the SOM blocks, fertilization was based on plant demand and soil availability and irrigation volumes were calculated on the evapotranspiration values basis, while in the LOM plots fertilization and irrigation were empirically managed. Results show that yield was enhanced by 28% by SOM. In comparison with LOM plots, changed practices increased the amount of N, P, K annually incorporated into soil thus increasing their reservoir in the soil. The study demonstrates that appropriate crop management can increase the mean annual carbon soil inputs from about 1.5 t ha-1 to 9.0 t ha-1 per year

Integration of the regulated deficit irrigation strategy in a sustainable orchard management system

Irrigation in arid regions requires special attention to optimize the management of all components of the orchard system in order to increase water use efficiency and reduce environmental impacts (e.g. soil salinization, degradation of ground and surface waters). This six-year study reports the comparison of some orchard practices (soil and irrigation management, plant nutrition) routinely adopted by local farmers (conventional, C) with those interventions having the potential to save water and maximize water use efficiency in a peach orchard and therefore defined as sustainable (S). Due to the relative approach (C versus S) used in this study, classical statistical comparison of results could not be made. The S system included the application of regulated deficit irrigation (RDI) with specific crop coefficients to calculate the plant water requirement. The S system on average saved 1450 m3 ha-1 of water per year without affecting yield or fruit quality. The concept of economic water productivity (EWP) is discussed. We conclude that addressing some practices currently adopted by farmers could increase sustainability of irrigation and enhance (EWP) in peach tree orchards

Sustainable irrigation in fruit trees

Water management in fruit growing, particularly in areas with high water deficit, low rainfall and limited availability of water for irrigation should aid to save water by: i) the choice of high efficiency irrigation methods and their correct management; ii) the proper choice of the specie, cultivar and rootstock to optimise plant water use; iii) the proper choice of the architecture of the canopy and it's correct management in order to improve water use efficiency; iv) the application of regulated deficit irrigation at growth stages less sensitive to water deficit; v) strengthening the role of technical assistance for a rapid transfer of knowledge to the growers on the sustainable use of water in fruit growing

Soil water availability and relationship between canopy and roots in young olive trees (cv Coratina).

Trials were carried out in the Basilicata region (41°03’ N, 15°42’ E, Southern Italy) using ownrooted plants of the cultivar Coratina planted in 1992 at distances of 6 x 3 m. During 1992, the whole plot (about 7000 m2) was irrigated. From 1993 onwards, irrigation was suspended in part of the plot. A representative number of plants during 1992, 1993, 1994 and 1998 was destroyed in order to carry out dry weight measurements on roots and canopy. The ratio between root and leaf dry weight was always greater in nonirrigated plants compared to irrigated ones. Roots explored a soil volume ranged from 0.5 m3 in the first year to 16.8 m3 in the seventh year for irrigated plants and from 0.5 m3 to 13.4 m3 for non-irrigated ones. The study showed that in deep soil, with a greater capacity for water storage during the rainfall season, limited water supply (220-1350 m3 ha-1) during the first seven years from planting increased canopy growth by 79% compared to nonirrigated plants, but made little difference to root growth. In non-irrigated plants, canopy growth (but not root growth) was drastically reduced, as a defence strategy against water deficit, making for a better root/leaf ratio and consequently greater water availability for leaves

Transpiration and calcium accumulation in apricot fruit

The seasonal variation of transpiration rate and accumulation of calcium (Ca) in fruit of apricot (Prunus armeniaca L.) are presented. Midday transpiration rate (open system ADC-LCA4) was higher just after fruit-set peaking at about 0.5 mmol m-2 s-1; thereafter it declined and reached the lowest value three weeks later. In parallel, Ca was linearly accumulated within the early four weeks of fruit development reaching 80% of the final content. Afterwards it slowly increased and reached about 6 mg per fruit at harvest time. Results suggest that transpiration decline can be held to account for the early cessation of Ca import into the fruit. Opportunities for field manipulation to increase fruit Ca content are discussed

Does dye infusion indicate xylem functionality in kiwifruit?

This study was undertaken to establish whether the rate of uptake of an aqueous solution by the fruitstalks of detached Actinidia deliciosa fruits (‘Hayward’) correlates with fruit xylem functionality assessed by dye infusion. Fruits were collected from the orchard, pre-dawn and 65 days after bloom. In the laboratory the fruitstalks were re-cut under water and their outsides lightly smeared with Vaseline before placing their cut ends in small, pre-weighed (W1) (mg) vials of dye solution. Fruits were allowed to take up dye solution for ~100 min (T) under uniform aerial conditions. Fruits were then sliced 1/5 way up from the stalk end and the fraction (F) (%) of stained bundles was determined. The residual dye solution was weighed (W2) (mg) and the solution uptake rate (U) (mg/min) determined per unit of fruit surface area (S) as U=(W1-W2)/(S×T). Analysis reveals that F is linearly related to U (R2 = 0.81). The suitability of the stain infusion technique for assessing xylem functionality is discussed

Measuring sap flow through small diameter stems

Most techniques for measuring xylem sap flow involve the use of heat as a tracer, and the insertion of linear probes radially into the secondary xylem. The disruption caused means probe based techniques can generally only be used with stems larger than approximately 10 mm in diameter. For smaller diameter stems, constant power heat balance gauges are available, but they can be difficult and expensive to use, and may not resolve very small flows. As part of our studies of kiwifruit fruit development we need to better understand factors affecting the movement of water and solutes into and out of the fruit via the pedicel. There are also many other potential applications for measurement of sap flow through small diameter stems and roots. We therefore set out to develop gauges capable of measuring sap flow in both directions through stems as small as 1 mm in diameter. We describe a modification of the ‘heat ratio’ heat pulse technique. Instead of probes as heating and sensing elements, a chip resistor is used as a miniature heater, and both the heater and temperature sensing thermocouples are pressed against the surface of the stem. For calibration, excised Actinidia deliciosa fruit pedicels were connected to a pressurized water supply and actual flow measured gravimetrically. Heat pulse velocity measured using the gauge was linearly related to actual sap flow in both the acropetal and basipetal directions. On intact fruit pedicels the gauges were used to measure sap flow into Actinidia fruit from shoot, and from the fruit to the shoot when the shoot was allowed to dehydrate. Development of the technique is continuing with further calibration and modelling of the propagation of the heat pulse through the bark, phloem and xylem