A. Pérez-Pastor

Physiological responses of apricot plants grafted on two different rootstocks to flooding conditions

The authors are grateful to Dr Pedro Rodriguez from INCA (La Habana, Cuba) for help with the root hydraulic conductivity measurements. The study was supported by CICYT (HID1999-0951; AGL2000-0387-C05-04) grants to the authors.

Gas exchange and water relations of young apricot plants under drought conditions

The authors are grateful to J. Soto-Montesinos, M.D. Velasco, M. Garcia and E. Nicolas for their assistance. The study was supported by CICYT (AMB95- 0071) and Consejeria de Medio Ambiente, Agricultura y Agua de Murcia grants to the authors.

Almond agronomic response to long-term deficit irrigation applied since orchard establishment

This study assesses the long-term suitability of regulated (RDI) and sustained deficit irrigation (SDI) implemented over the first six growing seasons of an almond [Prunus dulcis (Mill.) D.A. Webb] orchard grown in a semiarid area in SE Spain. Four irrigation treatments were assessed: (i) full irrigation (FI), irrigated to satisfy maximum crop evapotranspiration (100% ETc); (ii) RDI, as FI but receiving 40% ETc during kernel-filling; (iii) mild-to-moderate SDI (SDImm), irrigated at 75–60% ETc over the entire growing season; and (iv) moderate-to-severe SDI (SDIms), irrigated at 60–30% ETc over the whole season. Application of water stress from orchard establishment did not amplify the negative effects of deficit irrigation on almond yield. Irrigation water productivity (IWP) increased proportionally to the mean relative water shortage. SDIms increased IWP by 92.5%, reduced yield by 29% and applied 63% less irrigation water. RDI and SDImm showed similar productive performances, but RDI was more efficient than SDImm to increase fruiting density and production efficiency (PE). We conclude that SDIms appears to be a promising DI option for arid regions with severe water scarcity, whereas for less water-scarce areas RDI and SDImm behaved similarly, except for the ability of RDI to more severely restrict vegetative development while increasing PE.

Long-term impact of deficit irrigation on the physical quality of berries in 'Crimson Seedless' table grapes.

BACKGROUND In table grapes, berry firmness influences consumer acceptance so it is important to avoid berry shattering and dehydration during their post-harvest life. Since studies of irrigation effects on table grape quality are comparatively rare, sensory evaluation aimed to identify high-quality berries obtained under different deficit irrigation treatments. A 3-year study examined the effects of deficit irrigation strategies on some physical quality attributes at harvest, after 28 days of cold storage at 0 °C and after an additional shelf-life period of 3 days at 15 °C. Control vines were irrigated to ensure non-limiting water conditions (110% of crop evapo-transpiration), while both regulated deficit irrigation treatment (RDI) and partial root-zone drying (PRD) treatments applied 35% less water post-veraison. The null irrigation treatment (NI) only received natural precipitation (72% less water than control vines). RESULTS Total yield and physical quality at harvest were not significantly affected by RDI or PRD. Only severe deficit (NI) decreased berry size, and this treatment had the most dehydrated berries and the worst sensory scores post-harvest. After cold storage, increased berry shattering of the PRD treatment was correlated with lower leaf xylem abscisic acid (ABA) concentration at the time of harvest. Overall quality, especially stem browning, determined the shelf-life, and longer storage duration tended to diminish treatment differences. CONCLUSIONS Only NI clusters showed lower quality than their irrigated counterparts. Neither RDI nor PRD had any noticeable effect on berry quality at the end of cold storage and shelf-life, with the slight differences detected between these treatments related to stem browning and dehydration. Sensory results were similar in RDI and PRD, which provided grapes that were more acceptable to consumers than the control. Thus, it is possible to decrease irrigation of table grapes without adversely affecting the physical quality of the berries.

Combined effects of deficit irrigation and fresh-cut processing on quality and bioactive compounds of nectarines

Falagan N., Artes F., Gomez P.A., Artes-Hernandez F., Perez-Pastor A., de la Rosa J.M., Aguayo E. (2015): Combined effects of deficit irrigation and fresh-cut processing on quality and bioactive compounds of nectarines. Hort. Sci. (Prague): 42: 125–131. Water scarcity makes necessary the use of tools for increasing water productivity such as regulated deficit irrigation strategies (RDI). The effect of RDI on fresh-cut white flesh extra-early nectarine was studied. Initially, the soluble solids content of nectarines from RDI was higher than in control and over-irrigated fruits (9.72 ± 0.20 vs. 8.57 ± 0.05°Brix, respectively) but after shelf-life storage no differences were found. During storage, RDI fruits had a more stable antioxidant capacity and soluble phenolic content. This treatment showed 10% more vitamin C than the other irrigation treatments, due to an increase in dehydroascorbic acid content. No pathogenic bacteria growth was found and all microbial counts were below the European legal limits. For all the irrigation treatments, the final sensorial scores were above the limit of marketability. Overall, RDI enabled savings of about 1,260 m3 of water/ha and year, without negatively affecting the quality of the fruit, allowing for their use as a fresh-cut product with a shelf-life of 8 days at 5°C.

Greenhouse gas emissions and soil organic matter dynamics in woody crop orchards with different irrigation regimes

Water scarcity in arid, semiarid and dry regions is a limiting factor for the development of sustainable agriculture. As a consequence, the adoption of new strategies such as regulated deficit irrigation (RDI) to reduce water and energy consumption will be essential. Decreases in irrigation water content may also have positive effects on soil C cycle. Thus, an experiment was setup in three woody crop orchards during two years, with the objective of assessing if RDI can reduce soil CO2 and N2O emissions, modify soil inorganic C and organic C quality and stability and affect soil aggregation. Soil CO2 and N2O emissions were measured every two weeks while soil samplings were carried out every three months. Results indicated that decreases in soil moisture by RDI implementation were related to significant decreases in CO2 emissions in all crops. RDI contributed to an average decrease, compared with full irrigation, of 1088-1664 g CO2 m-2 in the experimental period. Furthermore, CO2 emission was negatively correlated with inorganic C, suggesting the protective effect of soil carbonates towards organic matter. RDI also contributed to significantly decrease soil N2O emissions. However, N2O emission patterns did not directly follow soil moisture patterns and were constant in the experimental period. RDI contributed to an average decrease, compared with full irrigation, of 90-409 mg N2O m-2. No physicochemical property was significantly affected by irrigation regime. Although microbial biomass was not significantly affected by RDI, β-glucosidase activity was significantly higher under full irrigation during the warm seasons, with significant positive correlation with CO2 emissions. This seems to suggest that a significant fraction of CO2 emitted from soil derives from organic matter degradation, which is limited with low water content. So, RDI could contribute to promote soil C sequestration by reduced greenhouse gas emissions, with no negative effects on soil structure at short-term.