Plant water status indicators for detecting water stress in pomegranate trees

Measurements obtained by the continuous monitoring of trunk diameter fluctuations were compared with discrete measurements of midday stem water potential (stem) and midday leaf conductance (gl) in adult pomegranate trees (Punica granatum (L.) cv. Mollar de Elche). Control plants (T0) were irrigated daily above their crop water requirements in order to attain non‐limiting soil water conditions, while T1 plants were subjected to water stress by depriving them of irrigation water for 34 days, after which time irrigation was restored and plant recovery was studied for 7 days. T1 plants showed a substantial degree of water stress, which developed slowly. Maximum daily trunk shrinkage (MDS) was identified to be the most suitable plant‐based indicator for irrigation scheduling in adult pomegranate trees, because its signal:noise ((T1/T0):coefficient of variation) ratio was higher than that for stem ((T1/T0):coefficient of variation) and gl ((T0/T1):coefficient of variation). MDS increased in response to water stress, but when the stem fell below −1.67 MPa, the MDS values decreased.This research was supported by CICYT/FEDER (AGL2010‐19201‐C04‐01AGR) and AECID (A1/035430/11) grants to the authors. AG, JCG and ZNC were funded by a FPU, a FPI and a AECID grant, respectively

Effect of preharvest fruit bagging on fruit quality characteristics and incidence of fruit physiopathies in fully irrigated and water stressed pomegranated trees

BACKGROUND: This report studied the response of pomegranate fruit under full irrigation (FI) and water stress (WS) conditions to bagging with externally glossy single layer cellulosic paper bags open at the bottom from the end of fruit thinning to harvest time. RESULTS: Bagging decreased fruit size and the maturity index, and increased antioxidant activity in FI conditions. Moreover, fruit bagging substantially reduced the incidence of peel sunburn in both irrigation conditions. CONCLUSION: The delay in fruit growth and ripening as a result of pomegranate fruit bagging is outweighed by the very important commercial benefit in terms of the reduced incidence of peel sunburn and the increase in fruit antioxidant activity

Regulated deficit irrigation in table olive trees during a sensitive period

Olive tree is one of the most important irrigated fruit at Spain (around 400.000 ha). The water needs in olive orchard are greater than the water availability. Therefore, deficit conditions are common at the field. The aim of this work is to study a regulated deficit irrigation (RDI) scheduling based on midday stem water potential (Y) that limits irrigation before harvest. The experiment was performed at La Hampa experimental farm (Coria del río, Seville, Spain) in 45 years-old olive (cv Manzanillo). Three irrigation treatments in a complete randomized block design were performed during 2014.This research was supported by the Spanish Ministerio de Economía y Competitividad (MINECO), (AGL2013-45922-C2-1-R).Peer Reviewe

Limitations and usefulness of maximum daily shrinkage (MDS) and trunk growth rate (TGR) indicators in the irrigation scheduling of table olive trees

8 páginas.-- 7 figuras.-- 2 tablas.-- 32 referenciasMaximum daily trunk shrinkage (MDS) is the most popular indicator derived from trunk diameter fluctuations in most fruit trees and has been reported to be one of the earliest signs in the detection of water stress. However, in some species such as olive trees (. Olea europaea L.), MDS does not usually change in water stress conditions and trunk growth rate (TGR) has been suggested as better indicator. Most of this lack of sensitivity to drought conditions has been related to the relationship between the MDS and the water potential. This curvilinear relationship produces an uncertain zone were great variations of water potential do not imply any changes of MDS. The MDS signal, the ratio between measured MDS and estimated MDS with full irrigation, has been thought to be a better indicator than MDS, as it reduces the effect of the environment. On the other hand, though literature results suggest an effect of environment in TGR values, there are not clear relationship between this indicator and meteorological data. The aims of this work are, on one hand, to study the improvements of the baseline approach in the MDS signal and, on the other, study the influence of several meteorological variables in TGR. Three years' data from an irrigation experiment were used in to carry out the MDS analysis and six years' data for full irrigated trees during pit hardening period were used for TGR study. The comparison between MDS vs. water potential and MDS signal vs. water potential presented a great scattering in both relationships. Values of MDS signal between 1.1 and 1.4 were always identified with moderate water stress conditions (-1.4 to -2. MPa of water potential). However, since this MDS signal values are around the maximum in the curvilineal relationship with water potential, greater values of MDS signal (in the range of 1.1-1.4) were not necessary lower values of water potential. In addition, during low fruit load seasons MDS signal was not an accurate indicator. On the other hand, absolute values of several climatological measurements were not significantly related with TGR. Only daily increments explain part of the variations of TGR in full irrigated trees. In all the data analysed, the daily increment of average vapour pressure deficit was the best indicator related with TGR. The increase of this indicator decreased TGR values. In addition, the agreement between this indicator and TGR was affected for fruit load. Great yield seasons decrease the influence of VPD increment in TGR.This research was supported by the Spanish Ministerio de Ciencia e Innovación (MICINN), (AGL2010-19201-CO4-03). Thanks are due to J. Rodriguez and A. Montero for help with field measurements.Peer reviewe

Assessment of discretely measured indicators and maximum daily trunk shrinkage for detecting water stress in pomegranate trees

Measurements obtained by the continuous monitoring of trunk diameter fluctuations were comparedwith discrete measurements of midday stem water potential and midday leaf conductance (gl)in adult pomegranate trees (Punica granatum L. cv. Mollar de Elche). Control plants (T0) were irrigateddaily above their crop water requirements in order to attain non-limiting soil water conditions in 2009 and 2010, while T1 plants were subjected to water stress by depriving them of irrigation water for34 days in 2010, after which time irrigation was restored and plant recovery was studied for 7 days.T1 plants showed a substantial degree of water stress, which developed slowly. Maximum daily trunkshrinkage (MDS) was identified to be the most suitable plant-based indicator for irrigation scheduling inadult pomegranate trees, because its signal:noise ((T1/T0):coefficient of variation) ratio was higher thanthat for midday stem water potential((T1/T0):coefficient of variation) and gl((T0/T1):coefficient of variation). MDS increasedin response to water stress, but when the stemfell below ¿1.67 MPa, the MDS values decreased. Fornon-limiting water conditions, MDS could be predicted from mean daily air temperature (Tm) throughexponential equations fitted to pooled data across several seasons. First-order equations were alsoobtained by pooling data across several seasons to predict MDS from crop reference evapotranspira-tion (ETo), mean daily air vapour pressure deficit (VPDm), Tmand solar radiation (Rs), but these should beused only within a certain range of values (ETo, 2.1¿7.4 mm; VPDm, 0.64¿2.96 kPa; Tm, 12.1¿28.3¿C; Rs,119.4¿331.3 Wm¿2). Hence, automated MDS measurements have the potential to be used in irrigationscheduling of pomegranate, and these values can be normalized to non-limiting water conditions bylocally derived empirical relationships with meteorological variables.Ministerio de Ciencia e Innovación (CICYT/FEDER) AGL2010-19201-C04-01AGRAgencia Española de Cooperación Internacional para el Desarrollo (AECID

Assessment of discretely measured indicators and maximum daily trunk shrinkage for detecting water stress in pomegranate trees

8 páginas.-- 7 figuras.-- 3 tablas.-- 50 referenciasMeasurements obtained by the continuous monitoring of trunk diameter fluctuations were comparedwith discrete measurements of midday stem water potential and midday leaf conductance (gl)in adult pomegranate trees (Punica granatum L. cv. Mollar de Elche). Control plants (T0) were irrigateddaily above their crop water requirements in order to attain non-limiting soil water conditions in 2009 and 2010, while T1 plants were subjected to water stress by depriving them of irrigation water for34 days in 2010, after which time irrigation was restored and plant recovery was studied for 7 days.T1 plants showed a substantial degree of water stress, which developed slowly. Maximum daily trunkshrinkage (MDS) was identified to be the most suitable plant-based indicator for irrigation scheduling inadult pomegranate trees, because its signal:noise ((T1/T0):coefficient of variation) ratio was higher thanthat for midday stem water potential((T1/T0):coefficient of variation) and gl((T0/T1):coefficient of variation). MDS increasedin response to water stress, but when the stemfell below ¿1.67 MPa, the MDS values decreased. Fornon-limiting water conditions, MDS could be predicted from mean daily air temperature (Tm) throughexponential equations fitted to pooled data across several seasons. First-order equations were alsoobtained by pooling data across several seasons to predict MDS from crop reference evapotranspira-tion (ETo), mean daily air vapour pressure deficit (VPDm), Tmand solar radiation (Rs), but these should beused only within a certain range of values (ETo, 2.1¿7.4 mm; VPDm, 0.64¿2.96 kPa; Tm, 12.1¿28.3¿C; Rs,119.4¿331.3 Wm¿2). Hence, automated MDS measurements have the potential to be used in irrigationscheduling of pomegranate, and these values can be normalized to non-limiting water conditions bylocally derived empirical relationships with meteorological variables.This research was supported by Ministerio de Ciencia e Innovación (MICINN) (CICYT/FEDER AGL2010-19201-C04-01AGR) and Agencia Española de Cooperación Internacional para el Desarrollo (AECID) (A1/035430/11) grants to the authors

Programación del riego deficitario controlado en aceituna de mesa empleando la dendrometría

La agricultura de riego es actualmente el mayor consumidor de agua en el mundo (Fereres y Evans 2006)). En muchas zonas áridas y semiáridas la escasez de recursos hídricos junto con la creciente demanda de agua para otros usos están imponiendo una fuerte presión para limitar su disponibilidad en la agricultura, un ejemplo muy claro es el caso de la agricultura Mediterránea. La optimización de este recurso natural se puede obtener a varios niveles pero posiblemente el menos estudiado y, con seguridad, el menos empleado a nivel comercial sea la programación del riego deficitario. Todavía es escasa la implantación de técnicas que realicen una toma de decisiones de riego de forma continua y telemática. El olivar, como cultivo tradicional y, muy recientemente, de regadío es un buen ejemplo