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In South Texas, most of tomato (Lycopersicon esculentum Mill.) crops are produced on plastic mulch due to the elevated temperatures and solar radiations. The study objectives were to; Determine the suitable planting dates for increasing tomato varieties production under different planting dates in early spring and late winter, and evaluate the influence of using the plastic mulch (black and white. In the Spring season, nine tomato varieties (four rounds and five roma) were grown. The round varieties were the Torero, Mykonos, Shourouq, and TAM Hot-Ty, and the roma varieties were Prunus, Rio Grande, Seri, DRP-8551, and SV8579TE. The best five varieties from the spring season and two more varieties were selected for evaluation in the fall including; SV8579ET, Mykonos, DRP-8551, TAM-HOT-T4, Shourouq, Tycoon, and Everglade. All the tomato varieties were evaluated during the Spring season under three different planting dates (from late-February till late-March) and three mulching treatments (black, white plastic mulch, and bare soil); and during the fall season during two planting dates (from early to midSeptember) and two mulching treatments (black and white plastic mulch). Higher average marketable yields were observed in the spring season than the fall season. The best varieties during the spring season were DRP-8551, SV8597TE, Shourouq, and Seri with yields ranging from 68,630 to 57,237 kg/ha, whereas the best varieties in the fall; were DRP-8551, SV8597TE, and Tycoon with yields ranging from 47,123 to 60,674 kg/ha. In both seasons, white plastic mulch resulted in higher yields compared to the black and bare tomato yields.

This experiment evaluates the potential of using parameters based on tree trunk fluctuations for detecting water deficit in citrus trees under two different water saving-irrigation strategies: sustained deficit irrigation and partial root-zone drying. Three irrigation treatments were applied: 1) Control: trees were irrigated with 100% of their evapotranspirative needs (ETc); 2) 60 sustained deficit irrigation (SDI): 60% ETc; and 3) partial root-zone drying (PRD): 100% ETc needs, applied to only one-half of root zone. Maximum daily shrinkage (MDS), trunk growth rate (TGR), and MDS ratio (ratio between MDS of stressed trees and control trees) were determined. Day-to-day MDS values varied largely and could not be used to determine tree water deficit. TGR did not show significant differences among treatments at this level of stress. Nevertheless, the MDS ratio was a reliable indicator to measure tree water status, and it was more sensitive for detecting water deficit at the onset of a water deficit in trees under SDI than in trees under PRD.Additional key words: dendrometer, maximum daily shrinkage, partial root-zone drying, stem water potential, sustained deficit irrigation, trunk diameter Hort. Environ. Biotechnol. 56(3):305-309. 2015.

Regulated deficit irrigation (RDI), recommended for super-high density (SHD) olive orchards, requires a precise control of irrigation. Water must be supplied on the phenological stages when the plant is most sensitive to water stress,

The aim of this work was to evaluate the potential of used sap flow (SF), trunk diameter variation (TDV) and leaf turgor (LT) sensors for assessing water stress in a 'Arbequina' hedgerow olive orchard with 1667 trees ha -1 . Measurements were made in control trees irrigated to replace 100% of the crop water needs, and in trees under two regulated deficit irrigation strategies, 60RDI and 30RDI, in which irrigation replaced ca. 60% and 30% of the control, respectively. From the SF and TDV measurements we calculated the daily difference, both for tree water consumption (D Ep ) and maximum trunk diameter (D MXTD ), between RDI trees and control trees. With the LT sensors we recorded the leaf patch output pressure (P p ), which is related to the leaf turgor pressure. Both D Ep and D MXTD responded quickly and markedly to changes in water stress. The seasonal dynamics of both indices agreed with that of the stem water potential. A decrease in the reliability of D Ep was recorded on days of highly variable atmospheric demand. The LT sensors also showed to be highly sensitive to changes on water stress. Any of the three methods have a potential as indicators for precise irrigation in hedgerow olive orchards with high plant density and low soil water-holding capacity.

Sugarcane production can be affected by extreme environmental conditions, such as drought stress. This study focused on establishing a screening method to evaluate and select drought tolerant germplasm of Saccharum species. A new drought screening methodology is presented in this paper. A randomized block design experiment was conducted under greenhouse conditions with 2 months old seedlings of five genotypes of Saccharum spontaneum (IRAN 28, JW43, TUS12-72, TUS12-23, X08-0299) and one genotype of a commercial cultivar (Saccharum spp. CP72-1210), under well-irrigated and water stress conditions. Three treatments were established with irrigation intervals at 3, 6, and 9 days, with four replicates per each genotype in each treatment. Evapotranspiration, stomatal conductance, total biomass, leaf death rate, rate of new tillers and shoot growth were evaluated during the experiment. JW43 and CP72-1210 presented the highest values of stomatal conductance with non-significant differences. Accumulated water used by all the genotypes was significantly different among the three treatments. Also, significant differences were found in the total dry biomass among all the treatments. Results showed that TUS12-23 genotype can be classified as very tolerant to drought stress and JW43 is the less tolerant, whereas the other genotypes could be susceptible and may survive under mild drought conditions. Results also indicated that the methodology used, and the parameters measured are effective in identifying sugarcane germplasm with extreme reaction to drought stress.