Amount Of Supplemental Irrigation Research Articles

Effect of Time and Amount of Supplemental Irrigation at Different Distances from Tree Trunks on Quantity and Quality of Rain-fed Fig Production

Supplemental irrigation under prolonged drought conditions has a key role in providing water for transpiration of rain-fed fig trees. The effect of different times and amounts of supplemental irrigation at different distances from the tree trunk on quantity and quality of Estahban rain-fed fig production was evaluated during two years. A randomized complete block design with four replications on fig cultivars of Sabz was used to conduct the experiment. Treatments of supplemental irrigation included three different application positions including: close to tree trunks (NT); 1-1.1 m from tree trunk (UT) and outside of tree canopy (OT), using three different quantities of irrigation water as no supplemental irrigation (control), 1000 and 2000 liters irrigation water per tree, and with two different supplemental irrigation times in early spring and mid-summer. Results showed higher soil water content for irrigation during early spring, near tree trunk with 2000 liters irrigation water per tree. Despite the reduction in total soluble solids (TSS), supplemental irrigation improved the yield, size and skin color of fruits compared to the control. In both years, fig yield was higher in NT and OT treatments compared to UT. Irrigation out of canopy produced more fruits with higher quality. A non-significant difference between yields in irrigation water amount treatments during the second year indicated the adequacy of 1000 liters per tree. Application of 1000 liters, out of canopy in mid-summer would be recommended to fulfill marketing goals and sustainable use of regional water resource under drought conditions in rain-fed fig orchards.

Time and amount of supplemental irrigation at different distances from tree trunks influence on morphological characteristics and physiological responses of rainfed fig trees under drought conditions

This study was carried out to identify the effects of time and amount of supplemental irrigation (SI) at different distances from tree trunks on morphological characteristics and physiological responses of mature rainfed fig trees in Estahban County, Fars Province, Iran. The two-year experiment was conducted in a split-split plot statistical design with four replications. SI treatments consisted of 1) irrigation position treatments in a micro-catchment close to tree trunks, 1–1.1 m from tree trunks inside of canopy, and 2.1–2.2 m from tree trunks outside of canopy 2) irrigation time treatments in early spring and in mid-summer, and 3) irrigation water amount treatments of no supplemental irrigation (control), 1000 liters, and 2000 liters of irrigation water per tree. The results showed a positive effect of SI on some morphological traits of rainfed fig trees. SI increased the leaf gas exchange parameters, including net photosynthesis rate (An), transpiration rate (Tr), and stomatal conductance (gs). The highest An and gs occurred in leaf water potential (LWP) around -1 MPa and the air temperature of 20 °C. The LWP equal to −2 MPa could be considered as a threshold for stomatal closure of rainfed fig trees, which put this plant among drought-tolerant trees. The higher correlation coefficient between An and gs compared with that obtained for An and Tr implied the higher dependence of the An variation on the gs than that of Tr. The highest leaf scale water use efficiency for trees irrigated with 2000 liters of water, out of the canopy, indicated higher increase of An compared with Tr after irrigation. Applying SI with 2000 liters of water per tree (200 m3 ha−1), outside of canopy in early spring could improve some of the morphological traits and physiological responses of rainfed fig trees, under drought conditions. However, under water resources limitation, 1000 liters of irrigation water per tree (100 m3 ha−1) could be recommended for rainfed fig orchards.

Time and amount of supplemental irrigation at different distances from tree trunks influence on soil water distribution, evaporation and evapotranspiration in rainfed fig orchards

This study was carried out in Estahban, Iran, during 2013 and 2014 to identify the optimal time and amount of supplemental irrigation at different distances from tree trunks on a rainfed fig orchard. This region is distinguished as the largest producer of dried figs in Iran and the world and its production is highly dependent on precipitation. A split–split plot statistical design with four replicates was used to conduct the experiment. Irrigation treatments based on the position of application around trees were: in a micro-catchment close to tree trunks; in three holes inside of tree canopies with a mean canopy of 3.2 m diameter (placed 1–1.1 m from tree trunks); and in four holes outside of tree canopies placed 2.1–2.2 m from tree trunks were used in this experiment. Irrigation time treatments consisted of: (a) in early spring; (b) in mid-summer and the three different volumes of irrigation water were used: no supplemental irrigation (control), and either 1000 or 2000 l of irrigation water per tree. Results showed a high evaporation rate in the area which used nearly half of the rainfall during autumn and winter. There was a significant positive correlation between soil water content (SWC) and temporal rainfall distribution as r** = 0.63 (p < 0.001) over two years. Under drought conditions, irrigated trees showed higher ETa that was close to the ETa in years with normal rainfall. Compared to irrigation in summer, irrigation in early spring kept higher SWC for a longer time period in the soil profile and irrigation far from trees increased soil surface evaporation especially in summer. This study suggests that using supplemental irrigation with 2000 l per tree of water in early spring near tree trunk could provide higher SWC and lower surface evaporation for rainfed fig orchards during drought conditions.