Search Results
A time domain reflectometry (TDR) technique was used to measure water in the soil profile to derive wetting patterns of drip and microjet irrigation systems in a peach [Prunus persica (L.) Batsch] orchard. A distinct cone shape of >50% available soil water (ASW) extending from the emitter down to a depth of >45 cm was observed in the drip system. The 50% ASW zone in the microjet system was an elongated semicircle from the soil's surface down to a depth of 35 cm. TDR can be used successfully to determine wetting patterns of various irrigation systems to develop better irrigation scheduling.
Abstract
Germination of tomato (Lycopersicon esculentum Mill.) seeds in petri dishes at various levels of water stress was comparable, except under conditions of severe stress when a PEG pretreatment improved final percentage germination and enhanced the onset and rate of germination. At intermediate or high watering levels, PEG-pretreated seeds germinated more rapidly than untreated seeds, but final germination was not altered by PEG. Germination of seeds in soil, under controlled laboratory conditions, was similar to that in petri dishes except under the driest conditions (5% ASM) when little emergence occurred whether the seeds were pretreated or not. A majority of the seeds which failed to germinate after 2 weeks under dry soil conditions were still viable, since subsequently they could be induced to germinate by moistening the soil to 100% ASM. Water requirement of tomato seeds for optimal rate of germination was cultivar dependent; PI-341988 seeds germinated well at 60% ASM or greater, whereas ST-24 required 100% ASM for best germination.
Abstract
The effects of irrigation and tree density on peach [Prunus persica (L.) Batsch cv. Harken/Siberian C] production were investigated over 11 years. Irrigation improved growth of peach trees, lowered levels of winter injury and perennial canker (Leucostoma spp.), and promoted tree survival. Annual and cumulative marketable yields were increased, especially in the later years. Tree density did not affect perennial canker, winter injury, or tree survival. Reducing tree spacing increased resulted total growth per hectare and annual and cumulative marketable yields. Irrigation and density treatments usually did not interact and had an additive effect on growth and fruit production. The most productive management system (a combination of 50% available soil moisture and 536 trees/ha) resulted in accumulated yields over 8 years of 179 tonnes (t)/ha comparted with only 74 t/ha for the check treatment (no irrigation and 266 trees/ha).
Abstract
Root systems were studied to determine if differences in utilization of soil moisture were associated with the extent and number of roots produced by corn and tomato. Growth room studies for both crops indicated that the reduction in transpiration when the upper portion of the root zone was dry was greater than when the lower portion was dry. Total root length of corn was about twice that of tomato roots. However, no direct relationship between the total amount of root length and transpiration was found. Roots of corn and tomato in the field extended beyond the maximum depth measured (100 cm) between 42 – 46 days after establishment. The spatial density of corn roots was much greater than that of tomato roots, especially as depths increased. This difference possibly explains the use of stored soil moisture by corn. On the other hand, the capacity of tomatoes to extract large amounts of water from the soil cannot be explained by the density and rooting depth. Perhaps this capacity is due to total root surface area differences or high absorption capacity of tomato root system.
Abstract
Peach [Prunus persica (L.) Batsch] seedlings were grown in large sectional boxes with root systems divided into 4 separate quadrants. Groups of peach seedlings with 3, 2, 1, and 0 quadrants of the root system deprived of water for 3 weeks, were further subjected to moisture stress in all quadrants by withholding water for 5 days, and they were then rewatered. In another treatment, seedlings were subjected to 2 cycles of water stress, applied 3 weeks apart, by completely depriving all quadrants of water until the plants wilted. Transpiration, photosynthesis, stomatal conductance, and xylem pressure potential were measured. Subjecting a large portion of the root (50%) to stress by withholding water only caused a small reduction (17%) in transpiration, photosynthesis, and stomatal conductance. Subjection of various fractions of the root system to severe moisture stress did not affect the shoot:root ratio. The reduction in root growth in dry quadrants was accompanied by the production of more roots in wet quadrants and less transpiring leaf surface and branch growth. The rate of recovery of transpiration and photosynthesis from water stress was greatly influenced by the duration and intensity of wilting as well as by the rate of regeneration of new root systems.
Abstract
Three-year-old peach [Prunus persica (L.) Batsch] trees in a growth room under well-watered conditions were subjected to photosynthetically active radiation (PAR) levels (400-700 nm) of 444, 287, 144, 61, and 19 μmol°s−1m−2. At very low PAR levels (19 and 61 μmol°s−1m−2), the photosynthetic rate (P) declined with increasing temperature. Multiple regression analyses for the 3 highest PAR levels showed that an increase in PAR increased the optimum temperature for both P and stomatal conductance (gs). The highest leaf water potential (ψL) was found at 21°C in all 3 PAR levels. The regression equations also showed that PAR was the main determinant of P and gs, but that temperature was the main determinant of ψL.
Abstract
Three cultivars (early, midseason, late), two ground covers (clean cultivation followed by temporary cover vs. permanent sod strips), and trickle vs. no irrigation were studied in a high-density (633 trees/ha) experimental peach orchard established in 1980 on Fox sand. Growth rate in the first 5 years was similar for all three cultivars. It was retarded up to 12% by permanent sod relative to temporary cover and enhanced up to 30% by trickle irrigation vs. no irrigation. Total marketable yields and that of large-sized fruit (>6.3 cm) were significantly influenced by cultivars in the first and second, but not the third year of production. Ground cover treatments did not influence total marketable yields, but did affect the yield of large fruit in one year. Irrigation increased total marketable yields each year and also increased the yield of large fruit. Yields were up to 30.7% higher in trickle vs. non-irrigated plots. Cold hardiness of flower buds and shoot xylem in 1982 was significantly influenced by cultivar and irrigation treatments, but not by ground cover treatments; In 1984, each of these factors affected cold hardiness. Foliation in 1984 was affected by ground cover and irrigation treatments but not by cultivars. The best treatment combination across cultivars for management of the orchard floor consisted of permanent sod strips of creeping red fescue (Festuca rubra L.) in the row middles combined with trickle irrigation in the tree row.
Abstract
Stomatal conductance, transpiration, and photosynthesis declined steadily with decreasing leaf water potential in seedlings of peach [Prunus persica (L.) Batsch] grown in large pots containing about 84 kg of steam-sterilized sandy loam soil under controlled environmental conditions. Growth and transpiration were reduced mainly through the effect of stomatal closure as soon as water stress commenced.
Abstract
The trench profile method was used to map peach [Prunus persica (L.) Batsch cv. Harken/Siberian C] roots in an 11-year-old experimental orchard with 3 levels of irrigation and 3 tree densities. Roots near the drip line, 150 cm from the trunk, were mapped to a depth of 120 cm, while those 30 cm from the trunk were mapped to a depth of 240 cm. Location, number, and diameter of roots near the drip line were greatly affected by irrigation and only moderately affected by tree density. The total number, and number of small-diameter (<2 mm) roots were highest in nonirrigated plots and decreased with increasing levels of irrigation. A similar but much reduced pattern was evident for medium- (2 to 5 mm) and large- (>5 mm) diameter roots. Irrigation promoted shallow rooting near the drip line. Trees receiving the low and high level of irrigation had 35% and 42%, respectively, of their roots in the top 30 cm of soil, compared with only 18% for those in nonirrigated plots. At depths of 30 to 120 cm in nonirrigated plots, 82% of the roots near the drip line were found in these soil layers, compared with 65% for the low and 58% for the high level of irrigation. Tree density had no effect on total root number near the drip line, although there was an increase in root number with an increase in tree density 90 to 120 cm from the trunk on both sides of the tree, and a decrease in root number with an increase in tree density within 60 cm of the trunk. Rooting occurred readily in the Ap, Bm, and Bt soil horizons, but very little rooting occurred in the gray sand comprising the Ck horizon, which had a high pH (7.8) and poor soil water retention characteristics.
Abstract
A 2-year study was made of 2 methods of scheduling irrigation of peach (Prunus persica (L.) Batsch cv. Harken/Siberian C). In each year, irrigation schedules necessary to prevent the available soil moisture (ASM) from falling below 50% level in the top 30 cm were essentially the same, whether determined from direct measurement of soil moisture or predicted from a simplified Priestley and Taylor évapotranspiration model.