Unirrigated Trees Research Articles

Fertilization of Red Maple ( Acer rubrum) and Littleleaf Linden ( Tilia cordata) Trees at Recommended Rates Does Not Aid Tree Establishment

Landscape trees typically grow slowly for several years after transplanting. We investigated whether fertilization could speed tree growth during this establishment period, which fertilization regimes were most effective, and whether fertilization interacted with irrigation. Fifty-four each of landscape-sized, balled-and-burlapped red maple (Acer rubrum) and littleleaf linden (Tilia cordata) were planted into a relatively infertile silt loam soil and were fertilized (1.5 kg N/100 m 2[3 lb N/1000 ft 2]) each spring (either including or not including at planting), each fall, or not fertilized. Each of these fertilizer regimes was either irrigated or not irrigated during 3 years. An additional treatment of an unirrigated, split (spring/fall) fertilizer application was included. There was no evidence that fertilization affected irrigated trees differently than unirrigated trees. Overall, fertilization did not speed establishment and did not affect trunk growth, shoot extension, or leaf nitrogen content. There was no evidence that fall fertilization might be more effective than spring fertilization. There was no indication that fertilized trees experienced increased drought stress. Nitrogen rates and factors affecting fertilizer uptake are discussed.

Growth and development of fruits of olive ‘Frantoio’ under irrigated and rainfed conditions

SummaryA field experiment was performed in Tuscany, Italy, whereby fruit growth and development of irrigated olive trees (Olea europaea L. ‘Frantoio’) were compared, at two stages of fruit development, with those of trees cultivated under rainfed conditions. The fresh weight of fruits from irrigated trees was significantly higher than that from rainfed trees at 21 weeks after full bloom (AFB), whereas there were no differences at 8 weeks AFB or in fruit dry weight at both dates. Mesocarp transverse equatorial areas were 15.6 and 13.5% greater for the irrigated treatment than rainfed cultivated trees at 8 and 21 weeks AFB, respectively. Endocarp transverse area did not increase between 8 and 21 weeks AFB, indicating that endocarp expansion had occurred completely by 8 weeks AFB. The endocarp transverse area of irrigated trees was greater than that of unirrigated trees. For both treatments, mesocarp transverse area increased about 2.5-fold from 8 to 21 weeks AFB. Growth of the mesocarp between sampling dates was mainly due to a more than two-fold increase in mesocarp cell size for both treatments, whereas cell number increased only slightly over the same period. Irrigation appeared to increase mesocarp cell size rather than mesocarp cell number on both sampling dates. There were no differences in mesocarp oil content between irrigated and rainfed trees either at 8 or at 21 weeks AFB.

Interactions between root restriction, irrigation and rootstock treatments on ‘Queen Cox’ apple trees: Effects of soil and plant water relations

SummaryThe purpose of this research was to determine if established, orchard-grown apple trees that were con®ned in root-restricting membranes received adequate water for growth when irrigated. Previous data had shown positive effects of root restriction on reducing shoot extension growth in apple. Soil matric potential (Ψsm), leaf stomatal conductance (g) and leaf water potentials (Ψl) were measured over daily cycles during the period of maximum tree water use (July and August). Measurements were also made of the Ψsm and fruit size throughout the growing season. Daily and seasonal Ψsm showed that the soil within the root restricting membranes (+R) when irrigated (+I) remained closed to field capacity (<100 HPa), which was not the case for unirrigated soil within the membranes (-I +R). Ψl measured before dawn, showed that similar levels of drought stress were evident between irrigated and restricted (+I +R) and unrestricted (+I -R and -I -R) trees. The Ψsm, and Ψl for trees with roots within restricting membranes were significantly more negative, in the absence of irrigation (-I +R). Measurement of g showed that root restricted trees were transpiring at similar rates in the presence of irrigation (+I +R) as unrestricted trees (+I -R) with or without irrigation. Stomatal closure could not explain the increased Ψl observed for the restricted irrigated (+I +R) treatment compared with unrestricted (-R) trees. A reduced stomatal aperture was the most likely explanation for the reduction in growth previously observed with the restricted unirrigated trees. Fruit size was also affected by root restriction and the effect became greater as the roots became more restricted with tree age. Similarly, there was also a negative effect, in one year, of root restriction on fruit size at harvest, even in the presence of irrigation. Data show that reductions in soil water availability, Ψl and g, for the root-restricted trees (+I +R), were unlikely to be the causes for the previously observed reductions in shoot growth (tree size). These results imply that other factors were in operation, among which root-synthesized chemical regulators of shoot growth are the most likely candidates.

CARRY-OVER EFFECTS OF WATER AND NUTRIENT SUPPLY ON WATER USE OFPINUS TAEDA

A study of the effects of nutrients and water supply (2 × 2 factorial experiment) was conducted in a 12-yr-old stand of loblolly pine (Pinus taeda L.) during a period in which soil moisture was not augmented by irrigation because of frequent rain events. Information on the responses of sapwood-to-leaf area ratio and early-to-late wood ratio, to four years of treatments led to the hypothesis that the combination of increased nutrient and water supply (IF treatment) will increase tree transpiration rate per unit leaf area (EC,1) above EC,1 in the control (C), as well as increasing EC,1 above that when either the supply of water (I) or of nutrients (F) is increased. We further hypothesized that canopy transpiration (EC) will rank IF > F > I = C, based on the ranking of leaf area index (L) and assuming that the ranking of EC,1 is as first hypothesized. We rejected our first hypothesis, because F had lower EC,1 than the other treatments, rather than IF having higher values. We could not reject the second hypothesis; the ranking of average daily EC was 1.8 mm for IF, 1.2 mm for F, and 0.7 mm for both C and I (se < 0.1 mm for all treatments). Thus, it was the lower EC,1 of the F treatment, relative to IF, that resulted in ranking of EC similar to that hypothesized. Lower EC,1 in F trees was found to relate to lower canopy stomatal conductance, even though soil moisture conditions during the time of the study were similar in all treatments. Only trees in the F treatment absorbed a substantial amount of water (25%) below 1 m in the soil. These results indicate a “carry-over” effect of irrigation when combined with fertilization that increases EC in irrigated trees, relative to unirrigated trees, even under conditions when soil moisture is high and similar in all treatments.

Effects of soil water deficit on gas exchange characteristics and water relations of orchard lychee (Litchi chinensis Sonn.) trees.

Eight-year-old lychee (Litchi chinensis Sonn.) trees, cv. 'Bengal,' growing in krasnozem soil were subjected to soil water deficit from one month before flowering until harvest by covering the ground with polyethylene sheeting and withholding irrigation. The ratio of daytime stomatal conductance of unirrigated to irrigated trees decreased 20% during the three months of increasing water deficit. Predawn leaf water potentials of irrigated trees averaged about -0.3 MPa throughout the period, whereas they declined progressively to -0.9 MPa in unirrigated trees. Minimum daytime leaf water potential in the unirrigated trees decreased from -1.0 to -1.1 MPa at the beginning of the drought period to -2.2 to -2.4 MPa after three months, and calculated whole-plant conductance did not change with decreasing availability of water. The calculated soil-root water potential declined to less than -1.0 MPa in unirrigated trees. Capacitance effects on the relationship between leaf water potential and transpiration were significant only at low transpiration rates. Although unirrigated trees reduced soil water content at 0-30 cm depths to an equivalent water potential of -1.0 MPa, fruit shedding was significantly less than in irrigated trees. Water deficit had no effect on the fresh weight of pericarp, but caused increased seed size and decreased fresh weight of flesh, resulting in fruit from unirrigated trees being 16% lower in total fresh weight per fruit than fruit from irrigated trees.

Shoot growth-flowering relationships in the sour cherry ‘Stevnsbaer’ as affected by water and nutrient supply

SummaryExtension growth and flower bud formation were studied in unirrigated and drip irrigated field-grown one year old ‘Stevnbaer’ sour cherry trees as well as in drip irrigated pot- grown trees. Fertigation in the field increased shoot length and number of shoots as compared with unirrigated trees, but decreased the number of flower buds. Fertigated trees in pots with ample water and nutrient supply exhibited vigorous shoot growth with many shoots longer than 45 cm, and developed more flowers and a higher blossom density. Still, within pot-grown trees, blossom densities decreased with increasing shoot length. On short shoots, the number of flowers per truss on pot-grown trees may have exceeded those on field-grown trees. On longer shoots, flower buds were situated in the upper part of the shoot. The relationships between extension growth and flower bud formation as affected by nutrition are discussed.

Stem-water Potential as a Sensitive Indicator of Water Stress in Prune Trees (Prunus domestica L. cv. French)

The relative sensitivity of plant- and soil-based measures of water availability were compared for prune trees subjected to a range of irrigation regimes under field conditions. Over the growing season, leaf- and stem-water potentials (ψ) measured at midday exhibited clear differences between frequently irrigated trees and unirrigated trees that were growing on stored soil moisture. Stem ψ was less variable than leaf ψ, and the daily variability in stem ψ was closely related to daily variability in evaporative demands, as measured by vapor pressure deficit (VPD). As a result of lower variability, stem ψ reflected the small stress effect of a moderate, 50% soil moisture depletion irrigation interval, whereas leaf ψ did not. The relation between soil water content and estimated orchard evapotranspiration (ET) was influenced by local differences in soil texture within the experimental plot. The relation between stem ψ and ET, however, was not influenced by soil texture and, in addition, was very similar to the relation between stem ψ and leaf stomatal conductance. Both relationships indicated that a 50% reduction in leaf and canopy level water loss characteristics was associated with relatively small reductions (0.5 to 0.6 MPa) in stem ψ. Stem ψ appears to be a sensitive and reliable plant-based measure of water stress in prune and maybe a useful tool for experimental work and irrigation scheduling.

Fertigation of newly planted ‘Queen Cox’/M.9 apple trees: Establishment, early growth and precocity of cropping

The effects of a compound soluble 19:6:6 fertilizer applied in trickle irrigation (fertigation) at rates between 10 and 80 g N per tree per year were compared with irrigation alone, broadcast fertilizer at 80 g N per tree per year and no fertilizer or irrigation on trees planted in 1987. Trees receiving irrigation had shoot growth similar to the unirrigated trees either with or without broadcast fertilizer except in 1990 when irrigation substantially increased shoot growth compared with the other two treatments. Trees receiving fertigation at 10 and 20 g N per tree had similar total shoot lengths to those receiving irrigation but fruit set on spur and terminal flower clusters was increased and this was reflected in an increased cumulative yield of apples from 1988-90. Compared with all other treatments, fertigation at 40 and 80 g N per tree caused large increases in total shoot growth associated with an excessive production of axillary floral buds that abscinded leaving unproductive bare wood. Yield of ap...

Cellular basis for limitation of poplar leaf growth by water deficit.

During the summers of 1986 and 1987, stem and leaf growth were measured on coppiced plants of Populus trichocarpa Torr. & A. Gray, P. deltoides Bartr. ex Marsh, and P. trichocarpa x deltoides growing in the field in Puyallup, WA. The trees were either irrigated periodically throughout the season, or grown without irrigation. In both treatments, stem volume at the end of the growing season was directly proportional to total leaf area in all three genotypes. The rate of individual leaf growth was reduced by lack of irrigation more in the parental species than in the hybrid. Only in the parental species did unirrigated trees have lower leaf water potentials (predawn and midday) than irrigated trees. However, stomatal conductances of all three genotypes were lower in unirrigated trees than in irrigated trees. Osmotic potentials of growing leaves of all three genotypes were also lower in unirrigated trees than in irrigated trees. As a consequence, turgor of growing leaves was as great in unirrigated trees as in irrigated trees, which indicates that turgor differences cannot explain the lower rates of leaf growth in the unirrigated trees. However, cell wall extensibility of leaves was lower in unirrigated trees than in irrigated trees, and the difference was greater in the parental species than in the hybrid. Unlike its effect on leaf area growth, irrigation increased stem volume growth of the hybrid and the parental species by a similar amount (12-16%).

Microsprinkler Irrigation and Microclimate of Young Orange Trees During Freeze Conditions

Abstract Two-year-old ‘Hamlin’ orange trees [Citrus sinensis (L.) Osb.],on Poncirus trifoliata (L.) Raf. rootstock were used to study the effects of various microsprinkler irrigation rates and spray patterns on trunk temperatures and microclimate during freeze conditions. Irrigation treatments consisted of a factorial combination of two spray patterns (90° and 360°) × three application rates (38, 57, and 87 liters hr−1), plus an unirrigated control. All trunks were wrapped with fiberglass insulation. Trunk temperatures were 1° to 5°C higher for irrigated than unirrigated trees, regardless of spray pattern or application rate and were 1° to 2°C higher with the 90° than 360° spray pattern. The 57 and 87 liter·hr−1 rates produced the highest trunk temperatures, although 38 liter·hr−1 maintained trunk temperatures above −2.5°C with air temperatures as low as − 12°C. Outgoing radiation was higher for irrigated than unirrigated treatments during advective freeze conditions only, but air temperature and vapor pressure were unaffected by microsprinker irrigation.

Responses of Young Almond Trees to Two Drought Periods in the Field

SummaryWater potential, conductance to water vapour diffusion and 14CO2 uptake rate were measured in the field on leaves of young, trickle-irrigated almond trees subjected to drought periods. Treatments imposed were: T. two one-month drying cycles with an interim period of recovery; T2, a single one-month drying cycle; T3, a single 2.5-month drying cycle; and T4, daily irrigation. Midday leaf water potential in T, and T2 trees decreased 0.8 to 1.0 MPa below that of the control, and that of T3 trees was further decreased by about 0.7 MPa. Turgor pressure was partially maintained in the stressed treatments through osmotic adjustment. Osmotic potential at full turgor in leaves of unirrigated trees was about 0.3 MPa lower than in the controls and was the same at the end of both drought cycles. Decreases in osmotic potential were accompanied by increases in dry weight per unit leaf area. Despite partial maintenance of turgor, water stress decreased leaf conductance and 14CO2 uptake. Leaf conductance and 14CO2 uptake correlated well over a wide range of water-stress conditions. Stomatal closure during both drying periods occurred gradually over a wide range of decreasing leaf water potential. Water stress resulted in leaf rolling and shedding. Both effects caused the solar radiation intercepted by the trees to decrease by the end of the second drought period from 80% in the control trees to less than 50% for trees that had leaf water potential below —3.0 Mpa.

Photosynthesis and Transpiration of Pinus Radiata D. Don Under Plantation Conditions in Southern Australia. I. Response to Irrigation With Waste Water.

A plantation of P. radiata growing on sandy soil responded by greatly increased growth to applications of waste water over 3 years. Foliar concentrations of phosphorus and potassium increased following imgation but, although the waste water contained sodium up to 200 mg l-�, the concentration of sodium in the foliage remained low. Maximum rates of photosynthesis of branches within the canopy were 1 .8 �mol m-� s-� (imgated trees) and 0.7 �mol m-� s-� (unimgated trees). Needle conductance (g,) in imgated trees was 20-50 mmol m-� s-� and, in unimgated trees, less than 10 mmol m-2 s-�. Greater rates of photosynthesis in imgated trees might be explained by greater values of g*l; variations in the rate of photosynthesis during the course of a day did not, however, always follow variations in g*l particularly in irrigated trees. Needle water potential (�*p) of imgated trees reached a minimum of -2.0 MPa during the day, indicating a large internal resistance to the transport of water through the tree. Minimum �*p of unirrigated trees was -2.6 MPa; substantial rainfall during the measurement period did not reduce the difference in �*p between imgated and unimgated trees.

Nitrogen and Water Effects on the Nutrition, Growth, Crop Yield and Fruit Quality of Orchard-Grown Cox’s Orange Pippin Apple Trees

SummaryNitrogen was applied at 26, 78, 130 or 182 kg N ha-1 as a single annual dressing either in October or March to Cox’s Orange Pippin apple trees on MM. 104 rootstock that were irrigated early (June only), late (July to mid-September), early + late, or left unirrigated. Treatments continued for nine years. The lowest rate of N did not maintain a non-limiting N status in the trees indicated by a leaf level of 2.4% of dry matter. All the higher rates did so, and, compared with minimum N, increased growth, initial set and fruit numbers at harvest but decreased fruit size. Irrigation increased growth and cropping, but its effect on growth was greatest when rainfall was well below average (June-August) and when cropping of mature trees was heavy. Early irrigation increased fruit numbers at harvest and decreased fruit size compared with no irrigation. Late irrigation had no effect on fruit number but had a very marked effect on size and quality, increasing the two highest quality grades by 67% over unirrigated trees during 1971–5 when 80% of the cumulative crop yield was produced. Maximum crops of high quality were obtained by the combination of adequate N (78 kg N ha-1) to ensure fruit set, and late irrigation to ensure good size and quality. Early + late irrigation was less effective. Increasing N reduced the incidence of bitter pit, but irrigation reduced it only in fruit from trees that had received the lower N rates. There were no growth or cropping effects due to the time of N application.

Shoot growth inCoffea arabicaL. I. Responses to rainfall when the soil moisture status and gibberellin supply are not limiting

SummaryIndividual branches on mature trees of Coffea arabica L. growing in the field at Ruiru, Kenya, which were treated weekly with saturating doses of gibberellin and beneath which the soil was irrigated weekly to keep it near to field capacity, produced leaves faster when it rained and the temperature fell rapidly during the day. Unirrigated trees behaved differently, irrespective of gibberellin treatments, failing to ‘flush’ on two occasions and responding more than the irrigated trees to the main rains in May. The trees appeared more sensitive to gibberellin during the hot, dry season than during the rainy season or the cool, dry season. Both . irrigation and gibberellin, which failed to replace the effect of irrigation, increased internode extension proportionately more than node production.

The effect of irrigation on the growth, cropping and nutrition of Cox’s Orange Pippin apple trees

SummaryCox’s Orange Pippin apple trees on M.II rootstock growing in grass on a coarse sandy loam of medium moisture retention were used to study growth and crop responses to irrigation from 1958 to 1966 inclusive. Treatments A, B and C consisted of 1, 2 and 3 in† of water applied at calculated soil moisture deficits of 1, 3 and 5 in respectively. The trees in Treatment D were not irrigated.Soil moisture deficits calculated from potential evaporation over-estimated measured soil moisture deficits by as much as 20%.Shoot and trunk growth were stimulated by irrigation during the first four years, but when the trees began to bear heavy crops the effects of watering on growth diminished considerably.Heavy bearing was not delayed by the vigorous growth induced by irrigation, and at full bearing crop yields were commensurate with the growth made. In three successive years of high yields the trees under Treatments A, B and C yielded 42%, 37% and 25% more respectively than the unwatered trees.Treatment A was uneconomical compared with B, and the latter afforded better cropping potentialities than Treatment C. There was no consistently positive effect of irrigation on fruit size, but a larger crop was generally carried on the irrigated trees without loss of size compared with the unwatered trees.In the eighth and ninth years of the experiment there was an abrupt depression in yield which was strongly associated with a depression in leaf Ca and Mg levels and an increase in the level of leaf K. Irrigated trees were more seriously affected than unirrigated trees. A nutritional effect of irrigation on the level of cropping was indicated but not established.

Effect of Irrigation on Autumn Leaf Coloration in the Purpleblow Maple, Acer Truncatum Bunge1

Abstract Acer truncatum trees, 8-11 years old were irrigated three times during the summer, and autumn leaf coloration was compared with unirrigated trees. The irrigated trees colored significantly better, and the coloring period occurred 4-5 days later than the unirrigated trees. Irrigation had no effect on the length of the period of coloration or on the average color of the leaves.