Heavy Crop Year Research Articles

Long-terms effects of irrigation with treated municipal wastewater on soil, yield and olive oil quality

In Tunisia, water scarcity is one of the major constraints for agricultural activities. The reuse of treated wastewater (TWW) in agriculture can be a sustainable solution to face water scarcity. The research was conducted for a period of ten years in an olive orchard planted on a sandy–silty soil and subjected to two different irrigation treatments: (a) well water (WW) and (b) treated wastewater (TWW). The main aim of the present study was to investigate the influence of irrigation with TWW on soil chemical properties, olive tree yield and on virgin olive oil (VOO) quality during an heavy crop year (“on year”) in “Chemlali” olive orchard. Soil samples were collected at the beginning of the study (before irrigation), after five and ten years for each treatment. pH, electrical conductivity (EC), organic matter, major elements, salts and heavy metals contents in soil were investigated. Standard quality parameters, chlorophyll, β-carotene, total phenols (TP), induction time and total tocopherols such as α-,β-,γ-,δ-tocopherol of VOOs were also investigated. Results showed that irrigation with TWW increased soil pH, EC, OM, major elements, salts and heavy metals contents. Data obtained indicated that standard quality indices (free acidity, K232, and K270) of VOO and oil content were not affected significantly by water quality. Instead, chlorophyll, total phenols, induction time and δ-tocopherol values decreased significantly after ten years of irrigation with TWW. However, both fruit water content, and the concentrations of β-carotene and tocopherols (α, β and γ) in VOO increased.

Long-term individual-level variation of reproductive features in Sorbus aucuparia, a fleshy-fruited tree

Synchrony and fluctuation in reproductive output was not associated in individual trees. In a study conducted at the central Cantabrian Range, northern Iberia, we analyzed the fruiting pattern of 54 rowans (Sorbus aucuparia), a fleshy-fruited tree, over 16 consecutive years. Our objectives were: (a) to assess the covariation between several variables related to the reproductive performance of individual trees; (b) to measure the degree of synchrony shown by individuals; and (c) to address whether the reproductive behavior of individuals changed over the period of study. The fruiting performance of individuals was assessed in terms of the individual coefficient of variation in fruit output (CV i ), synchrony (as the correlation between fruiting patterns), and the frequency of heavy crop years. Mean synchrony (0.52 ± 0.18) and CV i values were large (1.92 ± 0.33) and correlated negatively. The average tree was synchronized with 60 ± 22 % of its conspecifics and about 36 ± 14 % of its fruiting years were heavy crop years. The study population included a distinct and small set of asynchronous trees and the synchrony between individual fruiting patterns was markedly reduced during the second half of the study period.

Does a heavy fruit crop reduce the tree ring increment? Results from a 12-year study in a subalpine zone

Life history theory posits that an increased investment in reproduction should result in decreased vegetative investment. Switching resources from growth to reproduction are also expected in species experiencing selection pressure for high variation of seed crops. In this study, we tested whether the reproductive effort of trees, measured as the number of fruits produced, is related to their radial growth increment. We examined a population of Sorbus aucuparia, a fleshy-fruited tree species with highly variable interannual individual fruit production growing in the subalpine zone and under strong selection pressure from pre-dispersal seed predators. We used 12-year data to test the relationship between fruit crop and radial growth increments in current, previous and subsequent years, and found no trade-off between growth and reproduction. For almost all trees, there was no correlation between fruit crop and radial growth increment in the same year or next year. Only a few trees showed a positive correlation between fruit crop and previous-year growth. In the statistics, we took advantage of the high variability of individual fruit crops in high production years. In four heavy crop years, we compared the radial growth increments of trees with heavy crops with those of trees with low fruit crops. Current and next-year radial growth did not differ between trees with low and high fruit crops. In all those years, however, trees having heavy fruit crops had higher previous-year growth increments. We suggest that the harsh subalpine weather conditions account for the lack of a trade-off between growth and reproduction in the studied population.

Population and individual level of masting in a fleshy-fruited tree

Masting is usually considered as a population phenomenon but it results from individuals’ reproductive patterns. Studies of individual patterns of seed production and their synchrony are essential to an understanding of the mechanisms of masting. The aim of this study was to find the relationship between population and individual levels of masting. We examined individuals’ contribution to masting, considering their endogenous cycles, interannual variability and associated weather cues, as well as inter-individual synchrony of fruit production. We studied masting of Sorbus aucuparia L., which in Europe is one of the most common trees bearing fleshy fruits and is strongly affected by a specialized seed predator. The data are 11-year measurements of fruit production of 250 individuals distributed on a 27-ha area of subalpine forest in the Western Carpathians (Poland). Population- and individual-level interannual variability of fruit production was moderate. Synchrony among individuals was relatively high for all years, but the trees were much less synchronized in heavy crop years than in years of low fruit production. Weak synchrony among trees for heavy production years suggests that the predator satiation hypothesis does not explain the observed masting behavior. Fruit production, both at individual and at population level, was highly correlated with weather conditions. However, the presence of masting cannot be fully explained by the resource-matching hypothesis either. We suggest that adverse weather conditions effectively limit fruit production, causing high inter-individual synchrony in low crop years, whereas the unsynchronized heavy crop years seem to have been affected by individually available resources.

Nitrogen Fertigation Concentration and Timing of Application Affect Nitrogen Nutrition, Yield, Firmness, and Color of Apples Grown at High Density

A randomized complete block, split-plot experiment with six replicates was established and maintained for the first six fruiting seasons (1999 to 2004) in a high-density apple [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] orchard on M.9 rootstock planted in Apr. 1998. This report assesses responses to six main-plot fertigation treatments, each containing three tree subplots of five different cultivars (Ambrosia, Cameo, Fuji, Gala, and Silken). Fertigation treatments were a factorial combination of two nitrogen (N) rates and three N application timings. N was applied at low (28 mg N/L) or high (168 mg N/L) concentrations daily at 0 to 4, 4 to 8, or 8 to 12 weeks after full bloom (wafb). Under greater N inputs, all cultivars had increased midsummer leaf and harvested fruit N concentrations, decreased fruit firmness, and in heavy crop years, decreased percent red color. Annual yield of all cultivars was significantly increased by N rate in a single year, but their cumulative yields were not different between treatments as a result of rate or timing. Altering the timing of N application within 12 wafb only affected leaf and fruit tissue N concentration. Leaf N was higher after 4 weeks of fertigation any time, although concentrations declined over the growing season, reaching minimum values around harvest. Fruit N was increased by fertigation 4 to 12 wafb. Yield, fruit firmness, and color were unaffected by fertigation timing. Critical fruit quality issues for ‘Gala’ and ‘Silken’ were small fruit size, for Ambrosia low fruit numbers, and for ‘Cameo’ soft fruit. ‘Fuji’, which achieved high yield and leaf N concentration and firm fruit, had poor red color regardless of N treatments.

Apple Root Growth, Turnover, and Distribution Under Different Orchard Groundcover Management Systems

Minirhizotrons were used to study root emergence, turnover, and depth distribution of apple (Malus ×domestica Borkh.) rootstocks (M.9/MM.111) under four groundcover management systems (GMSs)—pre-emergence herbicide (Pre-H), postemergence herbicide (Post-H), mowed sod grass (Grass), and hardwood bark mulch (Mulch)—that had been maintained since 1992 in an orchard near Ithaca, NY. Two root observation tubes were installed on both sides of one tree in three replicates for each GMS treatment. Roots were observed by camera at 2- to 3-weekly intervals during the growing seasons of 2002 and 2003 and from whole tree excavations in Apr. 2000. Tree growth and yield observations from 1992 to 2003 showed that Mulch and Post-H treatments produced more tree growth and higher yields than other treatments during most years; the Grass treatment usually had the smallest trees and lowest yields. More root emergence was observed in a light crop year (2002) than in a heavy crop year (2003). Pre-H treatment trees had more total roots and new roots than all other treatments, and trees in Grass plots had fewer total roots than others. Trees in Mulch plots had more shallow roots, and trees in Grass plots had more deep roots than others. Root diameter was positively correlated with overwintering root survival. The Pre-H treatment trees had greater root mortality than other trees during an unusually hot and dry growing season (2002) and this was attributed to higher shallow soil temperatures in this treatment. The GMS treatments affected root number and root depth distribution patterns. Despite microsprinkler irrigation, hot, dry weather conditions coincided with decreased root growth, increased root mortality, and reduced root median lifespan. GMS treatments affected root growth, turnover, and distribution at this orchard, and these differences were linked with long-term trends in tree growth and fruit production in this study.

APPLE ROOT GROWTH, TURNOVER, AND DISTRIBUTION UNDER DIFFERENT ORCHARD GROUNDCOVER MANAGEMENT SYSTEMS

Minirhizotrons were employed to study new root occurrence, turnover, and depth distribution of apple (Malus ×domestica Borkh.) rootstocks under four groundcover management systems (GMS): preemergence herbicide (Pre-H), postemergence herbicide (Post-H), mowed sod (Grass) and hardwood bark mulch (Mulch) that have been maintained since 1992 in an orchard near Ithaca, NY. Two root observation tubes were installed on both sides of one tree in three replicates for each GMS treatment. Root observations were taken at 2–3 week intervals during growing seasons of 2002 and 2003. Tree growth and yield data were collected annually since 1992. The Mulch and Post-H treatments had bigger trees and higher yields than other treatments; whereas the Grass treatment had the smallest trees and lowest yields. Higher number of new roots was observed in a light crop year (2002) than a heavy crop year (2003). Mulch trees had more shallow roots and Grass trees had fewer total roots than other treatments. Root diameter was positively correlated with overwintering root survival. The Pre-H GMS had higher root mortality during a hot and dry growing season (2002). GMS treatments affected root number and root depth distribution patterns. Hot and dry weather conditions and crop load reduced new root emergence, increased root mortality and reduced root median lifespan. GMS treatments together with environmental factors affected root growth, turnover and distribution.

Distribution, Stand Structure and Yearly Biomass Fluctuation of Elodea nuttallii, an Alien Species in Lake Biwa. Studies of Submerged Macrophyte Communities in Lake Biwa(3).

The areal distribution, stand structure and biomass of pure stands of Elodea nuttallii, an alien species of water weed invading Lake Biwa since 1961, were studied with emphasis on the remarkable yearly fluctuation in its biomass. The total area covered by the Elodea community was estimated at 895 ha, based on a complete lake survey in 1990 using sonar detection along a number of line transects. Underwater biomass samplings were carried out at two different depths in the northernmost part of the lake during two successive years, representing a light crop year (1988) and a heavy crop year (1989). The maximum biomass and stem density at the shallower site (depth 3 m) in 1989 amounted to 723g dry wt. m-2 and 4, 960 stems m-2, respectively. Those in 1988 were only 68% and 60% of the corresponding values of 1989. Both biomass and stem density decreased at the deeper sites (depth 5m), with the latter remaining fairly constant in both years. A comparison of environmental factors between light and heavy crop years indicated that a mild winter with a minimum monthly temperature above 8°C combined with sufficient sunshine in early spring favored the growth of overwintering plants from which new shoots were produced vegetatively. This resulted in greater biomass production in the following season.

Evaluation of Commercial Potential of Asian Pear Cultivars in South Carolina

An Asian pear variety trial consisting of 13 cultivars replicated 12 times was planted in 1989 near Columbia, S.C. For 6 years, cultivars were evaluated for commercial fruit production. The Chinese types `Ya Li' and `Shin Li' bloomed earliest (early March), whereas Japanese types such as `Twentieth Century' and `Choju' bloomed 10 to 12 days later. The largest trees were `Ya Li', `Shinsei', and `Shin Li', and the smallest were `Shinko', `Shinsui', and `Twentieth Century'. All cultivars on P. betulaefolia rootstock had suckers, with `Chojuro' and `Shinko' trees having the fewest. `Kosui' and `Shinsui' defoliated first each fall. Average fruit yields in kg/tree were largest for `Ya Li', `Shinsui', `Shin Li', and `Twentieth Century'. Fruit size was large (>200 g) for the Chinese types such as `Ya Li', `Shin Li', and `Daisu Li', but small (<100 g) and non-commercial for `Twentieth Century'. Fruit maturity dates were consistent year to year, with `Choju' and `Shinsui' ripening first (early July) and the Chinese types ripening last (mid-August). Low return bloom (i.e., alternate bearing) was observed after a heavy crop year. Winter injury, as evidenced by bark cracking on the southwest side of the trunk, was severe in 1993–1994. However, `Ya Li' suffered no cold damage. Fireblight was first observed in the 1992, and increased in 1993 and 1994. `Choju', `Shinseiki', and `Kosui' were the most-susceptible cultivars, while `Ya Li', `Shinsui', and `Shinko' were the most tolerant.

Seed-cone and pollen-cone production models for young black spruce seedling seed orchards: a first approximation

Seed orchard managers wanting to predict potential seed-cone (Sc) and pollen-cone (Pc) production 1 year in advance of seed release and pollen dissemination need predictive models. The present study proposes the use of cone-crop models based on tree age in young black spruce (Piceamariana (Mill.) B.S.P.) orchards. Sc and Pc production was monitored from 1987 to 1993 in each of five seedling seed orchards. Some trees began bearing Sc and Pc by tree age 6. The relationships of Sc and Pc production with tree age were each represented by three sigmoid equations: one for light crop years, one for heavy crop years, and one for light plus heavy crop years. The rate of cone increase for heavy and light crop years differed for both Sc and Pc. Sigmoid equations representing heavy Sc and Pc crop years in orchards had the highest r2 (0.8462 and 0.9381, respectively) and the lowest standard error. Sigmoid model of heavy crop years with plantation data also had the highest r2 value (0.8066) and the lowest standard error. The rate of Sc and Pc increase versus tree age was higher for orchards than for plantations. To select the best of three sigmoid models, one must take into account the early buildup phase of cone production in young trees, the yearly fluctuation in cone crops, previous-year cone production, and environmental factors that can affect cone crops.

597 PB 179 CROP LOAD-RELATED DEFORMITY OF DEVELOPING PISTACIA VERA CV KERMAN NUTS

A deformity designated as `damage by other means' (DBOM) by California pistachio processors appeared in California's San Joaquin Valley orchards in 1990. Incidence, higher during the heavy crop year of this alternate bearing cultivar, was as high as 5% of harvested yield. This represents a significant loss as DBOM nuts cannot be used for shelling stock. In 1993 ten weekly individual cluster samples from five heavily and five lightly cropped trees demonstrated a higher incidence of DBOM on heavily cropped trees. Further the damage occurred within one month of nut set, was exclusively on subterminal, adaxial positions of the rachis, and, often did not involve the nutmeat unless the deformity was extensive enough to expose the developing nutlet causing desiccation and abscission. Microanatomical studies demonstrated a deterioration of the parenchyma cells that form the inner cell layers of the endocarp (nut shell).

FOLIAR POTASSIUM SPRAY TIMING EFFECTS ON SEASONAL LEAF POTASSIUM AND PRODUCTIVITY OF FRENCH PRUNE (PRUNUS DOMESTICA)

Soil applied potassium (K) may not alleviate K deficiency in fine textured California soils when high numbers of prunes per tree are produced leading to leaf necrosis and limb death. Because K demand is increased by fruit, K nitrate (KN) sprays appear to be a corrective option for growers in this situation. Our objectives were to determine best seasonal KN spray liming strategies to minimize K deficiency, quantify K uptake into leaves after spray and to evaluate spray effects on productivity. Results indicated that regardless of spray timing leaf K was increased by approximately 0.3% and three weeks later decreased 0.2%. Average leaf K in sprayed trees was 0.7% higher than untreated trees at harvest. Fruit fresh to dry weight ratios were lower (better) from summer sprayed trees than spring. Summer KN sprayed trees had yield efficiencies equal to those having soil applied K. Fruit size was similar regardless of K application method. Foliar KN sprays may be a viable K augmentation to soil application in heavy crop years on fine textured soils.

Chemical thinning of ‘Fuji’ apples in Southern Brazil with consideration of economic aspects

Experiments were carried out using the apple cultivar ‘Fuji’ and the thinning agents NAA, NAAm, carbaryl and ethephon in single and combined sprays, adding either a non-ionic wetting agent or an emulsifiable mineral oil as an adjuvant. Economic analyses were included to select the most profitable treatments. In most thinning treatments the use of mineral oil as an adjuvant improved thinning intensity and mean fruit weight. Ethephon sprays increased fruit set in the light-crop year 1983/84, but had no thinning effect in the heavy-crop year 1984/85. However, taking into account fruit set in both years as well as potential profit, the best treatments proved to be the single sprays NAAm and NAA, applied at 8 days AFB using mineral oil as an adjuvant, and a combination spray of NAAm at FB plus 8 days followed by a later spray (FB + 21 days) of carbaryl. Both thinning agents were applied at low concentrations and with mineral oil as an adjuvant. All three treatments effectively reduced fruit set in the heavy-crop year to a fruit load density similar to that of hand-thinned trees. From an economic point of view the same treatments were superior to hand thinning when considering both years of observation.

Reduction of Mycoflora and Control of In-Shell Weevils in Pecans Stored Under High Carbon Dioxide Atmospheres

WELLS, J. M., and J. A. PAYNE. 1980. Reduction of mycoflora and control of in-shell weevils in pecans stored under high carbon dioxide atmospheres. Plant Disease 64:997-999. High carbon dioxide (C0 2) atmospheres reduced the mycoflora and controlled in-shell weevils in pecans stored under accelerated storage conditions of 7 C and 65% relative humidity. After 5 mo in atmospheres of 21% oxygen (02) and 30% CO2, pecan weevil mortality was 100%, total mycoflora isolated from kernels was significantly reduced, and off-flavors had not yet developed in the kernels. In atmospheres of 3 and 10% CO 2 (plus 21% 02) or in 1% 02 (with or without 30% CO2), weevil mortality was less than 100%. Objectionable off-flavors developed in high CO2 atmospheres after 6 mo. Alternaria and Pestalotia spp. were the fungi most frequently isolated from pecans held in air. After 5 mo in high CO2 atmospheres, Alternaria, Penicillium, and Fusarium spp. were the most frequently isolated fungi. In the southeastern United States, pecan (Carya illinoensis (Wang.) K. Koch) nuts are harvested from October to January. Much of the crop is refrigerated and stored to supply shelling plants with pecans throughout the year (11). In good crop years, refrigerated storage is an important means of holding excess supply until market conditions become more favorable to the producer. Since a heavy crop year is inevitably followed by a light crop year because of the alternate bearing nature of the pecan tree, longterm storage of pecans is also important in stabilizing the supply. Pecans are semiperishable. Highquality pecans may be held at 0-2 C for 1 yr before detectable off-flavors or rancidity develop (12). Not all pecans are of high quality at the beginning of storage, however. Late-harvested nuts may have lost freshness of flavor and the desirable light amber kernel color. Pecans may also be infested with the pecan weevil (Curculio caryae (Horn)), which damages kernels and provides avenues of invasion for postharvest storage fungi (9). Although refrigerated storage arrests the development of storage fungi and reduces damage caused by insects, it does not significantly affect survival of these organisms (5,8). Control is important, Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply approval to the exclusion of other products that also may be suitable.

Use of Prescribed Burning in Seed Production Areas to Control Red Pine Cone Beetle 13

The red pine cone beetle, Conophthorus resinosae Hopkins, is the most common of 3 insects that destroy whole cones and reduce yields in seed production areas (SPAs) of red pine, Pinus resinosa Ail. Adult beetles are on the ground for overwintering from ca. Oct. 22–ca. May 10. After low-intensity burning of naturally accumulated fuels on 0.2-ha plots gave promising adult kills, six 0.7- to 21-ha SPAs were treated by backfire or strip-head fire burning in Minnesota, Wisconsin, and Michigan. Conophthorus infestation was greatly reduced in burned SPAs 4 ha and larger, and cones free of all cone destroyers were significantly increased in 4 SPAs by 11–45%. Combined infestation by the red pine cone moth, Eucosma monitorana Heinrich, and the red pine cone worm, Dioryctria disclusa Heinrich, went up or down after treatment depending on several factors. Adverse Eucosma-Dioryctria infestation behavior was minimized when SPAs with heavy cone crops were treated. Burning areas of sufficient size in heavy crop years the fall or spring before harvest seems a promising way to protect SPA crops from cone destroying insects.

Control of alternate cropping of Valencia orange with ethephon and napthalene acetic acid

Three experiments were done in the Riverland district of South Australia with the aim of controlling alternate cropping of mature Valencia orange trees by chemical thinning. In experiment 1, 300 p.p.m. ethephon was applied in either October, November or December. In experiment 2, sprays of either 200, 250, 300 or 350 p.p.m. ethephon were applied in late November. In experiment 3, sprays of either ethephon, NAA or a mixture of both were applied in early December. Sprays of ethephon in December were more effective than in October, and resulted in a 40 per cent reduction of mature fruit weight in a heavy crop year. All concentrations of ethephon of 250 p.p.m, or more reduced the heavy crop load, and in the following year increased light crops. A 15 per cent reduction in crop load following sprays of 250 p.p.m, gave even cropping trees. Treated trees produced, over two years, 10 per cent more fruit weight than control trees. Fruit from treated trees were larger in the heavy crop year and smaller the following year. In the third experiment, 300 p.p.m. ethephon reduced the mature crop by 31 per cent and 500 p.p.m. NAA reduced it by 18 per cent. A mixture of the two chemicals effected a 51 per cent reduction in crop load, but the NAA did not significantly reduce leaf drop. NAA at 500 p.p.m. resulted in the most even cropping trees.

Correlation Among Growth, Yield, and Nutritional Factors for Pecan (Carya illinoesis W. cv. Stuart): Correlations with Yield, Quality, and Terminal Shoot Growth1

Abstract Correlations between pecan yield, quality, tree growth, and various nutritional variables were studied over an 8-year period. Yield was negatively correlated with yield the previous year, but yield was positively correlated with yield accumulated over several years. Terminal shoot growth and nuts/lb. varied in a pattern similar to yield. Soil and leaf analysis was not often correlated with yield, nut quality, or tree growth. Degree of leaf retention in a heavy crop year was positively correlated with yield the following season.

Effects of Crop Load, Girdling, and Auxin Application on Alternate Bearing of the Pistachio1

Abstract Alternate bearing in the pistachio, in contrast to other tree fruit species, is caused by abscission of abundant inflorescence buds during the heavy crop year. Bud abscission was found to increase as the number of nuts per branch increased. Branch girdling between the developing nuts on 1-year-old wood and the inflorescence buds on current wood reduced bud abscission to practically the same extent as that resulting from removing the young nuts from the branches. Application of para-chlorophenoxyacetic acid delayed but did not alter the degree of bud abscission. The greater the crop load in 1970, the shorter the shoot growth in length in 1971.