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1.
A complete dynamic model was developed to describe the effects of soil water potential (WP) on the growth and external quality of standard cut chrysanthemum (Chrysanthemum morifolium) in order to optimise water management of greenhouse crops. Experiments using chrysanthemum cv. ‘Jinba’ with different planting dates and levels of water treatment were conducted in a lean-to type greenhouse from 2006 to 2008. The dynamics of leaf area index (LAI), dry matter partitioning, and external quality traits (plant height, number of leaves per plant, flower-head diameter and peduncle length) were first determined as functions of accumulated photothermal index (PTI). Impacts of WP on leaf photosynthetic rate, LAI, dry matter partitioning, and the external quality traits were quantified via introducing the experimentally identified effects of WP on the parameters in the light response curve of leaf photosynthetic rate and the PTI-based functions. These quantitative relationships were incorporated into a generic crop growth model SUCROS. Using independent experimental data, the model was found to give good predictions for biomass production, dry weight of organs, and the external quality traits of the chrysanthemum cultivar grown under different levels of water supply. The coefficient of determination (r2) between the predicted and measured results was 0.91 for LAI, 0.88 for biomass production, and varied between 0.83 and 0.93 for organ dry weight and the external quality traits. Further evaluation is needed when applying this model to a wider range.  相似文献   

2.
Summary

A dynamic simulation model for onion growth at potential production level (ALCEPAS), presented in a previous paper, was validated using data on leaf area index, bulb and green leaf dry-matter production, bulb formation and day of fall-over from independent trials at four locations. The model performance in terms of bulb dry-matter production was good under environmental conditions close to the optimum, but insufficient under stress situations. The model overestimated leaf area index and green leaf dry matter. Bulb formation was simulated satisfactorily, while the time of 50% fall-over was simulated too early at low plant densities.  相似文献   

3.
Summary

The effect of irrigation rate under various crop loads on the fruit size of apple (Malus domestica Borkh cv. Golden Delicious) was investigated in three field experiments in 1993–1995. During the first two years the field experiments evaluated the effects of various crop loads on yield, fruit size and midday stem water potential under 40% deficit irrigation. In 1995, the effects of five irrigation levels (0.42–1.06 of USDA Class A evaporation pan) and four crop loads (100–450 fruits per tree) were studied in a factorial experiment. Midday stem water potential increased with irrigation level and decreased with crop load in 1993 and at the lowest irrigation level in 1995. Daily fruit growth rate decreased with midday stem water potential in 1993 and at the lowest irrigation level in 1993. The effect of crop load on fruit growth rate was associated with limited soil water availability. A reduction in yield and average fruit size were associated with midday stem water potentials lower than –1.3 MPa. Taking an additional 0.1 MPa as a safety factor, –1.2 MPa could serve as a reasonable threshold for irrigation control in the orchard.  相似文献   

4.
Summary

A model for describing the modification of soil and air temperature by nonwoven polypropylene has been developed. Such a model takes into account the first two harmonics of the Fourier series determined from the normalized data of soil and surface temperature. The numerical model predicts with accuracy the soil thermal regime for hourly and daily intervals throughout the crop production cycles of Chinese cabbage (Brassica campestris ssp. pekinensis), lettuce (Lactuca sativa), table beet (Beta vulgaris) and spinach (Spinacia oleracea). Furthermore, the model proposed by Parton (1984) has been modified to estimate the surface temperature based on data of temperature measured at 2.m height, biomass and global solar radiation flux density incident on the crop grown under nonwoven polypropylene conditions.  相似文献   

5.
Larsen  Ashley E.  McComb  Sofie 《Landscape Ecology》2021,36(1):159-177
Context

Global environmental change is expected to dramatically affect agricultural crop production through a myriad of pathways. One important and thus far poorly understood impact is the effect of land cover and climate change on agricultural insect pests and insecticides.

Objectives

Here we address the following three questions: (1) how do landscape complexity and weather influence present-day insecticide use, (2) how will changing landscape characteristics and changing climate influence future insecticide use, and how do these effects manifest for different climate and land cover projections? and (3) what are the most important drivers of changing insecticide use?

Methods

We use panel models applied to county-level agriculture, land cover, and weather data in the US to understand how landscape composition and configuration, weather, and farm characteristics impact present-day insecticide use. We then leverage forecasted changes in land cover and climate under different future scenarios to predict insecticide use in 2050.

Results

We find different future scenarios—through modifications in both landscape and climate conditions—increase the amount of area treated by ~ 4–20% relative to 2017, with regionally heterogeneous impacts. Of note, we report large farms are more influential than large crop patches and increased winter minimum temperature is more influential than increased summer maximum temperature. However, our results suggest the most important determinants of future insecticide use are crop composition and farm size, variables for which future forecasts are sparse.

Conclusions

Both landscape and climate change are expected to increase future insecticide use. Yet, crop composition and farm size are highly influential, data-poor variables. Better understanding of future crop composition and farm economics is necessary to effectively predict and mitigate increases in pesticide use.

  相似文献   

6.
Summary

The aim of this work was to assess the influence of three levels of aeration of the nutrient solution (high, low, or no aeration) on the growth and quality of two cultivars of purslane (Portulaca oleracea L.): the commercial cultivar, ‘Golden Purslane’, and a local Spanish accession, C-215. Both were grown in a floating system over four crop cycles. Our results showed purslane to be a crop that exhibited little sensitivity to oxygen depletion in the rooting medium, since it was able to adapt to a gradual reduction in oxygen content. Under such conditions, purslane plants created an aerenchyma tissue (equivalent to approx. 10% of root sections in the non-aerated treatments in both cultivars) that helped to maintain growth. Under conditions in which no aeration was provided, there was a slight decrease in plant growth. The final quality of the product was improved because leaf nitrate concentrations were reduced (by more than 1,300 mg kg–1 FW) compared with the high aeration treatment, and the content of functional phytochemicals and SPAD values (chlorophyll contents) were increased.  相似文献   

7.
Summary

At the standard recommended density of 1666 plants ha?1, the influence of rectangular (3 m rows×2 m in the row), hedgerow (4×1.5 m) and tramline (6 m rows alternating with 2 m rows × 1.5 m) plant spacings was investigated on the growth and productivity of ‘Williams’ banana over five cropping cycles. There were no significant differences in pseudostem or leaf morphology, leaf emergence rate or crop cycle duration between spacings. There were also no bunch mass differences between spacings in the P and R1 cycles, whereas in the R2, R3 and R4 cycles, tramline bunches were respectively 7.6, 7.0 and 9.0% smaller than those from rectangular-spaced plants (P<0.05 in the R4). Overall productivity (yield per annum) was similarly reduced by 7.4% from rectangular to tramline plantings, although this was not significant. Productivity of the hedgerow plantings was intermediate at 4.6% less than the rectangular.  相似文献   

8.
TOMSIM(l.O) and TOMGRO(l.O) are two dynamic models for tomato growth and development. Their submodels for dry matter production are compared and discussed. In TOMSIM(l.O), dry matter production is simulated by a modified version of SUCROS87 (Spitters et al., 1989). Single leaf photosynthesis rates are calculated separately for shaded and sunlit leaf area at different depths in the canopy, according to the direct and diffuse components of light; daily crop gross assimilation rate (A) is computed by integration of these rates over the different depths and over the day. In TOMSIM(l.O) leaf photochemical efficiency (e) and potential leaf gross photosynthesis rate at saturating light level (Pgmax) both depend on temperature and C02 level. In TOMGRO(l.O) crop gross photosynthesis rate is calculated by the equation of Acock et al. (1978); e is a constant and Pg max is a linear function of C02. In both models leaf photosynthesis characteristics are assumed to be identical in the whole canopy. Maintenance respiration (Rm) and conversion efficiency (Cf) are taken into account in the same way, except that root maintenance respiration is neglected in TOMGRO(l.O). For both models a sensitivity analysis was performed on the input variables (light intensity, temperature, C02 and leaf area index (LAI)) and on some of the model parameters. Under most conditions considered, simulated A was found to be 5-30% higher in TOMSIM(l.O) than in TOMGRO(l.O). At temperatures above 18°C Rm was also higher in TOMSIM(l.O), and C, was 4% higher in TOMGRO(l.O). The two models were very sensitive to changes in e and to a lesser extent to changes in the light extinction coefficient, whereas the scattering coefficient of leaves had hardly any effect on the simulated A. TOMGRO(l.O) appeared to be rather sensitive to the C02 use efficiency, whereas at ambient C02 level mesophyll resistance was quite important in TOMSIM(l.O). Four sets of experimental data (differences in cultivar, C02 enrichment and planting date) from Wageningen (The Netherlands) and Montfavet (southern France) were used to validate the models. Average 24 h temperature and average daily C02 concentration values were used as input to the models. For the Wageningen experiments, hourly PAR values were calculated from the daily global radiation sum by TOMSIM(l.O) and used as input in both models. For the Montfavet experiment, average hourly PAR measurements were used. Also measured LAI, dry matter distribution and organ dry weights (for calculation of Rm) were input to the simulation. In the Wageningen experiments, total dry matter production was simulated reasonably well by both models, whereas in the Montfavet experiment an under-estimation of about 35% occurred. TOMGRO(l.O) and TOMSIM(l.O) simulated almost identical curves in all four experiments. Strong and weak points of both models are discussed.  相似文献   

9.
Summary

The effect of crop load on the growth dynamics of individual shoots was analysed in apricot trees in the third growing season, comparing their development at two initial locations along the bearing branch. Growth dynamics were observed throughout the growing season, from April to August, and took into account both primary growth (i.e..number of expanded leaves) and secondary growth (i.e. basal diameter increment). Crop load influenced primary growth rhythmicity and more precisely growth resumption within the growing season. The length of the growing period and the number of expanded leaves were more signi®cantly reduced on shoots originated from a proximal position along the branch than in a distal position. Thus, crop load enhanced the acrotonic distribution of branching. The allometric relationship between the basal diameter and the number of expanded leaves per shoot was not dependent upon shoot type, location or crop load treatment. Arguments are provided supporting the hypothesis that cambial growth occurring soon after the expansion of the preformed leaves is responsible for cessation of primary growth. This competition was shown to be independent of crop load and to involve only vegetative organs. These results indicate that the sink demand of the secondary growth and the resulting competition with the primary growth should be taken into account in the carbon economy of fruit trees, and that the competition between organs is not equally distributed between the organs of a given type but depends on their relative location.  相似文献   

10.
Abstract

In the mild winter regions strawberries are the most important crop of the small fruits. Strawberry production systems rely on the ‘winter’ planting system developed in California for early production and predominantly on California cultivars with plants set at high densities. The aim of this paper is to provide a brief review of strawberry growth and development in the mild winter regions based on a review of the literature and on research studies carried out in southwestern Portugal.  相似文献   

11.
A field experiment was carried out in 1996/1997 and repeated in 1997/1998 at the Jordan University Research Station located in the central Jordan Valley to determine the effect of weed competition on growth and yield of cauliflower Brassica oleracea var. botrytis cv. “White Cloud”. The treatments consisted of either allowing weeds to infest the crop or maintaining plots weed-free for increasing durations after transplanting. Results showed that longer periods of weed/cauliflower competition greatly reduced crop growth and head yield. Average reductions in shoot dry weight and head yield were 81% and 89%, respectively. Maintaining a weed-free crop for any period after transplanting increased cauliflower growth and head yield compared with the weed-infested control. Weed competition for 14 days after transplanting reduced cauliflower average head yield by 41%. To determine the critical period of weed competition and the influence of weed infestation on cauliflower head yield the Gompertz and logistic equations were fitted to data representing increasing duration of weed-free and weed-infested periods, respectively. Based upon an arbitrary 5% level of head yield loss, the critical period of weed competition occurred at 0–38 days after cauliflower transplanting which corresponded with the rapid increase in weed biomass. Results indicated that early weed removal is necessary to prevent yield loss.  相似文献   

12.
Summary

The influence of plantation age and plant density on pseudostem size, canopy cover and vegetative growth characteristics of banana cv. Williams was investigated over four cropping cycles at Burgershall Research Station, in the subtropical Eastern Transvaal. Densities were 1000, 1250, 1666 and 2222 plants ha?1. Over all densities, pseudostem height, lamina area, numbers of functional leaves at flowering and LAI increased with plantation age up to the second ratoon (R2). This increase in canopy cover caused vegetative and total cycle intervals to be extended progressively from plant crop to R3. Within cycles, higher density had little effect on plant height or lamina length, but induced thinner plants with significantly narrower leaves than at low density. Peak ratoon LAI at flowering almost doubled between 1000 and 2222 plants ha?1. At 1000 plants ha?1, four cropping cycles were completed in the same period as three cycles at 2222 plants ha?1. Annual leaf emergence rate was significantly reduced by up to five leaves with an increase in plant density from 1000 to 2222 plants ha?1, which was also accompanied by a 3–4°C reduction in pseudostem temperature. Up to six more leaves per plant were produced at 2222 plants ha?1 and only 14% of the available radiation was transmitted through the primary canopy compared with 30% at 1000 plants ha?1. Crop cycle interval is an important component of annual yield at different densities.  相似文献   

13.
Summary

Rates of fruit growth, on-vine changes in the soluble and insoluble carbohydrate pools, and subsequent changes during storage were examined on kiwifruit from vines having moderate to very high crop loads (20–50 fruit m?2). In accord with previous studies, vines carrying the highest loads exhibited a 18% decrease in mean fruit weight and a two-fold increase in total yield compared with those having the lowest crop loads. Rates of dry-matter accumulation in the fruit varied in proportion to total yield and remained constant over the entire season – a result that deserves further investigation. Effects of crop loading on the carbohydrate composition of fruit were small and after reviewing the available literature we conclude that the primary determinants of fruit composition are genetic and climatic. Relationships between the various fruit quality variables were used to develop a predictive model of soluble solids concentration of fruit at eating ripeness from harvest measurements of fruit density (weight per unit volume) or dry matter. The accuracy of these predictions are of the order of 1% (w/v). The rate of change in soluble solids during storage at 0°C is shown to follow a simple exponential function of time with a time constant of 20 d.  相似文献   

14.
Summary

As a crop new to the western world, opportunities for production of Chinese water chestnut have barely been exploited. In China, over the latitude range 21º to 34ºN it is planted in spring and harvested in autumn. Opportunitiesexist to extend its cultivation to new climates, where growth throughout the year is not constrained by low temperature, but may be constrained by photoperiod. To study the response of Chinese water chestnut to photoperiod, six experiments wereconducted intropical central Queensland. One set focussed on planting early in spring, with long-day treatments superimposed. Anotherset investigated autumn and winter plantings, also with superimposed long-days, and the third compared the performance ofChinese water chestnut under constant or decreasing photoperiods, ranging from 8.h to 20.h, in light-out chambers. Corm formation was strongly retarded by long days but promoted by the photoperiods which were shorter than a criticalmaximum. Thecritical photoperiod was between 12.0±12.5.h, below which corm formation was rapid, and above which it was non-existent, or minimal if combined with cool (<21º mean) temperature. Under short days, to the detriment of stem growth, significantly more dry matter was allocated to corms and rhizomes. The latter provided potential corm sites. The response of corm formation and rhizome production to photoperiods shorter than the critical was more pronounced the moreextended the treatment period. The data provide evidence for the ability to manipulate timing of harvest at the field scale to extend availability of fresh produce on the market.  相似文献   

15.
Summary

This review aims to describe the nature of effective microorganisms (EM) and how EM influence the growth, yield, quality, and protection of vegetable plants. EM comprise a mixture of live natural cultures of microorganisms isolated from fertile soils that are used to improve crop production. EM technology was developed over 40 years ago by Dr. Tero Higa in Japan. How EM act and interact in the soil-plant environment to suppress plant pathogens and disease, to conserve energy, to solubilise soil minerals, to aid the balance and ecology of soil microbes, and to improve photosynthetic efficiency and biological nitrogen fixation are described. In 70% of published studies, it was concluded that EM had a positive effect on the growth of vegetables, while, in the other 30%, they had no significant influence. In this investigation, among 22 reports on the effects of EM on the yields of vegetables, 84% were positive, 4% were negative, and 12% showed no significant influence. It is concluded that EM can improve the quality and yield of vegetables by reducing the incidence of pests and diseases, and by protecting against weeds, thereby contributing to sustainable agriculture.  相似文献   

16.
Eight-year-old trees of Laxton’s Superb apple on M.II rootstock growing on loamy fine sand of low moisture retention were used to study growth and crop responses to different soil moisture conditions from 1953 to i960 inclusive. Water was applied when soil moisture tensiometers set at 1 ft. depth indicated tensions of : A, 10 cm. Hg ; B, 20 cm. Hg ; C, 50 cm. Hg. Treatment D was unwatered.

Water was applied to an area 12 ft. in diameter around each tree, which was about one-third of the ground area available to each tree. The average amount of water required by each treatment during a season was equivalent to : A, 4-1 ; B, 3-5 ; C, 2-1 inches over its whole area.

Comparison of soil moisture deficits in the unwatered plots in the very dry season of 1959 with amounts of water applied to the other trees suggested that the rate of water loss throughout the experiment was not seriously affected by the treatments applied.

The water treatments stimulated trunk and shoot growth ; growth differences between differently treated trees could be adequately explained in terms of soil moisture tension and root-occupied soil volume. Evidence was found of serious leaching under the wettest treatment, and this may have caused a lower growth and crop response to treatment A than to B in the later years of the trial.

Crop increases were directly related to growth increases. Despite the marked effects of water treatments on shoot numbers and on crop increase the growth and crop relationship was virtually unchanged.

Treatments A, B and C increased total crops by 40%, 46% and 25% respectively, and marketable crops by 44%, 55% and 42% respectively. There was no marked effect of treatment on fruit size, though the increased proportion of fruit of a commercial size from the watered trees was of importance. Treatment B provided the largest total and marketable crops, but treatment C provided the greatest increase in marketable crop for each inch of water applied.  相似文献   

17.
Summary

The daily patterns of vascular and transpiration flows to and from peach fruit were compared between heavily-thinned (LCL) and unthinned (HCL) trees, in order to assess when these flows were limited by resource availability (source-limited) or by the genetic potential of the fruit (sink-limited) during the day. Minute variations in fruit growth and in phloem, xylem, and transpiration flows were determined at cell division (stage I) and at cell expansion (stage III) during fruit development on several fruit per treatment, using highly sensitive fruit gauges. During cell expansion, the thinning treatments were also compared for their effects on fruit water potential. At stage I, no difference between treatments was found in any of the flows, suggesting that fresh matter (FM) import from phloem and xylem is sink-limited during early fruit development. At stage III, HCL fruit were smaller and had higher specific transpiration rates during the day. Xylem flow did not show any source limitations due to high crop load. However, it was “sink-strengthened” in the afternoon, in HCL, as these fruit reached lower water potentials during the day. Phloem flow to HCL fruit was source-limited during the afternoon, and at night, due to fruit-to-fruit competition. However, HCL fruit appeared to take advantage of their lower water potential at midday, when they showed higher rates of phloem flow. Although daily growth in HCL fruit undergoes periods of source limitation, this study showed how, at certain times of day, fruit may be more active sinks in attracting resources in high cropping conditions than at low crop loads.  相似文献   

18.
Summary

The dependence between flowering cycles and woody stem parts of a rose crop was studied, with respect to plant architecture and carbohydrate content. Two harvesting methods (“control” versus “flush”) and two plant types (“control” versus “one stemmed”) were compared. Crop growth and partitioning of dry matter were studied as influenced by crop management during 18 months of culture. For a full-productive year, flush harvesting generally promoted bud break as compared with continuous harvesting but at the same time, also due to lower light interception, blind-shoot formation was enhanced and the individual flower weight reduced. Numbers of basal shoots were hardly related to flower production over a full cropping year. Flower production was much more sensitive to the number and diameter of branches at the height of cutting the flowers. The treatments did not affect carbohydrate allocation in the plant. Total carbohydrate storage was much too low to argue a clear role for the possible use of movement of carbohydrate reserves towards new growth. Maximum starch concentration was found at the beginning of summer and gradually dropped to a minimum in December and then increased again to a spring maximum. A cold treatment did increase the total non-structural carbohydrate (TNC) concentration but no positive influence on new basal-shoot formation was observed. No starch gradient was found in basal stem parts.  相似文献   

19.
Summary

The timing of fungicide and antibiotic applications in fruit crops often overlaps flowering and pollination. Numerous studies report detrimental effects of chemical applications on pollination, fruit set and yield. However, field results can be quite variable even when similar compounds are tested on the same crop. Problematic is that field variables unrelated to the effects of pesticides on reproductive activities can mask results. In the current study, we specifically investigated the effects of selected pesticide sprays applied to stigmas, on subsequent pollen germination and tube growth. Using two model systems, apple and almond, sprays were applied to detached emasculated flowers under constant laboratory conditions using an electronically controlled robotic apparatus which simulated a field sprayer. flowers were pollinated at specific times after spraying, and pollen tube numbers and growth assessed using fluorescence microscopy. The pesticides evaluated were for apple: captan, myclobutanil and streptomycin; and for almond: azoxystrobin, myclobutanil, iprodione and cyprodinil. In apple, captan significantly reduced pollen germination, by 20% compared with water controls when pollination was conducted 18 h after treatment. The number of tubes that reached the basal part of the style within 20 h was not affected. In contrast, myclobutanil and streptomycin had no significant effect on pollen tube growth. With almond, none of the sprays significantly affected pollen germination or tube growth.  相似文献   

20.
Summary

‘Elstar’ is the latest-maturing commercial apple cultivar grown in Norway, with high fruit quality when properly managed. In May 2006, an experiment with four different crop loads [2, 4 ,6, or 8 flowers or fruitlets cm–2 trunk cross-sectional area (TCSA), respectively] was established at two different stages [first bloom (FB), or 20-mm diameter fruitlets] and compared to unthinned control trees. Fruit growth was measured on individual fruit for each treatment throughout the season at weekly intervals. Thinning at FB gave a significantly lower final percentage fruit set than thinning to the same cropping level at the 20-mm fruitlet stage. However, fruit weights and soluble solids contents (SSC) were significantly higher, and the background fruit colour improved when trees were thinned at FB. The final number of fruit at harvest was less than the amount established at FB, or at the 20-mm fruitlet stage. There were significant differences between treatments in final fruit numbers per TCSA, which reflected the different crop loads. Fruit weights and SSC values were highest with the lowest crop load, and decreased with increasing crop loads. There was also a strong crop-load effect on the extent of return bloom per tree in the subsequent year. Trees thinned at FB had significantly more flower clusters than those thinned at the 20-mm fruitlet stage of. Untreated control trees had the lowest number of flower clusters. The amount of return bloom declined with increasing crop load. Second year crop loads and fruit weights were highest when trees were thinned at FB to two or four apples cm?2 TCSA in the previous year. Trees with the highest crop load had the lowest crop load in the following year. Fruit quality was generally high for all treatments.  相似文献   

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