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991.
Agronomic response and water productivity of almond trees under contrasted deficit irrigation regimes 总被引:1,自引:0,他引:1
Gregorio Egea Pedro A. Nortes María M. Gonzlez-Real Alain Baille Rafael Domingo 《Agricultural Water Management》2010,97(1):171-181
We investigated the long-term effects of different deficit irrigation (DI) options on tree growth, shoot and leaf attributes, yield determinants and water productivity of almond trees (Prunus dulcis, cv. Marta) grown in a semiarid climate in SE Spain. Three partial root-zone drying (PRD) irrigation treatments encompassing a wide range of water restriction (30%, 50% and 70% of full crop requirements, ETc) and a regulated deficit irrigation treatment (RDI, at 50% ETc during kernel-filling) were compared over three consecutive growth seasons (2004–2006) to full irrigation (FI). The results showed that all deficit irrigation treatments have a negative impact on trunk growth parameters. The magnitude of the reduction in trunk growth rate was strongly correlated through a linear relationship with the annual volume of water applied (WA) per tree. Similarly, a significant relationship was found between WA and the increase in crown volume. In contrast, leaf-related attributes and some yield-related parameters (e.g., kernel fraction) were not significantly affected by the irrigation treatments. Except in PRD70, individual kernel weight was significantly reduced in the deficit irrigated treatments. Kernel yield, expressed in percent of the maximum yield observed in the FI treatment, showed a linear decrease with decreasing WA and a slope of 0.43, which implies that a 1% decrease in water application would lead to a reduction of 0.43% in yield. Water productivity increased drastically with the reduction of water application, reaching 123% in the case of PRD30. Overall, our results demonstrate the prevalence of direct and strong links between the intensity of the water restriction under PRD – i.e., the total water supply during the growing season – and the main parameters related to tree growth, yield and water productivity. Noteworthy, the treatments that received similar annual water volumes under contrasted deficit irrigation strategies (i.e., PRD70 and RDI) presented a similar tree performance. 相似文献
992.
Sharp-crested weirs are the simplest form of over-flow spillway that commonly used to determine the flow rate in hydraulic
laboratories, industry and irrigation systems, where highly accurate discharge measurements are needed. In this study, the
experimental upper and lower nappe profiles in rectangular sharp-crested weirs are fitted by quadratic and cubic equations,
respectively. In addition, free-vortex theory is used to simulate flow over this kind of weirs and determine discharge coefficient.
Physical models of sharp-crested weirs with various widths and heights were considered. The proposed method agrees well with
the experimental observations. Also, the experimental data indicate that the suggested equation presents reasonable results
for the range of 0 < h/P < 9. 相似文献
993.
<正>管理学家德鲁克指出,基于顾客,企业只有两项最基本的职能:营销和创新。在当下农机行业进入存量竞争阶段,想要跳出同质化的红海,创新和营销变得特别重要。2019年已过去,但它留下的印记却是深刻的,尤其是在农机营销领。笔者为大家整理出过去一年农机行业有重大影响的营销事件。 相似文献
994.
Optimizing yield,water requirements,and water productivity of aerobic rice for the North China Plain 总被引:1,自引:0,他引:1
Changying Xue Xiaoguang Yang Bas A. M. Bouman Wei Deng Qiuping Zhang Weixiong Yan Tianyi Zhang Aji Rouzi Huaqi Wang 《Irrigation Science》2008,26(6):459-474
Water resources for agriculture are rapidly declining in the North China Plain because of increasing industrial and domestic
use and because of decreasing rainfall resulting from climate change. Water-efficient agricultural technologies need to be
developed. Aerobic rice is a new crop production system in which rice is grown in nonflooded and nonsaturated aerobic soil,
just like wheat and maize. Although an estimated 80,000 ha are cultivated with aerobic rice in the plain, there is little
knowledge on obtainable yields and water requirements to assist farmers in improving their management. We present results
from field experiments with aerobic rice variety HD297 near Beijing, from 2002 to 2004. The crop growth simulation model ORYZA2000
was used to extrapolate the experimental results to different weather conditions, irrigation management, and soil types. We
quantified yields, water inputs, water use, and water productivities. On typical freely draining soils of the North China
Plain, aerobic rice yields can reach 6–6.8 t ha−1, with a total water input ranging between 589 and 797 (rainfall = 477 m and water application = 112–320 mm). For efficient
water use, the irrigation water can be supplied in 2–4 applications and should aim at keeping the soil water tension in the
rootzone below 100–200 kPa. Under those conditions, the amount of water use by evapotranspiration was 458–483 mm. The water
productivity with respect to total water input (irrigation plus rainfall) was 0.89–1.05 g grain kg−1 water, and with respect to evapotranspiration, 1.28–1.42 g grain kg−1 water. Drought around flowering should be avoided to minimize the risk of spikelet sterility and low grain yields. The simulations
suggest that, theoretically, yields can go up to 7.5 t ha−1 and beyond. Further research is needed to determine whether the panicle (sink) size is large enough to support such yields
and/or whether improved management is needed. 相似文献
995.
José AlvesJr Marcos V. Folegatti Larry R. Parsons Wije Bandaranayake Claudio R. da Silva Tonny J. A. da Silva Luís F. S. M. Campeche 《Irrigation Science》2007,25(4):419-428
The expansion of permanent trickle irrigation systems in Sao Paulo (Brazil) citrus has changed the focus of irrigation scheduling
from determining irrigation timing to quantifying irrigation amounts. The water requirements of citrus orchards are difficult
to estimate, since they are influenced by heterogeneous factors such as age, planting density and irrigation system. In this
study, we estimated the water requirements of young ‘Tahiti’ lime orchards, considering the independent contributions from
soil evaporation and crop transpiration by splitting the crop coefficient (Kc = ETc/ETo) into two separate coefficients; Ke,
a soil evaporation coefficient and Kcb, a crop transpiration coefficient. Hence, the water requirement in young ‘Tahiti’ lime
(ETy) is ETy = (Ke + Kcb) · ETo, where ETo is the reference crop evapotranspiration. Mature tree water requirement (ETm) is ETm = Kcb · ETo, assuming no soil water evaporation. Two lysimeters were used; one was 1.6 m in diameter and 0.7 m deep, and
the other was 2.7 m in diameter and 0.8-m deep. The first one was used to calculate evaporation and the second one was used
for transpiration. ETo was estimated by the Penman–Monteith method (FAO-56). The measurements were conducted during a period
between August 2002 and April 2005 in Piracicaba, Sao Paulo state, Brazil. The lysimeters were installed at the center of
a 1.0-ha plot planted with ‘Tahiti’ lime trees grafted on ‘Swingle’ citrumelo rootstock. The trees were 1-year old at planting,
spaced 7 × 4 m, and were irrigated by a drip irrigation system. During the study period, Kc varied between 0.6 and 1.22, and
Kcb varied between 0.4 and 1.0. The results suggested that for young lime trees, the volume of water per tree calculated by
Ke + Kcb is about 80% higher than the volume calculated using Kc. For mature trees, the volume of water per tree calculated
using just Kcb can be 10% less than using Kc. The independent influence of soil evaporation and transpiration is important to better understand the water consumption of
young lime trees during growth compared to mature lime trees. 相似文献
996.
We investigated the effects of partial root-zone drying (PRD) applied at different periods on leaf water relations, vegetative development, fruit yield, must and wine quality in wine grapes (Vitis vinifera L. cv. Monastrell) during a 3-year field experiment in order to determine the importance of the timing of PRD application on physiological and agronomical vine response under semiarid conditions. Two irrigation treatments were applied: conventional drip irrigation (CI) and PRD. Both treatments received the same annual water quantity. Each year the PRD treatment was applied at different periods of the growth cycle. In 1999 PRD was applied from veraison to harvest (end July–early September); in 2000 from fruit set to harvest (mid June–early September); and in 2001 PRD from budburst to harvest (mid April–early September). Leaf water relations and gas exchange during the experimental period were not significantly affected by PRD treatment. In 1999 and 2000 there was no significant treatment effect on vegetative development, yield or fruit quality. However, in 2001 (when PRD was applied from budburst to harvest), reproductive and vegetative development was clearly altered in PRD vines. Fruit set percentage and vegetative development (shoot length, pruning weight and primary and lateral leaf area) were significantly increased in PRD vines compared to CI. This resulted in both higher yield (kg per vine) (43%) and water use efficiency (40%) compared to CI vines. Berry number per cluster and cluster weight were also significantly increased in PRD vines. Notwithstanding higher yield in PRD vines and a similar berry size, the must and wine quality was not significantly altered, indicating a higher synthesis and accumulation of photoassimilates and metabolites in the berries of PRD vines. We conclude that there was an positive effect on vegetative and reproductive growth when long-term PRD was applied from the beginning of growing season (budburst), suggesting that early onset of PRD is desirable to intensify PRD response under these semiarid conditions. Nevertheless from these results we need to further investigate the long- and short-term effects of PRD, with moderate water amounts, on vegetative and reproductive development such as flowering and fruit set processes in wine grapes. 相似文献
997.
The standardized ASCE Penman–Monteith and FAO-56 equations were used to estimate reference evapotranspiration (ET0) using estimated and measured net radiation (Rn) and soil heat flux (G), based on hourly and daily meteorological data. The estimates were evaluated against lysimeter measurements. The results indicate that using measured or estimated values of Rn and G can have significant effect on the accuracy of the ET0 estimations, especially when calculations were made on an hourly basis. The FAO-56 version performed very well during the irrigation season on a daily basis. The use of measured Rn and G did not improve ET0 estimation on a daily basis, therefore, the use of estimated Rn and G appears to be dependable when calculations are based on 24-h weather data. When daily ET0 was calculated from hourly estimations, the results were different depending on the version used. The ASCE version was more accurate, especially when Rn and G were measured. Therefore, measurement of Rn and G may have potential to improve estimation only when daily ET0 is calculated from hourly estimations. The PM FAO-56 version was always a little less accurate than the ASCE version. For hourly calculations, using a constant surface resistance (as in FAO-56 version), the PM method underpredicted for high evaporative demand and vice versa. The ASCE version performed better than PM FAO-56 version when Rn and G were measured and estimated. Therefore, ASCE version tended to provide quite accurate values of hourly ET0, even using estimated values of Rn and G. As conclusion, the methods proposed by FAO-56 for estimating Rn and G tended to produce accurate estimates for daily and hourly ET0 under semiarid conditions and can be used with some degree of confidence for estimating ET0. In addition, results suggest that the ASCE standardized equation on an hourly basis improved the accuracy of ET0 estimation with respect to the FAO-56 version. 相似文献
998.
The uniform and precise application of microbial particles close to the target organism and to the plant to be protected can
increase the success of a biological control treatment. The use of systems or technologies which are usually available in
agriculture could influence the acceptability of biocontrol agents by farmers, and enlarge the market. A pilot system was
realized using dripper lines, drippers, filters and other tools commonly used in irrigation and precision agriculture in the
greenhouse to evaluate their suitability for applying and distributing microbial biocontrol agents. Conidial suspensions of
marketed or marketable agents were used, i.e. Fusarium oxysporum, F. solani, Trichoderma harzianum and Paecilomyces lilacinus. The experiments carried out demonstrated that conidial suspensions (106 conidia ml−1) can pass through the drippers without causing clogging, regardless of their size, and remained viable. The term ‘microbigation’
is here proposed for this kind of microbial application technique. 相似文献
999.
Antonino De Lisi Vincenzo Montesano Donatella Negro Giulio Sarli Emanuela Blanco Gabriella Sonnante Gaetano Laghetti 《Genetic Resources and Crop Evolution》2014,61(4):853-859
Ten accessions of wild Borago officinalis were collected during missions in the course of a research activity carried out on plants producing nutraceutical compounds. The aim was to identify populations that produce a higher content of γ-linolenic acid, as this compound has important therapeutic properties and has been used in medical tests to treat rheumatoid arthritis, eczema, and psoriasis with good therapeutical results. The present study reports on the characterization of both the polyunsaturated fatty acid composition and on genetic diversity estimated by means of AFLP markers in several B. officinalis accessions collected in Southern Italy and grown in isolation by means of screen houses specifically designed for each single population. Polyunsaturated fatty acid were found in different amounts in all investigated accessions. The populations were very variable at the molecular level, and the analysis of relationships based on AFLP data, showed that similarity based on Jaccard’s index ranged between 0.330 and 0.742. Our investigations allowed us to identify a population that may be considered as a good source of GLA. 相似文献
1000.
Saeid Amiri Mohammad Jafari Jozani Reza Modarres 《Journal of Agricultural, Biological & Environmental Statistics》2014,19(1):1-17
Ranked set sampling is a sampling approach that could lead to improved statistical inference when the actual measurement of the variable of interest is difficult or expensive to obtain but sampling units can be easily ordered by some means without actual quantification. In this paper, we consider the problem of bootstrapping an unbalanced ranked set sample (URSS) where the number of observations from each artificially created stratum can be unequal. We discuss resampling a URSS through transforming it into a balanced RSS and extending the existing algorithms. We propose two methods that are designed to obtain resamples from the given URSS. Algorithms are provided and several properties, including asymptotic normality of estimates, are discussed. The proposed methods are compared with the parametric bootstrap using Monte Carlo simulations for the problem of testing a hypothesis about the population mean. 相似文献