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Many research papers on crop water requirements of vegetables have been produced since the publication of the FAO56 guidelines in 1998. A review of this literature has shown that determination of crop evapotranspiration (ET c ) using the K c -ET o approach, i.e., the product of the specific crop coefficient (K c ) by the reference evapotranspiration (ET o ), is the most widely-used method for irrigation water management. Consequently, a review was made to provide updated information on the K c values for these crops. The reviewed research provided various approaches to determine K c in its single and dual versions. With this purpose, actual crop ET (ET c act ) was determined with lysimeters, or by performing the soil water balance using measured soil water content and computational models, or by using Bowen ratio energy balance and eddy covariance measurements, or by using remote sensing applications. When determining the basal K c (K cb ), the partitioning of ET c act was evaluated using different approaches, though mainly using the FAO56 dual K c method. Since the accuracy of experimentally-determined K c and K cb values depends upon the procedure used to compute ET o , as well as accuracy in determining and partitioning of ET c act , the adequacy of the measurement requirements for each approach was carefully reviewed. The article discusses in detail the conceptual methodology relative to crop coefficients and the requirements for transferability, namely distinguishing between actual and standard K c and the need to appropriately use the FAO segmented K c curve. Hence, the research papers selected to update and consolidate mid-season and end-season standard K c and K cb were those that computed ET o with the FAO56 PM-ET o equation; and that also used accurate approaches to determine and partition ET c act for pristine, non-stressed cropping conditions. Under these experimental conditions, the reported K c and K cb values relative to the mid-and end-season could be considered as transferable standard K c and/or K cb values after adjustment to the standard climate adopted in FAO56, where average RH min = 45% and average u 2 = 2 m s −1 over the mid-season and late season growth stages. For each vegetable crop, these standard values were then compared with the FAO56 tabulated K c and K cb values to define the updated values tabulated in the current article. In addition, reported ancillary data, such as maximum root zone depth, maximum crop height, and soil water depletion fraction for no water stress, were also collected from selected papers and tabulated in comparison with those given for the crops in FAO56. The presentation of updated crop coefficient results is performed by grouping the vegetables differently than in FAO56, where distinction is made according to their edible parts:(1) roots, tubers, bulbs and stem vegetables; (2) leaves and flowers vegetables; (3) fruit and pod vegetables; and (4) herbs, spices and special crops, with most of them being newly introduced herein. The updated K c and K cb of veget...

Molecular characterisation and phenetic similarities between several cultivars of P. communis and P. pyrifolia, and genotypes of P. cordata, P. bourgaeana and P. pyraster were investigated through RAPD markers. Sixty decamer primers were screened, generating polymorphic patterns of Occidental and Oriental pear genotypes. Twenty-two selected primers originated clear and reproducible patterns, produced a total of 358 bands, 327 of them polymorphic. For 10 of the 12 genotypes analysed it was possible to find genotype-specific RAPDs and fragment patterns which could be used for cultivar identification. The patterns distinguished between genotypes and their analysis established a first approach to phenetic classification within the Pyrus genus based on DNA markers, clustering the genotypes according to their geographic origin. RAPD analysis of in vitro and in vivo material of seven cultivars was also performed, resulting in identical patterns for each genotype. #

The A&P approach, developed by Allen and Pereira (2009), estimates single and basal crop coefficients (K c and K cb ) from the observed fraction of ground cover (f c ) and crop height (h). The practical application of the A&P for several crops was reviewed and tested in a companion paper (Pereira et al., 2020). The current study further addresses the derivation of optimal values for A&P parameter values representing canopy transparency (M L ) and stomatal adjustment (F r ), and tests the resulting model performance. Values reported in literature of M L and F r were analysed. Optimal M L and F r values were derived by a numerical search that minimized the differences between K cb A&P with standard K cb for vegetable, field, and fruit crops as tabulated by Pereira et al. (2021aPereira et al. ( , 2021b and Rallo et al. (2021). Sources for f c were literature reviews supplemented by a remote sensing survey. Computed K cb and K c for mid-and end-season together with associated parameters values were tabulated. To improve the usability of the M L and F r parameters a cross validation was performed, which consisted of the linear regression between K cb computed by A&P and observed K cb relative to independent data sets obtained from field observations. Results show that both series of K cb match well, with regression coefficients very close to 1.0, coefficients of determination near 1.0, and root mean square errors (RMSE) of 0.06 for the annual crops and RMSE = 0.07 for the trees and vines. These errors represent less than 10% of most of the computed tabulated K cb. The tabulated F r and M L of this paper can be regarded as defaults to support A&P field practice when observations of f c and h are performed. Therefore, the A&P approach shows to be appropriate for use in irrigation scheduling and planning when f c and h are observed using ground and/or remote sensing, hence supporting irrigation water savings.

Abstract:Agriculture is considered one of the main nitrogen (N) pollution sources through the diffuse emissions of ammonia (NH 3 ) and nitrous oxide (N 2 O) to the atmosphere and nitrate (NO 3 − ) to water bodies. The risk is particularly high in horticultural production systems (HPS), where the use of water and fertilizers is intensive and concentrated in space and time, and more specifically, in the case of vegetable crops that have high growth rates, demanding an abundant supply of water and nitrogen forms. Therefore, to comply with the EU environmental policies aimed at reducing diffuse pollution in agriculture, there is the need for mitigation practices or strategies acting at different levels such as the source, the timing and the transport of N. HPS are often well suited for improvement practices, but efficient and specific tools capable of describing and quantifying N losses for these particular production systems are required. The most common mitigation strategies found in the literature relate to crop, irrigation and fertilization management. Nevertheless, only the success of a mitigation strategy under specific conditions will allow its implementation to be increasingly targeted and more cost effective. Assessment methods are therefore required to evaluate and to quantify the impact of mitigation strategies in HPS and to select the most promising ones.