FAO/UNDP MEX 74/003 / Technical Report / Prepared for the International Conference on Managing Saline Water for Irrigation, Lubbock, Texas, U.S.A. August 16-20, 1976. / FAO of United Nations Project, UAAAN/FC / Buenavista, Saltillo, Coahuila, 1976. / Note: Item states For Internal Use only. Online copy not available. / INTRODUCTION: More than 52% cultivable area of Mexico is classified as arid and semi-arid. Nearly half of this area, particularly in the Northern States is extremely arid and presents with some salinity, alkalinity and water logging problems. Ground water, when available for irrigation, is often saline or moderately saline-sodic. The soils of this region are calcareous and contain some salts and sodium. Soils also contain sub-surface horizon rich in carbonate and compact in nature, which may be 30-90 cms below the ground surface. Before planning a major irrigation system for crop production, provision of drainage and leaching of salts is often recommended for this region. The good quality water from underground source may rarely be available for leaching salts and when available pumping costs are prohibitively expensive. It has also been pointed out in the past that such lands could be used to harvest water. In fact, rudimentary water harvesting systems have been established by local people in some parts of this area. Thus, with the need for integral land use and water reclamation in mind, a multipurpose water use and water harvesting system was developed. The requirements of this system, among others, are: (1) To collect enough water for multiple use inside or outside the system, (2) To increase the desired production of the marginal saline land within the system, and, (3) To provide an economically feasible long term farming system for the low-income community. Such system is under development at the Ejido San Francisco del Barrial, near Parras in the State of Coahuila.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

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The response of in vitro-grown Solanum tuberosum L., cvs. Russet Burbank (RB) (salt-sensitive) and Sierra (S) (salt-tolerant) potatoes was investigated when [NaCl] was increased from 0 to 80 mM in the presence of 6, 20, and 30 mM [K] in a Murashige and Skoog (MS) basal medium. The tested growth parameters, Mg and Ca content, and K+/Na + ratios in the laminae and the roots were negatively affected as [NaCl] increased. The salt stress was relatively severe on growth of RB plants whereas the salt-tolerant (S) variety was affected to a lesser extent. There were indications that Na in the plant may promote Na translocation. In both cultivars, 22Na was not distributed equally in all plant parts; the lower lamina accumulated the highest amount (216 and 183 DPM mg -1 FW) followed by stem (197 and 182), petioles (187 and 168), and the upper lamina (149 and 121) for RB and S, respectively. / The salt resistance of S is associated not only with a superior capacity to accumulate high Na+ in the roots for osmotic adjustment, but also with resistance to Na movement to the shoot. / The effect of [K] on plant growth showed two main characteristics. In non-saline media, increasing [K] enhanced growth of S, while RB showed optimum growth when the normal (20 mM) level was present in the MS medium. In saline media, elevating [K] alleviated the growth reduction of RB at low salinity, and S at both low and high salinity. This ameliorative effect of K may be attributed to the suppression of both Na+ uptake, and Na + translocation in the plant.

Water management for the irrigation of containerized production remains a task reserved to a highly qualified personnel. Without proper instruments to determine the actual water needs, nursery crops can face growth losses of 20 to 30%. / Reviewing the different methods that are used in field production, tensiometer have shown the greatest potential of adaptation to potted plants. / Tests on the utilization of tensiometer were realized on two peat-vermiculite substrates, using two types of porous cup (1 bat--standard flow and 1 bar--high flow). The instruments were tested while permanently fixed in the growing medium, and temporarily fixed for three hours in the growing medium. / The results show that the instruments give excellent measurements for normal condition of growth, requiring saturation level between 50 and 100%, and that for both mode of operation. / Preferably, the choice of the instrument should be based on the hydraulic characteristics of the substrate. Little difference has been found using both instrument in the substrate 1, but in substrate 2 however, the high flow porous cups have given better response. The high flow cups have higher porosity and bigger pores that suit better substrate 2, which is made of coarser particles.

In a field trial during 1995/96, epidemics of <I>Pyrenophora teres</I> and <I>Rhynchosporium secalis</I> were studied in winter barley with concurrent records of weather data to identify key environmental parameters that affect epidemics. Temperature was identified as a key influence in the onset of <I>P. teres</I> epidemics. Disease symptoms were observed to progress when daytime temperatures consistently reached 10°C and minimum nightime temperatures for the same period remained above 5°C. Short leaf wetness periods and longer photoperiods also correlated with increased disease levels during the <I>P. teres </I>epidemic. In <I>R. secalis,</I> relationships between disease onset and individual environmental parameters were not consistent, however, high rainfall events and prolonged leaf wetness periods were recorded prior to greatest disease increase. Hypotheses based on individual and combined weather criteria, based on the results of the 1995/96 field trials, were tested in controlled conditions. The effect of temperature on <I>P. teres</I> was confirmed, with small differences between ascospores and conidiospores. Latent period of both <I>P. teres</I> and <I>R. secalis</I> was influenced by cultivar resistance, inoculum concentration and plant growth stage. In a second field trial in 1996/97 reduced dose fungicide programmes, using hypotheses of epidemic development based on environmental criteria, were tested and compared favourably to a standard programme with greater fungicide doses. Environmental criteria were combined within a decision model for timed reduced-dose fungicide programmes for each pathogen, where risk scores were allotted for each set of criteria and fungicide treatment decision was based on the cumulative risk score. Both the <I>P. teres</I> and <I>R. secalis</I> decision models were tested in a final field trial in 1997/98. Lower disease levels and greater yield response, with lower fungicide input, was achieved from both models compared to a standard fungicide programme. The potential for using the <I>P. teres</I> and <I>R. secalis</I> decision models in a decision support system for cereals is discussed.

Grazing and no-till management in organic systems have been recently proposed tools to improve nutrient cycling and sustainability. From 2008 to 2012 a series of field experiments were established to identify green manure species and green manure management options to maximize N benefit to following cash crops and explore the opportunities to reduce tillage during the green manure phase of an organic rotation. A total of four green manure systems (double-cropped green manures, relay-cropped green manures, full season green manures, and catch crops after grazed full season green manures), three green manure management options (soil incorporation, grazing and no-till), and 10 green manure species, as well as, three green manure mixtures were tested. Double-cropped pea (Pisum sativum cv. 40-10) and relay-cropped red clover (Trifolium pratense) produced around 900 kg ha-1 and 2000 kg ha-1 of biomass respectively. The greatest biomass producing full season green manures were hairy vetch (Vicia villosa L.), pea/oat (Avena sativa cv. Leggett/Pisum sativum cv. 40-10) and sweet clover (Mellilotus officinalis cv. Norgold). Pea/oat and hairy vetch were the most weed competitive species and on average contained less than 15% weed biomass. Among all the systems and managements tested, nitrogen availability was greatest when full season green manures were grazed. On average grazing increased soil NO3-N by 25% compared to soil incorporation using tillage. Among grazed species, pea/oat mix and hairy vetch green manures resulted in the greatest amount of soil available NO3-N. Catch crops after grazing green manures, regardless of the species, significantly reduced N leaching risk compared to no catch crop treatment, but also reduced wheat productivity the following year. Catch crop biomass productivity and N uptake, soil NO3-N, and wheat productivity were similar in direct seeded and conventionally seeded plots. Grazing may be an effective tool in reducing tillage in organic agriculture because of its ability to accelerate the N mineralization from catch crop biomass. This study was the first study to use grazing as a management tool for green manures in organic systems. Results provide strong evidence that green manures, especially when grazed, can be effective nitrogen suppliers in organic grain based rotations.