Plant growth promoting rhizobacteria (PGPR) are able to provide cross-protection against multiple stress factors and facilitate growth of their plant symbionts in many ways. The aim of this study was to isolate and characterize rhizobacterial strains under natural conditions, associated with naturally occurring representatives of wild plant species and a local tomato cultivar, growing in differently stressed Mediterranean ecosystems. A total of 85 morphologically different rhizospheric strains were isolated; twenty-five exhibited multiple in vitro PGP-associated traits, including phosphate solubilization, indole-3-acetic acid production, and 1-aminocyclopropane-1-carboxylate deaminase activity. Whole genome analysis was applied to eight selected strains for their PGP potential and assigned seven strains to Gammaproteobacteria, and one to Bacteroidetes. The genomes harboured numerous genes involved in plant growth promotion and stress regulation. They also support the notion that the presence of gene clusters with potential PGP functions is affirmative but not necessary for a strain to promote plant growth under abiotic stress conditions. The selected strains were further tested for their ability to stimulate growth under stress. This initial screening led to the identification of some strains as potential PGPR for increasing crop production in a sustainable manner.

The effects of liquid dairy cattle (Bos taurus) manure on corn (Zea mays L.) yield and composition were studied in a 4-yr field experiment conducted under a Mediterranean environment. In addition, long-term impact of (8-yr) manure application on soil-available NO 3 -N, P, and K; organic C; Kjeldahl N; and salinity was investigated. Four treatments were established in plots, previously used for a similar 4-yr experiment with winter wheat (Triticum aestivum L.). Treatments were: (i) application of 80 Mg manure ha 21 yr 21 ; (ii) single application of the equivalent N-P as inorganic fertilization (260 kg N ha 21 yr 21 and 57 kg P ha 21 yr 21 ); (iii) identical to (ii), but with split N application; and (iv) no fertilization. Corn grain and silage yields, N-P-K plant concentration, and uptake were significantly increased by manure or inorganic fertilizer addition relative to the control. During the 4-yr corn experiment, the amounts of available NO 3 -N in the soil profile of manure plots were higher than control, but similar to both inorganic fertilization treatments. Manure application maintained the amounts of soil available NO 3 -N, P, and K at desirable levels, almost each year of the total 8-yr application. However, soil organic C and Kjeldahl N remained unchanged. At the end of the experiment, soil salinity below 30 cm was significantly increased on manure or inorganic fertilizer addition relative to the control, but at levels acceptable for most crops. In conclusion, soil application of liquid dairy cattle manure at a rate equivalent to the recommended inorganic fertilization can enhance corn yield and composition and maintain soil fertility at desirable levels, without increasing soil salinity at unacceptable levels.

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ciency was attributed to reduced NH 3 volatilization (Beauchamp, 1983). Liquid cattle (Bos taurus) manure should be applied to soils in Manure application rates to soil depend on many such a manner that would improve soil fertility and crop production factors, including the crop, amount of manure available, without causing salinity problems or increasing NO Ϫ 3 levels. This study investigated the influence of liquid cattle manure on winter wheat manure composition, amount of land available for (Triticum aestivum L. cv. Yecora) germination, growth, and nutrient spreading, quantity of soil available nutrients, and the utilization. Four treatments were applied in the same plots in a 4-yr fraction of manure nutrients that could become availfield experiment with winter wheat: (i) application of 40 Mg ha Ϫ1 yr Ϫ1 able. Heavy application rates can have adverse effects liquid dairy cattle manure (wet weight basis) before sowing; (ii) single on soils and plants (Chang et al., 1991). Excessive loadapplication of 120 and 26 kg ha Ϫ1 yr Ϫ1 N and P, respectively, as ings of cattle manure (liquid or solid) may increase soil inorganic fertilizers before sowing; (iii) as in ii, but with split applicasalinization and NO Ϫ 3 contamination of ground waters tion of N, half the amount before sowing and the rest at tillering; and (Lund et al., 1975; Evans et al., 1977). To avoid adverse (iv) no fertilization. The biological evaluators used to compare the effect of the treatments were (i) number of seedlings per square meter effects of manure on the environment, manure should at tillering for the first year only and (ii) dry biomass at heading and be managed with caution. The objectives of this study harvest; plant concentration and uptake of N, P, and K; and grain were to investigate the effects of liquid dairy cattle mayield for every year of experimentation. The results showed that nure on winter wheat (Yecora) and soil salinity and ferapplication of manure did not affect seed germination but resulted tility. in a significant increase in dry biomass at the two growth stages and in grain yield and nutrient uptake, similar to the inorganic N and P fertilization. The amounts of soil available NO 3 ϪN and P were MATERIALS AND METHODS significantly increased while at the end of the field experiment, soil salinity, organic C, and total N levels remained unchanged.

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