Since the discovery of elevated concentrations of selenium in the water, sediments, and biota at the Kesterson Wildlife Refuge, several studies regarding trace element distribution in the San Joaquin Valley and their potential environmental impacts have been initialed. We conducted a reconnaissance investigation to assess the concentration of boron, selenium, arsenic, molybdenum, uranium and vanadium using inductively coupled mass spectroscopy in prominent vegetation in the San Joaquin Valley. Five regions representing a range of geochemical environments with known differences in trace element concentrations in their soils or shallow ground water were selected for plant and soil sampling. Concentrations of boron, selenium arsenic, molybdenum, uranium, and vanadium in soil and tissue will be presented for these geographic areas for alfalfa, almonds, cotton, garlic, grapes, onions, tomatoes, and wheat. Interpretations of the wide range of trace element tissue concentrations that have been found will be discussed.
S.R. Grattan, R.O. Miller, and J.P. Mitchell
Maria J. Berenguer, Paul M. Vossen, Stephen R. Grattan, Joseph H. Connell, and Vito S. Polito
A comparative study was conducted to evaluate the influence of seven different levels of irrigation applied to `Arbequina I-18' olive (Olea europaea L.) trees grown in a super-high-density orchard (1,656 trees/ha) in the Sacramento Valley of California. Water was applied differentially by drip irrigation at rates of 15%, 25%, 40%, 57%, 71%, 89%, and 107% evapotranspiration (ETc) in 2002, and 28%, 33%, 55%, 74%, 93%, 117%, and 140% ETc in 2003. Each treatment was replicated three times. Olives were harvested on two different dates each year from each of 21 plots. Three of four harvest dates showed a decrease in maturity index with increasing irrigation levels. Oils were made from olive samples collected from each plot and analyzed for oil quality parameters. Total polyphenol levels and oxidative stability decreased as the trees received more water, especially for the three lowest irrigation treatment levels in 2002, but few differences were noted between treatments in 2003 when all the trees were irrigated more heavily. Average oxidative stability was correlated very closely with total polyphenol content with r 2 = 0.98 in 2002 and 0.94 in 2003. In 2002, free fatty acid levels increased and peroxide levels were unchanged, but in 2003, free fatty acid levels were unchanged and peroxide levels decreased in treatments receiving more water. Saturated fatty acids did not significantly change in 2002, due to tree irrigation level. The mono-unsaturated fatty acid levels and oleic–linoleic relationship declined while poly-unsaturated fatty acid levels increased in 2002 with increased irrigation. In 2003, there was no notable difference in the ratio of mono to poly unsaturated fatty acid levels. The individual fatty acid most consistently affected by more irrigation water was stearic, which decreased in both years. Total sterol content (mg·kg–1), percentages of cholesterol and erythrodiol were significantly influenced by tree irrigation levels, but increased in one year and either decreased or were unchanged the next. Oil sensory properties of fruitiness, bitterness, and pungency all declined in oils made from trees receiving more water. The lowest irrigation levels produced oils that were characterized by excessive bitterness, very high pungency, and woody, herbaceous flavors. Intermediate irrigation levels (33% to 40% ETc) produced oils with balance, complexity, and characteristic artichoke, grass, green apple, and some ripe fruit flavors. Higher irrigation levels lowered oil extractability and produced relatively bland oils with significantly less fruitiness and almost no bitterness or pungency.
J.P. Mitchell, C. Shennan, S.R. Grattan, and D.M. May
Effects of deficit irrigation and irrigation with saline drainage water on processing tomato (Lycopersicon esculentum Mill, cv. UC82B) yields, fruit quality, and fruit tissue constituents were investigated in two field experiments. Deficit irrigation reduced fruit water accumulation and fresh fruit yield, but increased fruit soluble solids levels and' led to higher concentrations of hexoses, citric acid, and potassium. Irrigation with saline water had no effect on total fresh fruit yield or hexose concentration, but slightly reduced fruit water content, which contributed to increased inorganic ion concentrations. Fruit set and marketable soluble solids (marketable red fruit yield × percent soluble solids) were generally unaffected by either irrigation practice. Water deficit and salinity increased starch concentration during early fruit development, but, at maturity, concentrations were reduced to < 1%, regardless of treatment. Higher fruit acid concentrations resulted from water deficit irrigation and from irrigation with saline water relative to the control in one year out of two. These results support the contention that deficit irrigation and irrigation with saline drainage water may be feasible crop water management options for producing high quality field-grown processing tomatoes without major yield reductions. Appropriate long-term strategies are needed to deal with the potential hazards of periodic increases in soil salinity associated with use of saline drainage water for irrigation.
C. M. Grieve, J.A. Poss, S.R. Grattan, P.J. Shouse, J.H. Lieth, and L. Zeng
To explore the possibility that saline wastewaters may be used to grow commercially acceptable floriculture crops, a study was initiated to determine the effects of salinity on two statice cultivars. Limonium perezii (Stapf) F. T. Hubb. `Blue Seas' and L. sinuatum (L.) Mill `American Beauty' were grown in greenhouse sand cultures irrigated with waters prepared to simulate saline drainage waters typically present in the western San Joaquin Valley (SJV) of California. Seven salinity treatments were imposed on 3-week-old seedlings. Electrical conductivities of the irrigation waters (EC) were 2.5 (control), 7, 11, 15, 20, 25, and 30 dS·m–1. Vegetative shoots were sampled for biomass production and ion analysis ten weeks after application of stress. Flower stem numbers, length, and weight were determined at harvest. Stem length of L. perezii was significantly reduced when irrigation water salinity exceeded a threshold of 2.5 dS·m–1. Salt tolerance threshold based on stem length for L. sinuatum was 7 dS m-1. The species exhibited significant differences in shoot-ion relations which appear to be related to differences in salt tolerance. Sodium, K+, Mg2+, and total-P were more strongly accumulated in the leaves of L. sinuatum than L. perezii. Both species accumulated K+ in preference to Na+, but selectivity for K+ over Na+ was significantly higher in L. sinuatum than in the more salt-sensitive L. perezii. Chloride concentration in L. sinuatum leaves increased significantly as salinity increased, whereas the 20-fold increase in substrate-Cl had no effect on leaf-Cl in L. perezii. Both Limonium species completed their life cycles at salt concentrations exceeding 30 dS·m–1, a character associated with halophytic plants. Maximum growth of each species, however, occurred under relatively low salt stress, and steadily declined as external salinity increased. Based on this crop productivity response, L. perezii should be rated as sensitive and L sinuatum as moderately tolerant.
L. Ferguson, J.A. Poss, S.R. Grattan, C.M. Grieve, D. Wang, C. Wilson, T.J. Donovan, and C.-T. Chao
Performance of `Kerman' pistachio (Pistacia vera L.) trees on three rootstocks (P. atlantica Desf., P. integerrima Stewart and `UCB-1', a P. atlantica × P. integerrima hybrid) was evaluated with 2-year-old trees grown in sand-tank lysimeters under combined SO4 2- and Cl- salinity and boron (B) stress for 6 months. Four salinity treatments were imposed by irrigating the plants with water at electrical conductivity (ECiw) of 3.5, 8.7,12, or 16 dS·m-1 each containing B at 10 mg·L-1. Growth of `Kerman' was evaluated based on increase in total leaf area, increase in trunk diameter, and total above-ground biomass production. All growth parameters decreased as salinity increased, but were not significant until ECiw exceeded 12 dS·m-1. However, growth of `Kerman' on P. atlantica and `UCB-1' was considerably better than on P. integerrima at 16 dS·m-1. The onset and severity of foliar injury differed among scions and treatments and was attributed primarily to B toxicity, rather than the effects of salinity. Concentrations of B in injured leaf tissue ranged from 1000 to 2500 mg·kg-1. Leaf injury decreased with increasing salinity, although leaf B was not significantly reduced suggesting an internal synergistic interaction between B and other mineral nutrients. However for P. vera on P. integerrima, the highest level of salinity produced the greatest injury, possibly as a combination of B plus Cl- and/or Na+ toxicity. Leaf transpiration, stomatal conductance, and chlorophyll concentration of P. vera, determined by steady-state porometry, were also reduced to a greater degree by combined salinity and B when budded on P. integerrima than on the other two rootstocks.