In 1998, Monterey County Water Recycling Projects began delivering water to 12,000 acres in the northern Salinas Valley. Two years later, an ongoing study began assessing the effects of the recycled water on soil salinity. Eight sites are receiving recycled water and a control site is receiving only well water. In data collected from 2000 to 2012, soil salinity of the 36-inch-deep profile was on average approximately double that of the applied water, suggesting significant leaching from applied water (irrigation) or rainfall. In this study, we investigated some of the soil water hydrology factors possibly controlling the soil salinity results. Using soil water balance modeling, we found that rainfall had more effect on soil salinity than did leaching from irrigation. Increasing applied water usually only correlated significantly with soil salinity parameters in the shallow soil profile (1 to 12 inches depth) and at 24 to 36 inches at sites receiving fairly undiluted recycled water. Winter rains, though, had a critical effect. Increasing rainfall depths were significantly correlated with decreasing soil salinity of the shallow soil at all test sites, though this effect also diminished with increased soil depth. When applied water had high salinity levels, winter rainfall in this area was inadequate to prevent soil salinity from increasing. U sing recycled wastewater for agriculture and landscaping has environmental benefits because it limits the wastewater discharge into natural waterways while helping to preserve the supply of potable water for human consumption. Recycled water (tertiary-treated wastewater) has been used by a majority of growers in the Monterey County Water Recycling Projects (MCWRP) Salinas Valley area since 1998. An ongoing study, initiated in 2000, is comparing the changes in soil salinity between a field that has received only well water and eight field sites in the MCWRP area that have received recycled water since 1998. Each test site uses a specific blend of recycled water (the fraction ranges from 40% to 90%) and well water for irrigation, allowing assessment of the relative impacts of the water quality on soil salinity parameters.Recently, a feasibility study of the use of recycled water for vineyard irrigation in the Carneros and MillikenSarco-Tulocay (MST) regions near Napa indicated that leaching by winter rains averaging more than 20 inches a year was sufficient to maintain soil salinity, sodium (Na) and chloride (Cl) levels within acceptable ranges for grape production (Weber et al. 2014; page 59, this issue). Winter rainfall is about 13 inches a year in the MCWRP area, and our goal in this study was to ascertain the effectiveness of irrigation leaching compared with rainfall leaching.Overall, the average soil salinity parameters -electrical conductivity (EC e ), Na, Cl and sodium adsorption ratio (SAR) -at the test sites were highly correlated with the average recycled water quality values, as we describe in our other article on this study (Platts and Grismer 2014; page 68, this i...

Three races of Fusarium oxysporum f.sp. lactucae, cause of fusarium wilt of lettuce, are known in Japan, where the pathogen was first observed in 1955. Fusarium wilt first affected commercial U.S. lettuce production in 1990 in Huron, Calif., but did not become a serious problem in the U.S. until 2001 when it reappeared in Huron and appeared in the Yuma, Arizona lettuce production area. Reactions of three fusarium wilt differentials (`Patriot', susceptible to races 1, 2 and 3; `Costa Rica No. 4', resistant to race 1, and susceptible to races 2 and 3; and `Banchu Red Fire', susceptible to races 1 and 3, and resistant to race 2) in a naturally-infected commercial field test and artificially-inoculated greenhouse tests, indicated presence of race 1 in the Yuma lettuce production area. Reactions of these differentials to an isolate from Huron confirmed the presence of race 1 in that area. Consistent with previous results from the U.S. and Japan, `Salinas' and `Salinas 88' were resistant to the Yuma and Huron isolates of race 1, whereas `Vanguard' was highly susceptible. Limited F1 and F2 data indicate that resistance to race 1 in `Costa Rica No. 4' and `Salinas' is recessive. `Calmar' is the likely source of resistance in `Salinas' and `Salinas 88'.

The use of recycled water for agriculture is a long-term water strategy in California. A study in the 1980s in Monterey County showed recycled water increased soil salinity but not to a level unacceptable for agriculture. Most growers in the northern Salinas Valley have been using it since 1998, and yet providers of the water and many growers are concerned that the sustained use of recycled water might cause deterioration of the soil. An ongoing study, initiated in 2000, compares the changes in soil salinity between a field receiving only well water and eight fields that receive recycled water. In 13 years of data, the average soil salinity parameters at each site were highly correlated with the average water quality values of the recycled water. Soil salinity did increase, though not deleteriously. Of most concern was the accumulation of chloride at four of the sites, to levels above the critical threshold values for chloride-sensitive crops.

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