Analysis of Trace Volatile Compounds Emitted from Flat Ground and Formed Bed Anaerobic Soil Disinfestation in Strawberry Field Trials on California’s Central Coast

Anaerobic soil disinfestation (ASD) is emerging globally as an alternative to fumigant pesticides. To investigate ASD mechanisms, we monitored microbially produced volatile organic compounds (VOCs) and other volatile gases in situ using Fourier Transform Infrared Spectroscopy. Study plots infested with Fusarium oxysporum, Macrophomina phaseolina, and/or Verticillium dahliae included: organic flat ground (fASD, 6.7 + 13.5 megagrams per hectare, Mg/ha, rice bran/broccoli) and uncovered soil treated with mustard seed meal (MSM, 3.4 Mg/ha) at one site performed in fall of 2018; formed bed (bASD, 20 Mg/harice bran), control (UTC) and fumigant (FUM) at a second field site in fall of 2019 and 2021. Here, we present VOC diversity and temporal distribution. fASD generated 39 VOCs and GHGS, including known pathogen suppressors: dimethyl sulfide, dimethyl disulfide, and n-butylamine. bASD produced 17 VOCs and greenhouses gases (GHGs), 12 of which were also detected in fASD but in greater concentrations. Plant mortality and wilt score (fASD: 3.75% ± 4.79%, 2.8 ± 0.8; MSM: 6.25% ± 12.50%, 2.7 ± 0.3; bASD: 61.27% ± 11.26%, 4.1 ± 0.5; FUM: 13.89% ± 7.17%, 2.3 ± 0.2; UTC: 76.63% ± 25.11%, 4.3 ± 1.0) were significantly lower for fASD and MSM versus bASD and UTC (p \u3c 0.05). Only FUM was not statistically different from fASD and MSM, and was significantly lower than UTC and bASD (bASD-FUM, p \u3c 0.05; UTC-FUM, p \u3c 0.05). The cumulative strawberry yield from bASD-treated plots was not different from FUM or UTC (bASD: 60.3 ± 13.6; FUM: 79.4 ± 9.19; UTC: 42.9 ± 12.4 Mg/ha). FUM yield was significantly greater than UTC (p = 0.005). These results, and to a far greater extent, additional challenges faced during both bASD trials, suggest that bASD is not as effective or as feasible at maintaining overall plant health as fASD or traditional fumigants. However, differences in management practices and environmental conditions at both sites across years cannot be fully excluded from consideration and many of our observations remain qualitative in nature

A Cropping Systems Approach to Improving Water Use Efficiency in Semi-Arid Irrigated Production Areas

This recently-completed 3-year field study evaluated the effectiveness of winter cover crop incorporation and surface gypsum applications relative to conventional fallows for maintaining/improving soil physical properties, stand establishment and crop productivity in a cropping system relying on saline drainage water for irrigation. Six amendment/soil cover treatments were imposed on a rotation of tomato-tomato-cotton as summer crops. Drainage water accounted for about 70% of the total water applied over the course of the experiment. Yields of toamtoes irrigated with saline water were maintained relative to non-saline irrigation in year 1, but were decreased by 33% in year 2. Estimated cotton lint yields of plants irrigated with saline drainage water in 1994, following two seasons of drainage water irrigation, were similar to yields of plants irrigated exclusively with non-saline water. Soil surface crust strength, measured by micro penetrometer was lower in gypsum and cover-crop amended plots relative to saline water irrigated fallow plots during the period of cotton seedling emergence in 1994 in the third year of the experiment. Water stable aggregation was increased following cover crop incorporation relative to saline fallows. Following two seasons of saline drainage water reuse, emergence of cotton seedlings was highest in gypsum-amended plots, but considerably lower in cover crop incorporated plots. Mechanisms accounting for poor establishment following cover crop incorporation may include higher incidences of seed and seedling pathogens in plots where cover crop residues had been incorporated into the soil, and stubble-reinforced surface crusts that resulted in interconnected slabs that impeded timely seedling emergence. These findings and increasing soil surface ECe and SAR values during the course of this study point to the need for special management practices for sustained crop production if drainage water is routinely used

Can Hedgerows Attract Beneficial Insects and Improve Pest Control? A Study of Hedgerows on Central Coast Farms

The objectives of this study, conducted from 2005 to 2007, were (1) to assess the habitat quality of different hedgerow plants for insect natural enemies and pests, (2) to track the movement of insects from hedgerows into adjacent crop fields and (3) to test the effect of hedgerows on parasitism rates of an economically important pest, the cabbage looper (Trichoplusia ni). This study took place at four farms with hedgerows on the Central Coast of California