In spite of potential benefits and positive assessments of reducing primary tillage operations, only a small part of irrigated row crops is currently managed using reduced tillage, for reasons that include concerns about its agronomic suitability for certain crop rotations. Three years of a tomato/corn rotation under standard and no-tillage management were used to understand the fate of a fertilizer and cover crop nitrogen (N) application. Uptake of both inputs was reduced under no-tillage during the year of application, in this case a tomato crop. As a result, more input N was retained in the soil in this system. The initial challenge of reduced tomato yields diminished as no-tillage management remained in place and the soil N reservoir developed. Corn production was not affected by tillage treatment. Inclusion of a legume cover crop increased the amount of fertilizer N retained in the soil over time, more so under no-tillage than under standard tillage, emphasizing the benefit of cover crops in reducing the amount of fertilizer required to maintain productivity. While acceptance of reduced tillage ultimately depends on economic performance, the results of this study support its agronomic viability for irrigated row crops.

No abstract

Onion white rot disease (Sclerotium cepivorum) is a serious production problem throughout the world. Very low pathogen level in the soil can cause significant loss. Generic integrated pest management programs include clean seed, site selection, sanitation, crop rotation, biological and chemical controls, crop resistance to the pest, and other components. Onion white rot disease management currently does not have crop resistance as a component. The lack of resistant germplasm and/or the inability to identify and screen potentially resistant germplasm are primary reasons. Research was conducted to determine if field screening for resistance is feasible, to define field screening methodology, and to identify and/or quantify resistance. Disease incidence was inconsistent from year to year. In some years, disease expression was high; in others, disease was low. Uniform pathogen level and disease expression throughout the experimental field were required for successful screening. Results provide evidence that “resistant” or “tolerant” germplasm does exist, and that disease “resistance”, “tolerance”, or “susceptibility” can vary from slight to strong, suggesting multigenic involvement. “Resistance”/”tolerance” was identified in long-day yellow hybrids and inbreds. `Southport White Globe' selections and derivatives had much higher disease susceptibility than yellow or brown skin lines screened.

A survey of 140 processing tomato fields throughout central California was conducted in 1996–97 to determine whether soil factors affect the occurrence of the tomato (Lycopersicon esculentum Mill.) fruit color disorders “yellow eye” (a halo of yellow tissue around the stem scar) and white core (an abnormal amount of internal white tissue); these disorders render fruit unsuitable for use as peeled or diced product. All fields were planted in `Halley' or `Heinz 8892'. Soil samples (0–30 cm) were analyzed for pH, texture, TKN, bicarbonate extractable P, and ammonium acetate-extractable K, Ca, and Mg. Ripe fruit were rated for the incidence (%) of fruit affected by one or both of the disorders, blended color, and % soluble solids (SS). Soil K (in meq., expressed as a % of base exchange) was negatively correlated with the incidence of the disorders, while soil Mg was positively correlated. Fields with extractable K <2% of base exchange averaged 21% of fruits affected by one or both disorders, compared to only 4% of fruits affected in fields with K >2.5% of base exchange and a Mg/K ratio (meq. basis) <12. Percent SS was weakly correlated with extractable K, but blended color was unrelated to any soil factor. In 1997 field trials, both gypsum application (to displace soil Mg) and K fertilization significantly suppressed the color disorders but did not affect yield, blended color, or % SS.