Lettuce

Response of Small-Seeded Vegetables to Several Anticrustants

Poor stand establishment is often a limiting factor in vegetable production in the Willamette Valley. Carrots, onions, and lettuce, in particular, often fail to emerge because of soil crusting. Most small-seeded crops lack the vigor necessary to emerge when resisted by significant soil impedance. A high degree of impedance or crusting (also known as soil mechanical resistance) is caused by breakdown of soil particle aggregates. Several treatments exist which may reduce the breakdown of aggregates.

Effect of Soil pH and Nitrogen Fertilizers on Stand Establishment of Small-Seeded Vegetables

Vegetable yields are, within limits, proportional to the initial stand establishment of the crop, i.e. the percentage of seed which successfully germinates, emerges, and commences sunlight-dependent growth. Improvements in stands should increase yields, reduce thinning labor, and may reduce variability in produce size and maturity at harvest. The purpose of this experiment was to determine the effects of soil pH and type (neutral, basic, acid-forming) of N fertilizer on stand establishment of several small-seeded vegetables.

Soil Acidity an Important Factor in Production of Beans, Lettuce, Carrots

These experiments in 1979 were a continuation of a series begun in the 1977 growing season and repeated in 1978. Bush beans, lettuce, and carrots were again the crops used to determine the effects of soil pH and N fertility level on vegetable yield. In 1979, new plots were established with lime rates of 0, 2, 4, and 6 tons/acre. This produced a narrower range of pH (5.0 to 5.8) than was present in the 1977 and 1978 experiments (4.9 to 6.6).

Methods

Lettuce Yields Affected by Transplanting and Direct Seeding

Lettuce is difficult to plant to stand, particularly in early spring and again during mid-summer periods of high soil temperature. Transplanting greenhouse-grown seedlings may offer the advantage of nearly ideal stands and even permit one extra crop during the growing season. Other possible advantages which may offset the cost of raising transplants include elimination of thinning equipment or labor, reduced herbicide use or cultivation, and production of a more uniform head of lettuce.

Methods

Effects of Soil Acidity and N Fertilizers on Vegetable Stands

Previous experiments at the North Willamette Station (1979, 1980) have established that stands of carrot, cauliflower, and lettuce on Willamette silt loam are inhibited at pH less than 5.8 compared to higher pH. In addition, broadcast applications of N fertilizers have reduced stands when compared with unfertilized soil. In the 1979 experiments, ammonium sulfate at 112 kg N/ha depressed stands by approximately 15% to 45%, depending on the crop; at 224 kg N/ha, ammonium sulfate depressed stands by 30% to 55%.

Size Grading of Transplants on Lettuce Head Size Variability (1984)

Transplanting lettuce seedlings can insure a nearly perfect stand. In addition, transplanting offers the possibility of bringing the crop to market earlier than a direct-seeded crop, taking advantage of higher early season market prices and allowing marketing over a longer time period. Perhaps more importantly, transplanting may allow for multiple cropping. In the Willamette Valley, for example, transplanting would allow three rather than two crops of lettuce. Transplanting may also take place when soil conditions would not allow direct seeding.