The 75% N and 30 ppm tryptophan combination best increased lettuce head weight, total yield and leaf area index.

tryptophan · yield · Lactuca sativa (garden lettuce)Results agree

1 paper in the same direction as this claim

1. positive
   The three-factor combination gave the highest total yield of lettuce, 33.904 tons per hectare, versus 16.275 tons per hectare in the distilled-water control.

   The Role of Sulfur, Tryptophan Acid, and Methyl Jasmonate in Vegetative Growth, Quality Indicators, and Total Yield of Lettuce Plants · 2024 · compared with control treatment, where plants were only sprayed with distilled water

   Same direction

application · yield · Lactuca sativa (garden lettuce)Positive and negative results

29 papers in the same direction as this claim · 8 in the opposite direction

1. negative
   Foliar selenium treatment generally decreased lettuce yield.

   Alleviation Effect of Selenium on Manganese Stress of Plants · 2018

   Opposite direction

2. negative
   The 1800 ppm foliar rate can decrease head size and percent salable heads of lettuce.

   Lettuce Seedling and Yield Response to Preplant and Foliar Fertilization during Transplant Production1 · 1981

   Opposite direction

3. no effect
   Foliar silicon did not change yielding, leaf number or most leaf element concentrations.

   The response of hydroponically grown lettuce under Mn stress to differentiated application of silica sol · 2015

   Opposite direction

4. no effect
   Automated thinning with the tested spray solutions did not significantly affect lettuce yield.

   Automated Machine for Thinning Lettuce - Development and Evaluation · 2012

   Opposite direction

5. no effect
   Foliar sprays of seaweed, fish and fertilizer products did not affect plant nutrient levels or yields in sweet peppers, broccoli or lettuce.

   The Use of Marine Derived Products and Soybean Meal as Fertilizers in Organic Vegetable Production · 2004 · compared with water control

   Opposite direction

6. no effect
   Air injection did not affect commercial yield.

   Effect of irrigation with injection of air in soil moisture, nitrate availability, electrical conductivity and lettuce productivity grown in plastic greenhouse. · 2010

   Opposite direction

7. no effect
   High foliar selenium and zinc concentrations had no negative growth or yield effect.

   Effects of Foliar Application of Selenium and Combination with Zinc on Selenium Content in Edible Parts of Lettuce Grown in Mineral Soil · 2026

   Opposite direction

8. no effect
   SER leaf spray left shoot head diameter unaffected.

   Silk sericin as a biostimulant for lettuce (Lactuca sativa L.): Effects of foliar spray and soil drenching under water stress · 2026

   Opposite direction

29 papers more in this group

nitrogen · yield · Lactuca sativa (garden lettuce)Positive and negative results

60 papers in the same direction as this claim · 17 in the opposite direction · 1 reporting no difference from an alternative

1. no effect
   Light-dependent nitrate deprivation generally did not reduce lettuce yield, except under strong nitrate reduction.

   The Effect of Light-dependent Application of Nitrate on the Growth of Aeroponically Grown Lettuce (Lactuca sativa L.) · 2004

   Opposite direction

2. negative
   The lower nutrient nitrate level reduced lettuce dry mass yield.

   Nitrate concentration in lettuce leaves depending on photosynthetic photon flux and nitrate concentration in the nutrient solution · 2011

   Opposite direction

3. no effect
   Nitrogen reduction did not affect green or red lettuce yield.

   Effect of Reduced Nitrogen and Supplemented Amino Acids Nutrient Solution on the Nutritional Quality of Baby Green and Red Lettuce Grown in a Floating System · 2020

   Opposite direction

4. no effect
   Ziluoma yield was unaffected until nitrate dropped below 1.0 mM.

   Short-Term Nitrate Limitation Prior to Harvest Improves Phenolic Compound Accumulation in Hydroponic-Cultivated Lettuce (Lactuca sativa L.) without Reducing Shoot Fresh Weight · 2018

   Opposite direction

5. no effect
   Reducing N fertilization from 528 to 401 kg N ha-1 had no significant effect on yields

   N₂O fluxes from a Haplic Luvisol under intensive production of lettuce and cauliflower as affected by different N‐fertilization strategies · 2010 · compared with good agricultural practice

   Opposite direction

6. negative
   Urea yielded less than ammonium nitrate and calcium nitrate.

   Effect of temperature, carbon dioxide enrichment, nitrogen form and rate of nitrogen fertiliser on the yield and nitrate content of two varieties of glasshouse lettuce · 1992 · compared with other two N sources

   Opposite direction

7. negative
   The top application of urea suppressed lettuce yield.

   Growth and nutrient and nitrate accumulation of lettuce under different regimes of nitrogen fertilization · 2019

   Opposite direction

8. no effect
   Lettuce yields did not differ significantly across nitrogen treatments apart from the control.

   The Use of Green Manure Crops as a Nitrogen Source for Lettuce and Chinese Cabbage Production in Greenhouse · 2012 · compared with control (0 kg/ha)

   Opposite direction

70 papers more in this group