Impact of Macronutrient Fertility on Mineral Uptake and Growth of Lactuca sativa ‘Salanova Green’ in a Hydroponic System

Abstract

Lactuca sativa (commonly referred to as lettuce) is one of the most popular grown hydroponic crops. While other fertilizer rate work has been conducted on lettuce, the impact of each element has not been evaluated independently or by determining adequate foliar tissue concentrations when all nutrients are plant-available. This study explores the impact that macronutrients have on the growth and yield of lettuce at different stages of the production cycle. Additionally, this study explores the adequate nutrient rates by regressing nutrient curves to find the concentration of each element that corresponds to optimal growth. Plants were grown under varying macronutrient concentrations (0, 8, 16, 32, 64, and 100%) utilizing the concentrations of a modified Hoagland’s solution based on 150 mg·L−1 N. Lettuce plants were grown in a silica sand culture and received a nutrient solution in which a single element was altered. Visual symptomology was documented, and leaf tissue mineral nutrient concentrations and biomass were measured at Weeks 3, 6, and 8 after transplant. Optimal elemental leaf tissue concentration and biomass varied by macronutrient rates and weeks of growth. Nitrogen rate produced a linear increase in total plant dry weight, but foliar N followed a quadratic plateau pattern. Other elements, such as phosphorus, potassium, and magnesium, produced distinct total plant dry weight plateaus despite increasing fertility concentrations. These results demonstrate that fertility recommendation can be lowered for nutrients where higher rates do not result in higher plant biomass or foliar nutrient concentrations.

A Data-driven Approach for Generating Leaf Tissue Nutrient Interpretation Ranges for Greenhouse Lettuce

“…1, Tables 2 and 3). A recommended sufficiency range of 4.38% to 5.79% N expands the N sufficiency ranges of 4.2% to 5.6% N (Bryson et al 2014) and 4.8% to 5.5% N (Veazie et al 2022). In addition, the deficiency value of 2.84% N was similar to the 2.65% N reported by Henry et al (2018), confirming that <2.84% N is inclusive of previously reported deficiency values.…”

“…High foliar N concentrations can lead to lower boron (B), copper (Cu), and potassium (K) foliar concentrations (Marschner 1995). Veazie et al (2022) reported a quadratic plateau regarding N foliar concentration of 5.41% for 8-week-old lettuce grown using an N fertility rate of 111.4 mg•L À1 N. The Weibull distribution curve establishes 6.89% N as the boundary between high and excessive concentrations and offers a target value for possible future refinement.…”

“…Based on this curve, a recommended sufficiency range of 0.58% to 0.96% P would expand the upper P sufficiency range reported by Jones (2005) and overlap with the P sufficiency range reported by Bryson et al (2014). In addition, this range includes the plateau of 0.6% P reported by Veazie et al (2022) after 8 weeks of growth when plants were fertilized with up to 9.86 mg•L À1 P. Van Eysinga and Smilde (1981) considered <0.59% P to be deficient, but their recommended range of 0.40% to 0.92% P included that value. The P deficiency foliar concentration threshold of 0.27% P, based on the lowest 2.5% of the observations, was greater than the 0.13% P reported by Henry et al (2018) and confirms that this suggested deficiency range encompasses previously reported deficient values.…”

“…Providing nutrient fertility rates to promote optimum plant growth or yield without resulting in luxury consumption is an economic priority for growers. Veazie et al (2022) determined the impact of individual macroelement fertility concentrations on lettuce growth and how fertility requirements varied throughout the production cycle. These studies provided insight into the optimal leaf nutrient concentrations for lettuce, yet with this crop being of such importance in the industry, further refinement of nutritional ranges is needed.…”

Role of silicon and silicon fertilizers in the world: a review of papers from the Scopus database published in English for the period of 2012–2022

“…Silicon plays a very important role in the absorption of such ions by plant tissues (Pavlovic et al, 2021). According to the article, among the macronutrients, nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg) and calcium (Ca) are affected differently and not separately (Veazie et al, 2022). In addition, Si also plays an important role in plant uptake of certain trace elements such as boron (B) and manganese (Mn) (Pavlovic et al, 2021).…”