Ultrasol®ine K Plus for better root development and faster growth in lettuces

The application of Ultrasol®ine K Plus resulted in improved root development and faster plant growth, leading to earlier harvest in a series of trials on lettuce grown in water culture (Nutrient Film Technique in System, NFT).

Iodine (I) should be considered as a plant nutrient. This is the main conclusion of Kiferle et al., 2021. In that work, the presence and identity of natural iodinated proteins in higher plants was published, which had never been described before. Eighty-two iodinated proteins involved in important biological processes in higher plants have been identified. Like deficiency of any other plant nutrient, iodine deficiency can lead to yield losses.

In fertigation and protected horticultural crops grown in a commercial production environment, iodine deficiency can occur when the presence of iodine in the nutrient solution is below a target value of sufficiency. In intensive and fertigation under cover cropping systems, the nutrient solution and irrigation water are the main sources of iodine. This deficiency will manifest itself in the form of suboptimal root or leaf development, delayed flowering, reduced fruit growth and reduced stress resistance, resulting in lower yields compared to a crop that has been supplied with sufficient iodine in the nutrient solution.

To demonstrate the effect of improving iodine supply in an iodine-deficient crop, Ultrasol®ine K Plus (potassium nitrate containing a fixed amount of iodine) was applied as a source of K and N - and iodine - in the nutrient solution of four varieties of lettuce type 'Crispa' cabbage, 'Vanda', 'Milena', 'Brida' and 'Bruna', and cilantro in NFT hydroponics, with four different growers.

The size of the treated sectors varied among producers. On average, they contained 4-6 NFT tables, 1.5-2 m wide, constructed of galvanized steel pipe. Among the separately fertigation sectors, variety, planting date, plant density and general crop management were the same. The composition of the nutrient solution was determined according to the grower's usual practice. Two treatments were compared: in the control sector, the farmer's standard nutrient solution was prepared using potassium nitrate without iodine as the main source of K, while in the other, Ultrasol®ine K Plus was applied in the same amounts and with the same frequency.

At each of the 4 production sites, 10-15 heads or plants per sector were sampled shortly before harvest, at the same time after transplanting in both sectors, and weighed.

At one of the locations with two lettuce varieties at NFT, root length was additionally determined early in the crop cycle (13 days after transplanting, DDT) and for cilantro total plant length was measured at 20 DDT.

A beneficial effect was observed at all locations of Ultrasol®ine K Plus (potassium nitrate containing a fixed amount of iodine) application on root growth, already at the beginning of the crop cycle (Figure 1). A consistent improvement in lettuce head weight and cilantro plant weight and length was observed in NFT tables where Ultrasol®ine K Plus was applied compared to the control (Table 1, Figures 2 and 3). This could be interpreted as growth retardation in the control treatment, which lacks a sufficient supply of iodine in the recycled nutrient solution.

In particular, in water crops, the only iodine supply to these plants comes from irrigation water. This means that severe iodine deficiency was predicted to occur at these sites based on the low iodine concentrations measured in the irrigation water.

Iodine is present in proteins such as enzymes that control the redox balance in root oxygen supply, important for root development, and for proteins that manage electron flow during photosynthesis; these processes are important drivers of plant growth. For both lettuce and cilantro, faster biomass development translates into shorter crop cycles to the benefit of the grower. The product can reach the market on average 2 to 4 days faster (Figure 4), allowing more growing cycles to be included in a growing season.

Table 1. Average plant weight and root growth of lettuce and weight and *length of cilantro plants grown in a hydroponic system using the nutrient film system (NFT). The use of potassium nitrate without iodine in the control sectors (Control) was compared to the application of potassium nitrate with iodine(Ultrasol®ine K Plus). DDT=days after transplanting.

Figure 1. Brida' lettuce seedlings show faster initial growth 13 days after transplanting due to improved root development with Ultrasol®ine K Plus.

Figure 2. Rapid cilantro plant growth for earlier harvest with Ultrasol®ine K Plus.

Plant samples for the evaluation of plant weight and root growth of Crispa lettuce.

Figure 4. 23 days after transplanting in a summer crop, plants grown with Ultrasol®ine K Plus (potassium nitrate containing a fixed amount of iodine) in the nutrient solution are ready for harvest. Control plants will need an additional 2 to 4 days of growth before filling the market boxes.

The original publication is available at: https://doi.org/10.17660/ActaHortic.2021.1321.27