Effects of Boron Applications on the Physiology and Yield of Lettuce

The application of hydroponic cultivation fertilized with biologically nitrified synthetic urine can produce nitrate-rich fertilizer for lettuce (Lactuca sativa var. capitata L.). The mounting water crisis and depletion of natural resources makes nitrogen recovery from human urine a practical option. Nitrified urine can be used in indoor vertical hydroponic cultivation and is characterized by a high degree of element recovery. Because of its high ammonium content, hydrolyzed fresh urine may be toxic. A nitrification sequencing batch reactor with suspended activated sludge biomass ensured urine stabilization and biological conversion into nitrate-rich fertilizer. The diluted nitrate-rich fertilizer was then supplied for soilless cultivation. The results show that diluted nitrified urine is an excellent source of bioavailable nitrogen and phosphorus and, with proper enrichment with microelements, could replace commercial fertilizers in hydroponic systems. The yield and quality parameters of lettuce cultivated with enriched urine were comparable to those obtained with a commercial fertilizer. The mass balance calculation showed that industry-scale lettuce production can be based on urine fertilizer collected from a few hundred people for a single unit.

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“…The boron content in the lettuce leaves (33.1-42.3 mg B•kg −1 ) fell within the range of 15-84 mg B•kg −1 given by Sahin et al [54].…”

Section: Nutrient Content Levelssupporting

confidence: 78%

Resource Recovery from Synthetic Nitrified Urine in the Hydroponic Cultivation of Lettuce (Lactuca sativa Var. capitata L.)

et al. 2021

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“…The root growth inhibition could be caused by the reduction in the meristem size due to the reduction in cell division [59,60] or by the disruption of cytoplasmic metabolism, resulting from boron toxicity [61]. It was also reported that the high doses of boron fertilizer increased enzymatic antioxidant activity in lettuce in order to decrease the stress damage [62]. A previously published study identified the root tip as a site of boron toxicity because an inhibition of root growth occurred if the excess of boron was applied to the root tip region but not if the excess of boron was applied to the mature sections of the root [63].…”

Section: Acute Toxicitymentioning

confidence: 99%

Ecotoxicity Study of Additives Composed of Zinc and Boron

Petrová

Soudek

2022

Toxics

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The high use of additives containing zinc borate and their limited solubility in water both lead to its persistence and accumulation in biological systems. On the other hand, soluble forms of boron are easily available to plant roots and are taken up by plants. There are no ecotoxicological data available for zinc borate, the industrial utilization of which is widespread. Therefore, the potential toxicity of zinc borate and its dissociated compounds was evaluated. Based on two different ecotoxicology tests, their effect on plant growth was studied. Firstly, the impact on Lemna minor growth was investigated, including the effect on pigment content. Secondly, the inhibition of the root growth of higher plant species Sinapis alba (mustard), Lactuca sativa (lettuce) and Trifolium pretense (clover) was measured. The growth inhibition test on L. minor was more complex and sensitive compared to the plant seed germination test. Already low concentrations (10 mg/L) of ZnO, B2O3 and Zn3BO6 led to a decrease in frond growth and to an inhibition of the conversion of chlorophyll a to chlorophyll b. These results suggested that the stress caused by these additives caused damage to the photosynthetic apparatus. The highest inhibition of frond growth was detected in fronds treated with B2O3 (92–100%). In ZnO and Zn3BO6, the inhibition of frond growth was between 38 and 77%, with Zn3BO6 being slightly more toxic. In the seed germination test, the most sensitive species was lettuce, the growth of which was inhibited by 57, 83 and 53% in ZnO, B2O3 and Zn3BO6 treatments, respectively. However, the inhibitory effect on each plant was different. In lettuce and clover, the seed germination and root elongation decreased with increasing element concentrations. In contrast, in mustard, low concentrations of ZnO and Zn3BO6 supported the growth of roots. For that reason, more complex tests are essential to evaluate the additive toxicity in the environment.

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