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Nitrogen overfertilization is a common horticultural practice in central Chile, leading to the risk of nitrate leaching and contamination of aquifers and groundwater. The aim of the present study was to evaluate the effect of organic amendments on NO3 - leaching. Three sites with different management systems were selected: Agroecological (AE, 3-yr agroecological management), Transition (TR, starting agroecological management), and Conventional (CN, traditional conventional management). Two lettuce (Lactuca sativa L.) growing cycles (autumn-winter and spring-summer) were implemented at each site. Nutrition at AE and TR was based on organic fertilizers and microorganisms, and inorganic N fertilizers were used at CN. The pore water was sampled at the beginning and at the end of each cycle at the 70 cm depth. Lettuce yields and unit weight were measured. There was a significant effect of the site and time of sampling (both p = 0.000) on the NO3 - concentration in leached water. At the beginning of the first cycle, nitrate leaching was 2.2 times higher at TR and CN (370 ± 81 mg L-1) compared with AE (163 ± 54 mg L-1), reflecting the loss of previously accumulated soil N. Afterward, leaching at CN remained higher than at AE and CN, significantly varying between sampling times; however, it decreased by 37% to 80% compared with the initial measurement. Leaching at both AE and TR remained stable within a low range of 38 to 96 mg L-1. Results showed that organic soil management is able to maintain a low rate of nitrate leaching in the soil compared with conventional management.

Seed quality has been an important factor in achieving high germination and uniform growth rates in agricultural crops. Meanwhile, pepper plants are moderately sensitive to salt stress at electrical conductivity (EC) in the nutrient solution in the range of 1.2–3.0 dS m−1. We are unaware of any studies regarding the effects of mother plant saline stress on the agronomical quality of pepper seeds. We assessed the effects of three levels of electrical conductivity of the nutrient solution used for mother plant fertigation (2.2, 3.5, and 4.5 dS m−1) on the agronomical quality of pepper seeds (Capsicum annuum L. var. California Wonder). We have analyzed the following seed quality traits: (1) size and weight of seeds and number of seeds per fruit, (2) seed germination and vigor, and (3) chemical composition and histological features of mature seeds. The electrical conductivity treatment of 3.5 dS m−1 caused a statistically significant reduction in the seed size and vigor, as well as partial histological damage to seed endosperm. Moreover, the electrical conductivity treatment of 4.5 dS m−1 caused further reduction in the seed agronomical quality and generalized histological damage to seed endosperm. The electrical conductivity of the nutrient solution used for the fertigation of mother pepper plants should be below 3.5 dS m−1. Future studies should be performed to better gauge the effect of nutrient solutions with electrical conductivity in the range of 2.2–3.5 dS m−1 on the seed quality traits.

Several studies have reported the presence of smithsonite (ZnCO3 ) in soils polluted by zinc mining. The present study aimed to determine upper critical threshold values of Zn phytotoxicity in a substrate spiked with ZnCO3 and to compare them with those obtained in field-collected soils. We studied Zn toxicity to perennial ryegrass (Lolium perenne L.) grown in pots with unpolluted peat treated with increasing concentrations of ZnCO3 that produced nominal total Zn concentrations of 0, 0.7, 1.3, 2.0, 2.6, and 3.3%. To keep constant near-neutral pH value in all the treatments, we used decreasing concentrations of dolomitic lime. In the treatment with total soil Zn of 3.3% (pH 6.8), the foliar Zn concentration of L. perenne was 1914 ± 211 mg kg-1 , falling into the range of 2400 ± 300 mg kg-1 reported for Lolium species grown under similar laboratory conditions in a polluted soil (total soil Zn 5.4%, pH 7.3) collected near a Zn smelter. The value of 92 ± 98 mg kg-1 was obtained for the median effective concentration (EC50) values of 0.01 M KNO3 -extractable Zn using the responses of shoot dry biomass, shoot length, and total pigments. This value falls within the range of 95 ± 46 mg kg-1 reported in other studies for the EC50 values of salt-extractable Zn using field-collected soils. The application of ZnCO3 for spiking was able to mimic foliar Zn concentrations of Lolium species observed in field-collected soils. The effective concentrations of soil Zn obtained in the present study are comparable to those obtained in field-collected soils. Future research should determine effective concentrations of metals using soils spiked with metal-containing compounds that mimic a real source of contamination. Environ Toxicol Chem 2020;39:1790-1796. © 2020 SETAC.

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Human exposure to trace elements has been a large concern due to the potential health issues. Accordingly, this study aimed to compare the concentrations of arsenic, copper, and zinc in the edible parts of vegetables grown in a mining-agricultural area and in an exclusively agricultural area and to compare the potential human health risks of consuming vegetables from both areas. The consumption habits of the studied population were extracted from the 2010 National Alimentary Survey of Chile. In most cases, the concentrations of trace elements in the edible tissues of vegetables (lettuce, spinach, garlic, onion, carrot, potato, sweet corn, and tomato) were higher in the mining-agricultural area than those in the control area. This difference was most pronounced for leafy vegetables, with arsenic being the trace element of concern. Specifically, the arsenic concentrations in the edible tissues of lettuce and spinach were 8.2- and 5.4-fold higher, respectively, in the mining-agricultural area than in the control area. Lettuce was the vegetable of concern due to its relatively high consumption and relatively high concentration of trace elements. Nevertheless, there was no health risk associated with vegetable consumption in either the mining area or the control area because none of the HQ values surpassed 1.0.