Biofumigation With Pellets of Defatted Seed Meal of Brassica carinata: Factors Affecting Performance Against Phytophthora nicotianae in Pepper Crops

Abstract

Phytophthora nicotianae is the pathogen that causes root and crown rot disease in open field paprika pepper crops of Extremadura (central-western Spain). A field experiment was established during spring, a period compatible with the pepper crop cycle in this region, to evaluate the effects of biofumigation with pellets of Brassica carinata defatted seed meal, at the rate recommended by the manufacturer (3 tons ha−1), on the survival and infectivity of P. nicotianae chlamydospores inoculum. Furthermore, three biofumigant rates (3, 6, and 20 tons ha−1) were assayed in laboratory experiments with natural soil inoculated with chlamydospores. In the field trial, the incorporation of pellets at 3 tons ha−1 did not produce remarkable changes in soil enzyme activity or soil properties. In both the field and laboratory tests, survival and infectivity in the biofumigated treatment at 3 tons ha−1 did not differ from those in the untreated control. On the contrary, the same rate added to autoclaved soil completely suppressed the inoculum, suggesting that the soil microbiota degrades B. carinata pellets before being effective against P. nicotianae. Increasing the recommended rate to 6 tons ha−1 decreased inoculum survival in the laboratory test and 20 tons ha−1 completely inhibited the inoculum, although the economic value of such a high rate application is a factor to be assessed. In phytotoxicity tests on radish and white mustard seeds with several concentrations (100, 50, 25, 10, 5, and 0%) of B. carinata pellets solution, no phytotoxic effect was observed with the two lowest concentrations, and no symptoms of phytotoxicity were found in the bioassays of pepper plants.

Brassica carinata Seed Meal as Soil Amendment and Potential Biofumigant

“…The resulted values were 1.41, 1.51, 1.75 and 4.28% for control soil, D, 10D and 100D soils, respectively; being the soil under investigation a clay loam soil, where OM% results in a low content in the range of 1.2-2.2% and in high content in the range >3.0%, it can be concluded that only the addition of seed meal at 100D really improves the OM content of the soil under experiment, supplying a very high amount of fresh organic matter. In contrast, the addition of the meal at doses D and 10D let stand the soil in the same class of OM content as the control soil, even if a slight increase is recorded, similarly to what was observed by Serrano-Pérez et al [57] at the dose of 3 ton/ha.…”

“…Other studies conducted with B. carinata pellets at similar doses to 10D β-glucosidase and phosphatase activities were not significantly different from the control [57,85]. On the contrary, for Zaccardelli et al [22], the β-glucosidase and phosphatase are significantly increased compared to control after one month, and the arylsulphatase seems to be influenced in the short term with a slight increase compared to the control followed by a stabilisation as observed in the present study at the same dose tested (10D).…”

“…The acidity of the seed meals (pH = 5.28) could be the factor that contributed to the pH decrease, and this could be useful when the meal is applied to alkaline soils. Despite this, other authors argued that pH changes by approximately 0.5 after adding B. carinata pellets were considered negligible [57].…”

“…Brassica c. seed meal was incorporated into the soil at a rate of 0.1 g (Trial "D"), 1 g (Trial "10D") and 10 g (Trial "100D") per 100 g of soil. The first dose corresponds to 3 tons, a quantity normally distributed per hectare as a soil amendment [57]; the other two doses were tested only for experimental purposes considering that they are not applicable in agricultural practice, but their detection could provide important general information on the transformation of organic matter in the soil.…”

Biodisinfection as a Profitable Fertilization Method for Horticultural Crops in the Framework of the Circular Economy

“…In the IF block, Brassica carinata pellets were used repeatedly, while in the PD block, it was tomato plant debris. Núñez-Zofio et al [34] and Serrano-Pérez et al [59] reported that Brassica carinata pellets (with biosolarization) showed a limited capacity to improve the chemical quality of the soil. The organic amendment could not improve any of the chemical properties of the soil versus a treatment without the addition of any organic amendment and without applying solarization.…”