Vermicompost Leachate, Seaweed Extract and Smoke-Water Alleviate Drought Stress in Cowpea By Influencing Phytochemicals, Compatible Solutes and Photosynthetic Pigments

Drought is a major constraint for agricultural production worldwide and is likely to become aggravated by global warming. It can induce land degradation, exorbitant food prices and menace livelihoods. Approaches for retaining optimal yield, especially in rainfed staple crops such as cowpea (Vigna unguiculata) are paramount. Biostimulants; vermicompost leachate (VCL), seaweed extract [Kelpak® (KEL)] and smoke-water (SW) have exhibited effective amelioration for plants under abiotic stresses, however, research on cowpea remains scarce. Therefore, this study aimed to investigate the effects of seed priming of cowpea with VCL, KEL and SW on the growth, photosynthesis and biochemical levels in cowpea cultivated under three watering regimes. SW treatment amplified growth variables (i.e., foliage, shoot height, root length and number of flowers) of water-stressed cowpeas. KEL- and VCL-treated seeds significantly augmented shoot and nodules production by 2 and 4-fold respectively, compared to the control. Leaf carbohydrates and photosynthetic pigments in KEL- and SW-treated plants increased considerably under severe water deficits, while leaf proteins decreased by more than 3-fold. The biostimulants also lowered phenolic and flavonoid concentrations. Increasing and decreasing levels of soluble sugars, proteins, photosynthetic pigments, phenolics and flavonoids indicate stress alleviation and osmotic adjustment to water deficits. These biostimulants are a suitable alternative to improve soil fertility, growth, and yield of staple crops under water stress conditions.

Germination of Salicornia bigelovii (Torr.) under Shrimp Culture Effluents and the Application of Vermicompost Leachate for Mitigating Salt Stress

Attenuators of salt-stress favor the use of effluents, being a low-cost organic product. The present study aimed to evaluate the effect of vermicompost leachate (VL) added to shrimp-culture effluent on seeds and seedlings of Salicornia bigelovii (Torr.) under salt-stress, evaluating germination, water relations variables, and biomass. Seeds were irrigated with distilled water (DW) (CE: 0.0027 dS m−1), freshwater (FW) (CE: 1.36 dS m−1), seawater (SW) (CE: 55.83 dS m−1), shrimp residual water (SRW) (CE: 59.85 dS m−1), and with the same water sources but adding VL in 1:20 v/v. The means for the index of germination rate (IGR), germination energy (GE), and germination time (MGT) were higher with DW, DWVL, FW, and FWVL, decreasing with the others (p ≤ 0.05). In seedlings, the lowest water potential (Ψw) and osmotic potential (Ψs) were observed with SW, SWVL, SRW, and SRWVL (p ≤ 0.05), evidencing higher stress but the highest relative water content (RWC). The fresh and dry biomass increased and showed significant differences with SRW, and adding VL (DWVL, FWVL, SWVL, and SRWVL) acted as an effective attenuator of salt-stress. The response of water relations variables suggested an osmotic adjustment for mitigating the salt-stress in seedlings, lowering the Ψw and Ψs but increasing the RWC.

Respuestas de crecimiento, contenido de clorofila y rendimiento a la aplicación de lixiviado de vermicompost de estiércol bovino en el pimiento (Capsicum annuum L. híbrido Quetzal)

Growth, chlorophyll content and yield responses after application of bovine manure vermicompost leachate in pepper (Capsicum annuum L. Quetzal hybrid) Resumen El pimiento (Capsicum annuum L.) está presente en la dieta alimenticia de numerosas personas y tiene un gran valor económico para los agricultores que se dedican al cultivo de esta hortaliza. La presente investigación se realizó en la Facultad de Ingeniería Agronómica de la Universidad Técnica de Manabí, en el campus experimental La Teodomira. Se evaluó el comportamiento del híbrido de pimiento Quetzal F1 en cinco tratamientos: la aplicación foliar de tres diluciones (1:10, 1:20 y 1:30 v/v) de lixiviado de vermicompost de estiércol bovino (LVEB), fertilización química y suelo sin fertilización. Las variables evaluadas fueron la altura de la planta, el diámetro del tallo, la cantidad de hojas, el contenido de clorofilas totales y el peso de los frutos. A partir de esta última se estimó el rendimiento por hectárea. En general, los valores de todas las variables fueron significativamente superiores en las plantas que fueron tratadas con las diluciones de LVEB con respecto a las que crecieron en suelo sin fertilizar o con fertilización química. La dilución 1:30 del LVEB se destacó por encima de las restantes, mostrando incrementos significativamente mayores que la fertilización química en la altura de planta, el diámetro del tallo, la cantidad de hojas, el contenido de clorofilas totales, y aumentando en 1,28 tha-1 el rendimiento en comparación con las plantas que recibieron fertilizante químico. Los resultados demuestran los efectos benéficos que ejerce el lixiviado de vermicompost de estiércol bovino en el pimiento y potencian a este bioestimulante como alternativa sostenible en la producción hortícola. Palabras clave: pimiento; lixiviados; vermicompost; bioestimulantes Abstract The pepper (Capsicum annuum L.) is present in the diet of many people and has great economic value for farmers who are dedicated to the cultivation of this vegetable. This research was carried out at the Faculty of Agronomic Engineering of the Technical University of Manabí, on the La Teodomira experimental campus. The behavior of the Quetzal F1 pepper hybrid was evaluated under five treatments: foliar application of three dilutions (1:10, 1:20 and 1:30 v/v) of bovine manure vermicompost leachate (LVEB), chemical fertilization and soil without fertilization. The variables evaluated were the plant height, the diameter of the stem, the number of leaves, the total chlorophyll content and the weight of the fruits. From the latter, the yield per hectare was estimated. In general, the values ​​of all the variables were significantly higher in the plants that were treated with the dilutions of LVEB with respect to those that grew in soil without fertilizing or with chemical fertilization. The 1:30 dilution of the LVEB stood out above the remaining ones, showing significantly greater increases than chemical fertilization for plant height, stem diameter, leaf quantity, total chlorophyll content, and increasing yield by 1,28 tha-1 compared to plants that received chemical fertilizer. The results demonstrate the beneficial effects exerted by the bovine manure vermicompost leachate in pepper and enhance this biostimulant as a sustainable alternative in horticultural production. Keywords: pepper; leachates; vermicompost; biostimulants.

Ecological nutrient solutions on yield and quality of melon fruits

Due to health benef its, organic food products have increased their demand in recent years. The objective was evaluating the effects of three ecological nutrient solutions, (Tea of compost, vermicompost, and leachate of vermicompost), on yield and quality of melon plants. As a control, an inorganic nutrient solution was used. Our results showed that compost tea promoted fruit yield equivalent to the inorganic nutrient solution. Plants fertilized with compost tea yielded fruits with the highest value of soluble solids content (9.98 ºBrix). Regarding antioxidant capacity, fruits fed with compost tea and vermicompost leachate obtained higher values than fruits fed with nutrient solution, fruits fed with vermicompost leachate obtained statistically higher values than fruits fed with chemical nutrient solution. Concerning to total phenolic content plants fed with vermicompost leachate obtained the highest value statistically similar to control plants fed with the Steiner nutrient solution.

Vermiliquer (Vermicompost Leachate) as a Complete Liquid Fertilizer for Hydroponically-Grown Pak Choi (Brassica chinensis L.) in the Tropics

The processing of organic wastes and composts by worms results in castes and vermiliquer (i.e., vermicompost leachate). Both castes and vermiliquer contain plant available nutrients, the latter better suited to hydroponic operations, but the optimum pH for worm productivity and vermiliquer production makes the latter too alkaline for hydroponics. We show that under optimal hydroponic management practices, the growth and yield of pak choi (Brassica chinensis) based entirely on pH buffered vermiliquer collected after 8–10 weeks of vermicomposting was comparable with those treated with a conventional inorganic hydroponic fertiliser. Nitric acid proved to be a superior pH buffer compared with orthophosphoric acid. The total fresh weight in the nitric acid buffered vermiliquer treatments ranged from 70% to 98% of the total fresh weight of the control. However, the non-buffered hydroponic production of pak choi using off-line (batch) vermiliquer or direct linkage with vermifarms was not successful. There were no statistically significant differences between pak choi yields using vermiliquer from kitchen wastes or composted paunch materials. A 50% dilution of vermiliquer led to yield loss, but less proportionately than the dilution, and the use of pot hydroponics rather than nutrient film technique (NFT) hydroponics led to a better performance of pak choi under less favourable conditions. This is the first report of comparable yields between vermiliquer treatments and an inorganic nutrient source and highlights the feasibility and commercial potential of this hydroponic practice.