Growth and development of pepper are affected by humic substances derived from composted sludge

Abstract

A greenhouse experiment was conducted to evaluate the effects of humic substances extracted from composted sewage sludge on growth, phenological development, and photosynthetic activity of pepper (Capsicum annuum L. cv. Piquillo) plants. Humic substances derived from composted sludge (HSS) were compared with those derived from leonardite (HSL). Two doses of both humic substances were assayed (200 and 500 mg C [L substrate] -1 ) and compared with a control (C). HSS showed higher nitrogen content and a higher percentage of aliphatic carbon, as well as a lower content of aromatic and phenolic carbon than HSL. HSS significantly increased plant dry-matter production (up to 560%), plant height (86%-151%), and leaf area (436%-1397%) during the early stages of pepper development. Net photosynthesis and stomatal conductance increased in the treatments with HSS (up to 48% and 63%, respectively) at the vegetative stage. In addition, HSS accelerated the phenological development of pepper plants, reducing significantly the number of days to flowering and ripening, which occurred 12 and 14 d earlier than in control plants, respectively. In general, the treatments with HSS and HSL did not markedly affect chlorophyll and nutrient concentrations in the leaves. At maturity, only small differences in total fruit yield, number of fruits per plant, and fruit size were observed between amended and control plants. The results suggest that the mechanisms through which HSS affected plant growth and development were not associated with an improved nutrient uptake. Although the identity of the growth-promoting factors remains to be found, the results suggest that they may be linked to the chemical structure of the humic substances.

The use of organic biostimulants in hot pepper plants to help low input sustainable agriculture

“…In particular, previous studies reported the improvement of pepper plant biomass and yield by either natural biostimulants [26] or humic substances from composted sludge [13]. Accordingly, RG and AH application to plants resulted in increased leaf biomass and weight of green peppers at the flowering stage, as well as in increased red pepper number and growth at maturity.…”

“…In particular, they decrease the use of mineral fertilizers by increasing the amount of micro-and macro-nutrients taken up by plants, positively influencing root morphology and plant growth [9,10]. They also display hormone-like activity and influence plant metabolism by interacting with biochemical processes and physiological mechanisms, such as glycolysis and nitrogen assimilation [11,[12][13].…”

“…In recent studies, the application of products with biostimulant action to pepper plants was found to exert positive effects on plant growth and yield without loss of fruit quality [13,17,18]. Pepper is an important agricultural crop due to the nutritional value of its fruits, which are an excellent source of a wide array of phytochemicals with well-known antioxidant properties.…”

Nutrient acquisition and eucalyptus growth affected by humic acid sources and concentrations

“…According to Pinheiro et al (2010), increase in HA concentration in nutrient solution drastically reduced accumulation of Fe, Cu, and Zn; however, for Mn, this effect was not so pronounced as for Fe, Cu, Zn and B; depending on the source, Mn accumulation improves when the concentration of 10 mg L -1 C-HA is used. Application of HA increasing macronutrient accumulation in plants is shown in greater magnitude for N, P, K, and Ca (AZCONA et al, 2011;EKINCI et al, 2015;MELO et al 2015;TAVARES et al, 2017), whereas, for S and Mg, this effect may be small or null (AZCONA et al, 2011;PINHEIRO et al, 2010).…”

“…According to Rose et al (2014), the source of HA modulates its effect on plants by changing pH, EC, nutrient concentrations, presence of organic acids, molecular weight, presence of hormones, and other substances that play an important role in plant physiological and biochemical processes, mainly those HA derived from composted sources (MARTINEZ-BALMORI et al, 2014;ROSE et al, 2014). The effect of the HA source is dependent on the concentration used, which affects nutrient acquisition by plants (AZCONA et al, 2011), considered that compostderived HA are more chemically bioactive and requires lower optimal concentrations to positively affect plants (GARCÍA et al, 2016;ROSE et al, 2014).…”