Red pitaya (Hylocereus costaricensis) is a promising species, with high cultivation potential due to the organoleptic and functional qualities of its fruits. However, irrigation water salinity can affect the crop yield. Therefore, materials rich in organic substances can minimize the damage caused by excess salts in soil and/or water. Thus, the objective of this study was to evaluate the influence of organic matter sources as attenuators of salt stress on the production and biochemical responses of red pitaya seedlings. A completely randomized design in 4 × 5 factorial scheme, with five sources of organic matter (humus, sheep manure, biofertilizer, organic compost and sand + soil) and four salinities (0.6, 2.6, 4.6 and 6.6 dS m^-1) with four replicates and two plants per plot was used. The shoot length, root length, cladode diameter, number of cladodes, number of sprotus, root volume, shoot dry mass, root dry mass and total dry mass, root and shoot dry mass ratio, chlorophyll a, b and total, amino acids and soluble sugars were evaluated at 120 days after the treatments began to be applied. Red pitaya is moderately tolerant to salinity (ECw from 4.0 to 6.0 dS m^-1). Organic compost and sheep manure attenuate the harmful effects of salinity on red pitaya seedlings. Under salt stress conditions, red pitaya plants increase their levels of proline, amino acids and total sugars.

This work summarizes information about organic nitrogen (N) in the agricultural system. The organic N forms in soils have been studied by identifying and quantifying the released organic compounds when soils are acid treated at high temperature, in which the following organic N fractions are obtained: hydrolyzable total N, subdivided into hydrolyzable NH4+-N, amino sugars-N, amino acids-N, and unidentified-N and acid insoluble N, a fraction that remains associated with soil minerals after acid hydrolysis. Nitrogen mineralization and immobilization are biochemical processes in nature. This chapter summarizes how these processes occur in the agricultural system. Then, soluble organic nitrogen (SON), volatilization and denitrification processes, and biological nitrogen fixation (BNF) as a key component of the nitrogen cycle and how it makes N available to plants are also discussed. Finally, we discuss the use of organic fertilizers as N source to satisfy the worldwide demand for organic foods produced without synthetic inputs.

The need to diversify agricultural production has fostered the cultivation of several crops under environmental conditions atypical to their origin, justifying the extreme importance of studies on the agricultural management of crops in semiarid regions. In this context, this study aimed to evaluate the effects of irrigation depth and potassium doses on fig quality under semiarid conditions. The experiment was conducted in a 4 × 4 split-split-plot design, in randomized block design, with three replicates. The plots corresponded to four irrigation levels (50%, 75%, 100%, and 125% ETc), the subplots consisted of four potassium doses (0, 60, 120, and 240 g K₂O plant⁻¹), and the sub-subplot corresponded to the crop years (2018/19 and 2019/20). Results showed that water deficit reduced fig productivity, and the irrigation levels equal to or greater than 100% ETc performed cumulatively throughout the growing cycles. Therefore, irrigation depths from 85.19% to 95.16% ETc are recommended for greater water-use efficiency and fruit quality. Furthermore, potassium fertilization mitigated water stress in fig plants, allowing for reduced irrigation levels, especially in the second year, without compromising fruit traits.

LEAF AREA OF Erythrina velutina Willd. (FABACEAE) THROUGH ALLOMETRIC EQUATIONS