## 2 Materials and Methods  
### The Study Area  
The research was conducted at Primavera Farm, located in the municipality of Paramirim in the semiarid region of Pernambuco State, Brazil. The experimental area is situated in the Brigida River Basin (see Figure 1). The soil in the experimental area is classified as Fluvisol [25], which presents a flat topography. The region is characterized by the Caatinga biome. Figure 1d illustrates the experimental plot with 0.25 hectares, while Figure 1e shows the intercropped cultivation of forage cactus (_Opuntia stricta_ (Haw.[PERSON] [PERSON]) with gliricidia (_Gliricidia sepium_) and moringa (_Moringa oleifera_). The experimental area is part of a scientific project carried out by the Federal Rural of Pernambuco, addressing irrigation reuse and entrepreneurial activities, aiding local farmers to cope with water scarcity in the Brazilian semiarid region.  
Forage cactus was cultivated in May 2021 without irrigation. Subsequently, irrigation with treated wastewater effluent was initiated in November 2021, along with the planting of intercropped moringa and gliricidia. Forage cactus was cropped with a spacing of 2.5 \(\times\) 0.5 m (double row), totaling ~13,300 plants ha\({}^{-1}\). Gliricidia and moringa were planted adopting a 1.0 m spacing between rows, totaling ~4000 plants ha\({}^{-1}\). Those crops were arranged in rows, positioned 1.25 m from the forage cactus lines in intercropped plots. The plot comprised eleven rows, each 6 m long, including six rows of forage cactus and five of intercropping. Two soil cover conditions were considered: bare soil and mulch, composed of plant residue straws, applied at a density of 8 Mg ha\({}^{-1}\). Treated domestic effluent from  
Figure 1: Location of the study area (**a**), climatic classification (**b**), hypsometry (**c**), experimental plot (**d**), and images of the intercropped system (**e**). Aw: tropical savanna climate with a dry winter season; BWh: hot arid climate; BSh: hot semiarid tropical climate with a defined dry season.  
the Sewage Treatment Plant operated by the \"Companhia Pernambucana de Saneamento\" (COMPESA) was used for irrigation.  
The regional climate is classified as tropical semiarid (BShw), with a wet season from November to April [26]. The average temperature is 26 \({}^{\circ}\)C, with mean annual precipitation of 569 mm, and potential evapotranspiration being approximately 1600 mm [27]. The remote sensing investigation was conducted on 31 January 2023, and climate information is presented in Figure 2, recorded by a Campbell Scientific weather station located near the experimental area. For the calculation of crop evapotranspiration (CET), the potential evapotranspiration (PET) was multiplied by the crop coefficient (Kc) of 0.52. The PET was estimated using the Penman-Monteith method standardized by FAO Bulletin 56 [28].  
On 31 January 2023, nearly 15 months after starting the irrigation, morning and gliriicidia presented mean values of crop height, stem diameter, and maximum canopy width of 2.13 m, 53.24 mm, and 0.8 m; 1.42 m, 25.75 mm, and 1.23 m, respectively. For forage cactus, the mean values for height, canopy size, and number of cladodes were 0.66 m, 0.80 m, and 12.6 cladodes, respectively.