Santos-Haliscak et al. 2016 JPACD (2016)18:52-64 52 Effects of compost level in soil and season on the production and composition of cactus varieties Santos-Haliscak, J. A. 1* , Kawas, J. R. 1 , Fimbres-Durazo, H. 1 , Moreno-Degollado, G. 1 , Vázquez-Alvarado, R.E. 1 , Olivares-Sáenz, E. 1 , Andrade-Montemayor, H. 2 1 Universidad Autónoma de Nuevo León, Posgrado Conjunto de las Facultades de Agronomía y Medicina Veterinaria y Zootecnia. Ave. Universidad S/N, Cd. Universitaria, San Nicolás de los Garza, N. L., México. CP 66455. 2 Universidad Autónoma de Querétaro, Facultad de Ciencias Naturales. Campus Juriquilla. Ave. de las Ciencias S/N. Juriquilla Delegación Santa Rosa Jáuregui, CP. 76230. Querétaro, México. * Corresponding author: j3santos@gmail.com Received: June 24, 2016; Accepted: December 27, 2016. ABSTRACT The objective of this research was to determine the effect of adding compost on nutritive value of cactus cladodes during the four seasons of the year. The production, chemical composition, and in vitro digestibility of a cactus variety with spines (WS) and a cactus variety without spines (WOS), were subjected to a complete block design with three quantities of compost (0, 61 and 122 t ha -1 ) and four seasons (summer, fall, and winter 2013 and spring 2014). The WS variety produced more dry matter (DM) (p=0.035) and crude protein (CP) (p=0.037) than the WOS variety. Although CP, fiber constituents, and mineral composition of cactus varied (p<0.001) with respect to season of the year, in vitro DM digestibility did not differ (p=0.29) across seasons. Both cactus varieties had high ash (29.0 to 29.2%) and moisture (89.5 to 91.7%) contents. Adding compost to the soil improved (p<0.001) the average DM production of both cactus varieties. Compost addition also increased the lignin (p=0.008), phosphorus (p<0.001) and zinc (p=0.025) concentrations and reduced (p=0.04) the in vitro DM digestibility. The high ash and moisture contents of cactus could reduce the densities of energy and other nutrients that are consumed by livestock. Keywords: Cactus, compost, fiber, protein, minerals, in vitro digestibility. INTRODUCTION In Mexico, cacti (Opuntia spp.) have been used as a vegetable, fruit, and fodder since pre- Hispanic times. Combined with corn and agave, cacti were important in the growth of the Aztec civilization (Kueneman, 2001). Surface area with wild cacti exceeded three million hectares