Substrato de casca de arroz in natura e condicionadores para a cultura do morangueiro em sistema com recirculação da solução nutritiva

Abstract

The soilless culture technique has been adopted in strawberry production by many farmers in Rio Grande do Sul (RS), Brazil. Issues related to substrates and fertigation management used in this cultivation system with drainage and recirculation of nutrient solutions are some bottlenecks of the system. Thus, this study aimed to evaluate the possibility of using raw rice husk (RRH), in mixtures with different substrate conditioners, to make its use feasible in national transplant production, in addition to fruit growth and production. Three experiments were carried out. Experiment 1 evaluated the effect of three substrate conditioners, i. e., medium grade vermiculite, carbonized rice husk (CRH) and commercial substrate S10 Beifort® (S10), in ratios of 35% mixed with 65% RRH, to produce national bare root transplants on cultivation benches (1.7 m 2 ) with stock plants of cv. Aromas. Experiment 2 evaluated the effect of two substrate conditioners (CRH and S10) mixed with 80% RRH on strawberry growth and production, through national bare root transplants and plug plants, in addition to partial maintenance of the latter, in the second year of cultivation, and compared them to new transplants grown on the same substrate. Experiment 3 evaluated the effect of substrate conditioners on strawberry transplants grown on new and reused substrates and compared their use cycles. Experiments were carried out in a greenhouse located on the campus of the Universidade Federal de Pelotas, in Pelotas, RS, Brazil. In experiment 1, the substrate formulated with S10 obtained the highest number of transplants and propagules, besides ensuring the highest production of grade 3 transplants (≥ 8.1 mm). Substrates formulated with vermiculite and CRH showed the highest production of Grade 2 transplants (from 5.0 to 8.0 mm). In experiment 2, substrates formulated with S10 exhibited the highest dry fruit mass (DFM) and above ground plant dry mass (AGPDM) with plug plants, which are more productive than bare root transplants in all substrates, while bare root transplants showed high AGPDM in RRH+CRH, but lower productivity and average fruit mass (AFM) in this substrate. Regarding plant age, plants in the second cultivation period showed higher vegetative growth, larger number of fruits and higher commercial productivity in RRH+CRH and 100% RRH, while plants in the first cultivation period exhibited higher AFM. RRH+S10 increased DFM, number of fruits and commercial productivity of plants in the first cultivation period. In experiment 3, RRH+S10 promoted high commercial productivity in both substrate cycles. Values of growth and productivity exhibited by 100% RRH were similar to the ones found by RRH+S10, a fact that shows that both substrates were reused. On average, new substrates exhibited the highest AFM and ascorbic acid content, while reused ones showed the highest commercial productivity (except RRH+CRH+S10) and contents of total soluble solids and phenolic compounds.