Comparison of continuous and rotational silvopastoral systems for established walnut plantations in southwest Missouri, USA

Forty-eight Holstein steers (average weight 243 kg ± 11.8) were utilized to study the performance of cattle grazing a mature walnut stand. Steers were grazed for 56 days in either a continuous (C) or rotational (R) silvopastoral system. Four 0.81 ha pastures were assigned to either the C or R system (two replications per treatment). Initial stocking rates for both treatments were 14.8 animals/ha which was reduced at the mid-point to 7.4 animals/ha. Forage quality, yield, and plant composition were measured weekly throughout the trial. Forage quality differences were determined by neutral detergent fiber (NDF), acid detergent fiber (ADF), and crude protein (CP) measurements. Forage composition was determined by separating material into four categories: grass, legume, weed and dead plant material. Tree response (diameter at breast height and height growth) was measured prior to and following the grazing period. No significant differences were observed for cattle average daily gain between treatments. Forage availability was higher (P > 0.05) for the R treatment. There were no differences for %NDF (P < 0.10) while %ADF was lower (P > 0.10) and %CP tended (P = 0.12) to be higher for R when compared to C. Rotational pastures had higher (P > 0.10) percentages of grass and legume with lower (P > 0.10) percentage dead material. There were no treatment differences (P < 0.10) for tree diameter at breast height. The average height growth for C was 1.67 m while R was 1.19 m which was only numerically different (P = 0.13). It is postulated that differences in height growth were due to increased water competition in R due to increased soil moisture loss by vegetative growth and transpiration.[PUBLICATION ABSTRACT]