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While total forage cover varied seasonally (Figures 36 & 37), regression analysis identified significant trends across the five-year study period. Total forage cover was significantly affected by both stocking rate and grazing management (Figures 38 & 39). Total forage cover declined at the two lower stocking rates in both grazing management systems while the highest stocking rate maintained total forage cover over the five years of the study.
Stand decline in the lowest stocking rate can be attributed to the accumulation of dead material in the sward and large patches of forage being smothered under the excess residue. The amount of dead residue present in low stocking rate pastures was significantly greater at low stocking rates at almost every observation date (Figures 40 & 41).
Total grass cover fluctuated from year to year but was very similar at the beginning and end of the study (Figures 42 & 43). Most of the reduction in grass cover occurred when legume cover reached its peak. The shift between grass and legume components is what allowed total forage cover to remain near constant at the higher stocking rates. Legume content of the pastures fluctuated much more widely than did the grasses (Figures 44 & 45), possibly due to greater sensitivity to weather conditions and the cyclic nature of red clover in natural reseeding situations.
Increasing stocking rate resulted in increased legume cover in both continuous and rotationally grazed pastures. Excessive grass competition at the lowest stocking rate resulted in a rapid decline in legume presence early in the study. Extremely dry conditions in 1999 brought legume content to its lowest level, but rapid recovery came in 2000 with favorable rainfall during the summer months. The earlier pattern of greater legume presence with increasing stocking rate was evident during the legume recovery in the final year of the study. Even with the annual variance in legume composition, there was a significant difference between continuous and rotational grazing in maintenance of legumes in the sward at all stocking rates except the lowest. When the trend lines are evaluated, there was only a slight decline in legume composition over the five-year period in rotationally grazed pastures while continuously grazed pastures exhibited a much more pronounced decline in legumes. The slopes of the regression lines for legume decline in continuous and rotational pastures were similar for 300 lb stocking rate but were significantly different at the three higher rates
Continuous grazing resulted in more exposed bare ground at the end of the five years compared to the beginning of the study, except at the 300 pound stocking rate. Accumulated dead material at the lowest stocking rate kept the soil well protected. Rotational grazing better protected the soil surface while maintaining less than ten percent bare ground at all stocking rates. Less exposed soil should enhance rainfall infiltration and reduce risk of runoff
The Missouri Agricultural Experiment Station is the research arm of the College of Agriculture, Food and Natural Resources at the University of Missouri-Columbia Site maintained by people at AgEBB | |||||||||||||||||||||||||||||||||||||
