Studies on the Root Function of Forage Crops : II. Effect of cutting on the sod-binding of the orchrd grass sward

Abstract

The influence of three cutting treatments (one, four and six times a year) on the sod-binding of the orchard grass sward was studied. The sward was established in 1957 and the total green yields of 1C, 4C, and 6C in 1959 were 130.1, 207.3, and 192.1 kg. per are respectively. (Table 1) By the autumn in 1959 the frequently cut sward had considerably more plants and tillers per unit area. (Table 2). As a result of these changes in plant density, the root weight of the sward especially in the surface soil was increased (Table 3) and there was observed the sod-dinding in the surface soil by increasing the cutting frequency. (Fig. 2) But respiration and NO3-N absorption of roots in the surface soil decreased by increasing the cutting frequency. (Table 4) The physical condition of the soil was changed by the sod-binding. Air per cent in the surface soil decreased and water per cent increased, so soil pore-space in the surface soil had a tendency to decrease as the sod-bound formed. (Table 5) These changes in physical conditions of the surface soil caused the retard of the water infiltration into the soil (Table 6) and of the root penetration of some reseeded legumes. (Table 7) These unfavorable soil conditions such as the increase of soil compactness and the decrease of soil aeration were assumed main causes of decrease of the sward productivity. In August, the soil temperature of the sward was measured. Soil temperature of 6C was higher than 4C at 2 cm in depth but at 5 and 10 cm in depth, 4C was higher than 6C conversely. It was assumed that the sod-binding had a mulching effect. (Fig. 1) It was assumed that two following factors concenrned with the sod-binding. The one was the increase of plant density accompanied with the increase of the root mass in the surface soil and the other was the delay of the decomposition of dead root materials owing to the unfavorable circumstances of the soil physical conditions.