Mineral Nutrition Characteristics of Warm-Season Grasses : I. Specific differences among several warmseason grasses in the variations of N, P and K content during growth period

Specific differences in the variations of growth and N, P and K content during growth period among Rhodesgrass (Chloris gayana), Dallisgrass (Paspalum dilatatum), Bahiagrass (Paspalum notatum), blue panicgrass (Panicum antidotale) and orchardgrass (Dactylis glomerata) grown under the same field conditions were studied as the first step to clarify the characteristics of warm-season grasses in mineral nutrition. 1. The warm-season grasses rapidly increaced plant height and dry matter yield above 20℃ and 25℃ of mean temperature, respectively, while orchardgrass was stunted when the mean temperature exceeded 25℃. Blue panicgrass showed a physiological disorder at about middle of August, probably due to the soil conditions. The highest dry matter yield of each grass was as follows ; Dallisgrass (1, 304g/m^2), Rhodesgrass (895g/m^2), Bahiagrass (832g/m^2), orchardgrass (374g/m^2) and blue panicgrass (297g/m^2). Rhodesgrass reached to the highest yield at the heading stage, while yields of Dallisgrass and Bahiagrass increased at a constant rate for about one month after the heading stage. 2. Although N concentration of each grass generally decreased in the similar manner with the progress of the growth, specific differences in N concentration were found in the following descending order ; orchardgrass>Dallisgrass=Eahiagrass=blue panicgrass>Rhodesgrass until the end of the growth. Specific differences in the largest amount of N contained was found as follows ; Dallisgrass (9.75g/m^2)>Rhodesgrass (8.72g/m^2), Bahiagrass (8.60g/m^2)>orchardgrass (6.64g/m^2)>>blue panicgrass (3.27g/m^2). Dallisgrass, Rhodesgrass and orchardgrass reached to the highest N content about one month earlier than Bahiagrass and blue panicgrass. 3. Phosphorus concentration of Rhodesgrass, Bahiagrass and Dallisgrass decreased gradually with the progress of the growth, but blue panicgrass showed the highest P concentration after the end of September. Specific differences in P concentration were found as blue panicgrass>>orchardgrass>Rhodesgrass>Dallisgrass=Bahiagrass until each grass reached to the highest dry matter yield. The largest amount of P contained in each grass was as follows ; Rhodesgrass (2.88g/m^2)>Dallisgrass (2.61g/m^2)>Bahiagrass (1.96g/M^2), blue panicgrass (1.91g/m^2)>orchardgrass (1.47g/M^2). Phosphorus conten of Rhodesgrass rapidly increased in the vegetative stage as compared with other grasses. 4. Potassium concentration of the four warm-season grasses decreased with the progress of the growth, but that of orchardgrass increased from the end of September. Specific differences in K concentration was found as orchardgrass>Dallisgrass>blue panicgrass>Bahiagrass>Rhodesgrass until the middle of August. The largest amount of K in each grass was found in the order of Dallisgrass (23.2g/m^2)>Bahiagrass (15.8g/m^2)>orchardgrass (11.6g/m^2), Rhodesgrass (10.6g/m^2)>blue panicgrass (5.1g/m^2). Potassium content of Dallisgrass rapidly increased in the vegetative stage as compared with other grasses. The specific differences were discussed in reference to the characteristics of each grass in N, P, or K absorption.