Interrelationships of Irrigation Frequency, Urea Nitrogen, and Gypsum on Forage Sorghum Growth on a Saline Sodic Clay Soil1
- M. A. Mustafa and
- E. A. Abdelmagid2
Two field experiments were conducted in June, 1978, and April, 1979, at the Khartoum University Farm, Sudan, to study the effect of irrigation frequency, urea-nitrogen, and gypsum on the yield of forage sorghum (Sorghum vulgare L.) grown on a semi-arid, salinesodic clay soil. Each experiment had four nitrogen levels: 0N, 1N, 2N, and 3N (1N = 43.8 kg N/ha) applied as urea; three irrigation frequencies: 7, 10, and 15 days; and zero or 11.9 tonnes/ha gypsum, each replicated thrice in a split-split plot design. The seasonal quantity of water applied was the same for all frequencies of irrigation and was slightly higher than evaporation from a U.S. class A pan.
The two seasons data consistently showed that dry matter yield of the first cuts of forage sorghum increased significantly with increase in N-level, with decrease in irrigation interval, and with gypsum application. Decreased irrigation frequency had greater effect than 3N fertilization. The benefits from gypsum application were low (5%) at the 7-day irrigation interval. Dry matter yields were increased from 1.84 to 6.12 tonnes/ha in 1978 and from 3.20 to 7.23 tonnes/ha in 1979, by irrigating every 7 days instead of 15 days, application of 3N and 11.9 tonnes/ha gypsum.
Plant height and leaf area index increased with N fertilization, with gypsum and with reduction of irrigation interval from 15 to 7 days, whereas germination percentage was significantly increased by gypsum only. Dry matter yield significantly correlated (P = 0.01) with leaf area index and plant height but not with germination percentage. Multiple regression analysis showed that the first two growth attributes accounted for about 87% of the variability of yield. The dry matter yields of the second cuts were similarly affected by treatments but were about one-half to one-third those of the first cuts in 1978 and 1979 seasons, respectively.
For the two seasons the average seasonal water-use was about 1.02 times that of the U.S. class A pan evaporation. Water-use efficiency increased from 15.6 to 43.9 kg/ha-cm in 1978 and from 19.1 to 51.2 kg/ha-cm in 1979, by irrigating every 7 days instead of 15 days, and applying 3N urea and 11.9 tonnes/ha gypsum.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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