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Emergence Force of Cotton Seedlings as Influenced by Salinity¹

Soil crusting and salinity reduce emergence of seedlings and stands of many crops throughout the world. The force exerted by germinating plants such as cotton (Gossypium hirsutum L.) under stress due to salinity has not been determined. The purpose of these studies was to evaluate the force exerted by emerging cotton seedlings under different soil and solution salinities using a force transducer.

Emergence force of cotton seedlings was a curvilinear function of soil salinity. Each unit increase in soil salinity in the range of ECe (the electrical conductivity of the soil solution) of 4 to 17.0 mmhos/cm caused an average decrease of 23.5 g of emergence force. Emergence force of cotton seedlings was also a curvilinear function of the EC of the saline nutrient solutions. The force exerted by cotton seedlings was not significantly different when seedlings were grown in nutrient solutions having EC of 1.6 and 9 mmhos/cm. However, emergence force by cotton grown in saline solutions of 9 to about 30 mmhos/cm was a linear function of solution salinity expressed in mmhos/cm. Each unit increase in nutrient solution salinity caused a 20 g decrease in emergence force. In soils (Udic palenustalf) irrigated with saline water, emergence force would be a dynamic expression of the continually changing salinity and moisture conditions in the zone of the emerging seedling.

In the range of salinities of 1.6 to 17.3 mmhos/cm the time required for expression of maximum force ranged from 58 to 77 hours. In contrast each unit increase in salinity in the range of 17.3 to 29.7 mmhos/cm increased the time required for expression of maximum force by almost 13 hours.

Growth of hypocotyls which influence the force exerted by cotton seedlings was a function of solution salinity. Cross sectional areas of hypocotyls ranged from 0.13 to 0.04 cm². Emergence force appears to be an excellent expression of growth conditions or stress caused by salinity and possibly could be used to determine the salinity tolerance of emerging seedlings.

Key Words: Hypocotyl • Transducer • Soil crust • Gossypium hirsutum L.

² Technician and professor, Texas Agric. Exp. Stn., Texas A&M Univ. Agric. Res. and Ext. Ctr., Vernon, TX 76384.

Received for publication October 13, 1981.