Author

James K. Wolf

Date of Award:

1977

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Advisor/Chair:

R. John Hanks

Abstract

A model was developed to predict the effects of soil salinity on crop growth. The model makes three major assumptions: 1) Relative yield for a growing season is directly related to the ratio of actual and potential transpiration. 2) Water uptake by plants is in response to the water potential gradient between the plant roots and the surrounding soil. 3) The effects of the soil salinity on crop growth is solely due to the affect of osmotic potential in decreasing the water potential. Minor assumptions also included are concerned with the plant growth cover, plant root growth, and the separation of E and T from ET.

The model's ability to predict crop growth under various irrigation amounts and frequency of application, irrigation water quality, and initial soil salinity was compared with field measured results.

The model predicted reductions of crop yield as irrigation rates were decreased which agreed closely to field measurements where salinity was held constant. Increasing salinity of the irrigation water from the normal (EC=0.5 mmhos/cm) to the rate corresponding to the value estimated for the lower Colorado River in 2000 A.D. (EC=2.0 mmhos/cm), was predicted to have a very slight effect on yield for one years use. This agreed with the field measurements.

It was found that the model under predicted the effects of high initial soil salinity (simulating many years of salt buildup) on yield. These results indicated that high initial soil salinity for corn had more effect on crop growth than just the osmotic effect for the field situation studied.

Comments

A model was developed to predict the effects of soil salinity on crop growth. The model makes three major assumptions: 1) Relative yield for a growing season is directly related to the ratio of actual and potential transpiration. 2) Water uptake by plants is in response to the water potential gradient between the plant roots and the surrounding soil. 3) The effects of the soil salinity on crop growth is solely due to the affect of osmotic potential in decreasing the water potential. Minor assumptions also included are concerned with the plant growth cover, plant root growth, and the separation of E and T from ET.

The model's ability to predict crop growth under various irrigation amounts and frequency of application, irrigation water quality, and initial soil salinity was compared with field measured results.

The model predicted reductions of crop yield as irrigation rates were decreased which agreed closely to field measurements where salinity was held constant. Increasing salinity of the irrigation water from the normal (EC=0.5 mmhos/cm) to the rate corresponding to the value estimated for the lower Colorado River in 2000 A.D. (EC=2.0 mmhos/cm), was predicted to have a very slight effect on yield for one years use. This agreed with the field measurements.

It was found that the model under predicted the effects of high initial soil salinity (simulating many years of salt buildup) on yield. These results indicated that high initial soil salinity for corn had more effect on crop growth than just the osmotic effect for the field situation studied.

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