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The Texas Water Resources Institute, a unit of the Texas Agricultural Experiment Station and Texas Cooperative Extension, and member of the National Institutes for Water Resources, provides leadership to stimulate priority research and Extension educational programs in water resources within the Texas A&M University System and throughout Texas.

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Volume 4, Number 2

Unknown author (Texas Water Resources Institute, NaN)

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URI: http://handle.tamu.edu/1969.1/85761

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Effects of Salinity and Specific Ions on Seedling Emergence and Growth of Onions

Miyamoto, S.; Martinez, I.; Niu, G. (Texas Water Resources Institute, August 2008)

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Abstract:

The concentrate from nanofiltration is usually enriched with divalent ions, such as Ca, Mg and SO4. Since divalent ions are less hazardous to soils and plants, it was hypothesized that the disposal of nanofiltration concentrate to irrigation water may not be deleterious, especially for growing crops sensitive to specific effects of Na and/or Cl. This study examined the above hypothesis by observing the effect of salinity and ion composition of irrigation water on seedling emergence, survival and growth of onions. Onions are an important winter crop grown in the Rio Grande Valleys, and are regarded as being sensitive to Cl ions. Two soil types (Harkey silt loam and Bluepoint loamy sand) were used for a greenhouse experiment involving two onion cultivars ‘BR-1’ and ‘Chaco’. Harkey silt loam had three levels of initial soil salinity (3.9, 2.2 and 0.6 dS m-1). They were placed in pots, seeded and irrigated for 4 ½ months using nine types of saline solutions. The first four solutions had four levels of salinity: 1.0, 1.8, 3.7 and 5.2 dS m-1 (or 630, 1200, 2500 and 3700 ppm) at a constant ionic ratio of 1:1 for Na: Ca + Mg, and Cl: SO4, and other solutions had three levels of ionic concentration ratios; 3:1, 1:1, and 1:3 at fixed levels of salinity, either 20 or 40 me L-1. The last solution was prepared by adding Ca and SO4 at 20 me L-1 to the 2.2 dS m-1 solution. Seedling emergence, survival and growth were measured along with soil salinity, and Na Ca and Cl contents of the plant tissue. Results have shown that seedling emergence and survival were affected by watering methods and soil types, especially by the initial soil salinity levels, besides salinity of the irrigation solutions. In surface-irrigated loamy sand, seedling emergence and survival were excellent, regardless of the saline solutions used. In surface-irrigated silt loam, seedling emergence was low (< 20%), presumably due to soil crusting. In subirrigated silt loam, seedling emergence and survival were reduced by increasing initial soil salinity and salinity of the irrigation solutions, but not by the ion composition. Seedling growth was also reduced by increasing salinity and Cl/SO4 ratios when Cl concentration exceeded 10 me L-1 in irrigation water. The addition of Ca and SO4 to an irrigation solution (2.2 dS m-1) reduced seedling growth. The tissue Na and, to some extent, Cl concentration increased with increasing Na/(Ca + Mg) ratio in irrigation water. A similar trend was found for the Cl to SO4 ratios, while tissue Ca concentrations remained relatively stable. The Cl concentration of the plant top was higher than that in the roots, when its concentration in the irrigation solution exceeded approximately 10 me L-1. Although onions were shown to accumulate Cl ions in plant top, the deleterious effect of Cl seems to appear after seedling growth is first curtailed by salinity. The establishment of onion crops are controlled largely by soil salinity, soil types and management practices rather than ionic composition. The application of nanofiltration concentrate to irrigation water inevitably increases salinity, and for this reason, it is unlikely to be beneficial for onion crop production under the prevailing furrow-irrigated conditions of the Rio Grande Valleys.

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http://handle.tamu.edu/1969.1/85760

Files in this item: 1

An Interindustry Model of El Paso and Hudspeth Counties, Texas

Adams, J. W.; Jones, L. L.; Beattie, B. R.; Coffman, W. S. (Texas Water Resources Institute, April 1976)

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URI: http://hdl.handle.net/1969.1/6295

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A Cross-Sectional Investigation of the Determinants of Urban Residential Water Demand in the United States, 1960 and 1970

Beattie, B. R.; Foster, H.S. (Texas Water Resources Institute, May 1978)

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Abstract:

This research was undertaken to specify and estimate a model relating household demand for urban water to its principal determinants. Four specific tasks were accomplished: 1. An appropriate economic demand model for urban-residential water supplies was postulated. An improved specification of the rainfall variable was developed to account for turf maintenance demand. The price of water was specified in exponential form making its elasticity price dependent. 2. Parameters of the model were estimated based on pooled data representing a cross-section of U.S. cities. 3. Parameters were estimated for a regionalized version of the model by incorporating sets of dummy variables. Tests for statistical differences among key economic coefficients were made to ascertain regional differences, if any. 4. Parameters were estimated for a model disaggregated by size-of-city categories again by incorporating dummy variable sets. Tests for statistical differences among key economic coefficients were made to ascertain differences among size-of-city categories, if any. The demand models were fitted using 1960 and 1970 data and ordinary least squares regression techniques. Explanatory variables included price, income, precipitation (during the defined growing season) and number of residents per meter in addition to sets of dummy variables on the constant factor and price and income coefficients. The results suggest that size of city is not statistically significant in determining the residential demand for urban water. However, regional differences are significant. For the regional model, price, income, and residents per meter were significant at the 1 percent level for the 1960 data; price and precipitation were significant at the 1 percent level for the 1970 data. R2-values were .74 and .71 for the 1960 and 1970 data, respectively. Income and price elasticities are presented for all regions at the mean price level and for one standard deviation above and below this price level. Mean price level elasticities ranged between -.30 and -.82 and between -.33 and -.67 for the 1960 and 1970 data, respectively, suggesting an inelastic residential water demand at present price levels. The elasticity estimates derived from the regional coefficients of this study compare favorably with those of earlier more micro-level analyses.

URI:

http://hdl.handle.net/1969.1/6293

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