Evapotranspiration of Cotton and Estimation Methods<sup>1</sup>

Namken, L. N.; Gerard, C. J.; Brown, R. G.

doi:10.2134/agronj1968.00021962006000010002x

Cited by 7 publications

(4 citation statements)

References 2 publications

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“…The March and August data are not presented, since the time intervals were not the same. The monthly water use follows the normal pattern for cotton (1,7). Water use begins to increase rapidly at about first bloom (mid-May) corresponding to a rapid increase in leaf area index.…”

Section: Monthly Distribution Of Water Usementioning

confidence: 77%

Water Use by Cotton From Low and Moderately Saline Static Water Tables¹

Namken¹,

Wiegand²,

Brown³

1969

Agronomy Journal

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A 4‐year lysimeter study was conducted to determine the contribution of low to moderately saline, shallow static water tables to the total water use and yield of cotton grown on deep, permeable soils. Water tables controlled at 91‐, 183‐, and 274‐cm depths contributed 54.4, 26.4, and 17.3% of the total water use under the high moisture treatment and 60.6, 48.9, and 39.2% under the low moisture treatment. Total water use consisted of soil profile depletion, rainfall, irrigations, and additions of water to maintain the water tables. Water uptake from the 274‐cm water table was strongly related to the salinity level (electrical conductivity of saturated soil extract, ECe) of the capillary (183‐ to 274‐cm) zone. Lint cotton yields were related to the total amount of water obtained from the table as well as to the salinity level of the capillary zone. Moderate salinity (ECe of 10 to 14 mmhos/cm) of the capillary zone reduced monthly and seasonal water use from the water tables as compared with low salinity (ECe of 2 to 3 mmhos/cm) conditions. The high moisture treatment delayed significant use of water from 183‐ and 274‐cm water tables until late in the season, when irrigations were discontinued and the upper soil profile dried.

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Section: Monthly Distribution Of Water Usementioning

confidence: 77%

Water Use by Cotton From Low and Moderately Saline Static Water Tables¹

Namken¹,

Wiegand²,

Brown³

1969

Agronomy Journal

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“…Even though the Ep/Eo ratio for cotton in 1968 reached l.O for only about 15 days, the soil water supply to plant roots became a limiting factor causing the decrease in relative Ep. Data of Namken et al (1968) for well-watered cotton plan;:s show that water evaporation from cotton can- opies continues at near potential rates throughout the season until the water supply becomes limiting. The main departure of the data points from the smoothed curve, fitted by eye in Fig.…”

Section: Plant Evaporationmentioning

confidence: 99%

Dryland Evaporative Flux in a Subhumid Climate: II. Plant Influences¹

Ritchie¹,

Burnett²

1971

Agronomy Journal

178

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Seasonal variation in three plant factors and in evaporation rates were determined for dryland cotton and grain sorghum in central Texas. Plant factors measured were fractional ground cover, dry matter production, and leaf area index (LAI). When an adequate supply of soil water was available in the rhizosphere, plant factors influenced evaporation rates during most of the first half of the groiwng season until a “threshold” canopy LAI was obtained. A threshold canopy LAI is defined as the minumum LAI necessary to obtain 90% of potential evaporation (Eo) from row crops when the soil evaporation (Es) is small. The threshold LAI was approximately 2.7 for both crops studied. After the threshold canopy LAI was obtained, evaporation was practically independent of plant factors and equal to Eo, as estimated from daily net radiation, until soil water movement to plant roots began to limit evaporation. Es strongly influenced the actual evaporation rates obtained when plant canopy LAIs were below 2.7, To evaluate the influence of plant factors on the resulting plant evaporation (Ep) independent of Es, it was necessary to attempt a rational separation of Es, and Ep. Es was assumed to be equal to the net radiation equivalent of evaporation below the plant canopy when the soil surface was wet. After the soil surface dried sufficiently to limit water movement to the surface, Es was estimated from the measured soil water content near the surface. Ep was estimated using the measured evaporation and Es. The ratio Ep/Eo was found to be related to the LAI according to the equation Ep/Eo = −0.21 + 0.70 LAI1/2, 0.1 ≤ LAI ≤ 2.7 This nonlinear relation indicates that Ep is larger per unit of leaf area for smaller plants than for larger plants with LAIs approaching 2.7. Sensible heat originating over partially dry surface soil between plant rows was a significant source of the total energy contributing to Ep The physiological stage of growth did not greatly influence the amount of energy used in evaporation as grain sorghum plants approached maturity when an adequate supply of soil water was available. The results imply a possibility for improving water‐use efficiency of dryland crops by using higher plant populations and closer row spacings to decrease Es if the soil water supply and seasonal rainfall is adequate to produce an economic yield.

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“…However, the LES may be more sensitive to air temperature than that of LEE, Sakuratani (1987) reports for well watered soybean crop grown in N-S rows. With the advance of crop growth the LES decreases (Gates and Hanks, 1967;Namken et al, 1968) as plants harvest most of the incoming radiation with the expansion of canopy area.…”

Section: Introductionmentioning

confidence: 99%

Comparisons of Moisture and Energy Balance Components as Influenced by Two Row Orientations of Soybean.

Baten

Kon

Matsuoka

1997

J. Agric. Meteorol.

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When a crop is grown in rows, the row direction influences the energy balance and moisture budget of the soil-canopy system of the crop. Attempts were made to compare energy balance and moisture budget of E-W row soybeans with those of N-S rows at partial cover during the summer of 1996. The energy balance and moisture budget were considered for the soil and canopy separately. Daily fluctuations and diurnal patterns of energy and water balance of field, soil and canopy were strongly influenced by roworientations.Average latent heat flux density (LE) observed in N-S row soybean field was 6.6% larger as compared to E-W row soybean field. Average ratios of -LE to net radiation (Rn) were found 0.85 and 0.87 for E-W and N-S rows, respectively. Soil heat flux (G) accounted for 14 to 20% of Rn for E-W rows and 6 to 9% for N-S rows. Soil surface net radiation (Rns) of E-W rows was about 25% larger than that of N-S rows. Latent heat flux from the soil (LES) was about 13% larger in E-W rows as compared to N-S rows. The -LES/Rns ratios often exceeded 1.0 in both the cases. The sensible heat flux from the soil showed a positive trend in both the cases indicating soil surface was absorbing convective heat. The -G/Rns ratios were found 0.41 and 0.26 for E-W and N-S rows, respectively. Average net radiation of E-W row canopy (Rns) was 20% smaller as compared to N-S row canopy. Latent heat flux from the E-W row canopy (LEe) was 19% smaller as compared to N-S row canopy. The -LES/Rns ratios were found 0.80 and 0.79 for E-W and N-S rows, respectively. Sensible heat flux from the canopy showed negative trends in both the cases. Results suggest that only field energy balance measurements would not provide sufficient information on how energy balances of the soil and canopy are partitioned.

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Evapotranspiration of Cotton and Estimation Methods¹

Cited by 7 publications

References 2 publications

Water Use by Cotton From Low and Moderately Saline Static Water Tables¹

Water Use by Cotton From Low and Moderately Saline Static Water Tables¹

Dryland Evaporative Flux in a Subhumid Climate: II. Plant Influences¹

Comparisons of Moisture and Energy Balance Components as Influenced by Two Row Orientations of Soybean.

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Evapotranspiration of Cotton and Estimation Methods1

Cited by 7 publications

References 2 publications

Water Use by Cotton From Low and Moderately Saline Static Water Tables1

Water Use by Cotton From Low and Moderately Saline Static Water Tables1

Dryland Evaporative Flux in a Subhumid Climate: II. Plant Influences1

Comparisons of Moisture and Energy Balance Components as Influenced by Two Row Orientations of Soybean.

Contact Info

Product

Resources

About

Evapotranspiration of Cotton and Estimation Methods¹

Water Use by Cotton From Low and Moderately Saline Static Water Tables¹

Water Use by Cotton From Low and Moderately Saline Static Water Tables¹

Dryland Evaporative Flux in a Subhumid Climate: II. Plant Influences¹