Abstract
Abstract. A five-year field study (2007-2011) of irrigated alfalfa production with a limited water supply was conducted in southwest Kansas with two years of above-average precipitation, one year of average precipitation, and two years of below-average precipitation. The irrigation treatments were designed to reflect the declining ability of the aquifer to supply water for irrigation, the constraints of water rights, and irrigation management that either distributed water over the growing season or withheld water during the most stressful part of the growing season. Dry matter yields, averaged over irrigation treatments, declined from 1.68 kg m-2 in the first year to 0.41 kg m-2 in the final year because stored soil water contributed to crop evapotranspiration (ETc) in the first year, but precipitation could not replenish soil water in the following years, and stand densities declined over time. Annual yields, averaged over years, declined from 1.53 kg m-2 with 610 mm of irrigation to 0.43 kg m-2 for rainfed production. Annual yields were the same when irrigation was distributed over the growing season or withheld between the second and third cuttings. Crop productivity (water use efficiency) and plant stand decreased significantly as irrigation decreased and from the first through the final year of production. A linear regression of alfalfa dry matter yields with respect to evapotranspiration (ETc) produced an R2 equal to 0.90. Yield response to irrigation was influenced by irrigation amount, precipitation, and the depletion of stored soil water from the beginning to ending years. Yields were highest in the first year, and the marginal yields decreased as irrigation decreased that year. Yield response to irrigation was nearly linear during the second through fourth years and linear during the fifth year with drought, indicating that alfalfa efficiently utilized irrigation and precipitation. Regression of yield-irrigation data from the middle three years of this study overlapped the results from a ten-year field study conducted at the same location from 1921 through 1930, demonstrating that similar alfalfa dry matter was produced with presumably similar atmospheric energy. Because the same irrigation treatment was in the same plot location for all years, available soil water (ASW) at the end of the previous growing season influenced the next year’s starting soil water content (θv). All plant-available water was depleted during the first growing season to a depth of at least 2.4 m, and it was partially restored in only one other dormant season. In all years, θv diminished to a value of 0.1 in the rainfed treatment, which was less than 0.15, the assumed wilting point for corn, grain sorghum, and sunflower in this soil. These results can be used to evaluate the economic viability of alfalfa production compared with other annual crops where limited water supplies lead to crop water stress.
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Claims 12
Claim · model-written summary
Mean dry matter yield declined from first to final year.
- Taxon
- Alfalfa
Medicago sativat0 - Outcome
- Dry matter yieldse0
- Direction
- declinede0
- Value
- 1.68 kg m-2e0
- Qualifier
- 0.41 kg m-2 in the final yeare0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Dry matter yields, averaged over irrigation treatments, declined from 1.68 kg m-2 in the first year to 0.41 kg m-2 in the final year”
t0“Alfalfa”
Claim · model-written summary
Annual yield declined from 1.53 under irrigation to 0.43 kg m-2 rainfed.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- 610Â mm of irrigatione0
- Outcome
- Annual yieldse0
- Direction
- declinede0
- Value
- 1.53 kg m-2e0
- Qualifier
- 0.43 kg m-2e0
- Comparator
- rainfed productione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Annual yields, averaged over years, declined from 1.53 kg m-2 with 610 mm of irrigation to 0.43 kg m-2 for rainfed production”
t0“Alfalfa”
Claim · model-written summary
Annual yields were equal under distributed and withheld irrigation.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- irrigation was distributed over the growing seasone0
- Outcome
- Annual yieldse0
- Direction
- the samee0
- Comparator
- withheld between the second and third cuttingse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Annual yields were the same when irrigation was distributed over the growing season or withheld between the second and third cuttings”
t0“Alfalfa”
Claim · model-written summary
Water use efficiency declined as irrigation decreased and over time.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- irrigatione0
- Outcome
- water use efficiencye0
- Direction
- decreasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Crop productivity (water use efficiency) and plant stand decreased significantly as irrigation decreased and from the first through the final year of production”
t0“Alfalfa”
Claim · model-written summary
Plant stand declined as irrigation decreased and over time.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- irrigatione0
- Outcome
- plant stande0
- Direction
- decreasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Crop productivity (water use efficiency) and plant stand decreased significantly as irrigation decreased and from the first through the final year of production”
t0“Alfalfa”
Claim · model-written summary
Regression of yield on evapotranspiration gave R2 of 0.90.
- Taxon
- alfalfaMedicago sativae0
- Outcome
- dry matter yieldse0
- Value
- R2 equal to 0.90e0
- Qualifier
- evapotranspiration (ETc)e0
Not reportedCompoundTreatmentComparatorSettingDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A linear regression of alfalfa dry matter yields with respect to evapotranspiration (ETc) produced an R2 equal to 0.90”
Claim · model-written summary
Yield response was nearly linear in years two through four and linear in year five.
- Taxon
- AlfalfaMedicago sativat0
- Outcome
- Yield response to irrigatione0
- Qualifier
- during the second through fourth years and linear during the fifth year with droughte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Yield response to irrigation was nearly linear during the second through fourth years and linear during the fifth year with drought”
t0“Alfalfa”
Claim · model-written summary
Middle-year yield–irrigation regressions overlapped an earlier study at the same location.
- Taxon
- AlfalfaMedicago sativat0
- Outcome
- Regression of yield-irrigation datae0
- Direction
- overlappede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Regression of yield-irrigation data from the middle three years of this study overlapped the results from a ten-year field study conducted at the same location from 1921 through 1930”
t0“Alfalfa”
Claim · model-written summary
Previous season water availability influenced starting soil water.
- Taxon
- AlfalfaMedicago sativat0
- Outcome
- starting soil water content (θv)e0
- Qualifier
- available soil water (ASW) at the end of the previous growing seasone0
Not reportedSettingDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“available soil water (ASW) at the end of the previous growing season influenced the next year’s starting soil water content (θv)”
t0“Alfalfa”
Claim · model-written summary
Plant-available water was depleted to at least 2.4 m in the first season.
- Taxon
- AlfalfaMedicago sativat0
- Outcome
- plant-available watere0
- Direction
- depletede0
- Value
- at least 2.4 me0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“All plant-available water was depleted during the first growing season to a depth of at least 2.4 m”
t0“Alfalfa”
Claim · model-written summary
Plant-available water was partially restored in only one dormant season.
- Taxon
- AlfalfaMedicago sativat0
- Outcome
- plant-available watere1
- Direction
- partially restorede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“it was partially restored in only one other dormant season”
e1“All plant-available water was depleted”
t0“Alfalfa”
Claim · model-written summary
Rainfed soil water content fell to 0.1 in all years.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In all years, θv diminished to a value of 0.1 in the rainfed treatment”
t0“Alfalfa”
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