Alfalfa Water Use Research Articles

Hay Yield and Water Use Efficiency of Alfalfa under Different Irrigation and Fungicide Regimes in a Semiarid Climate

Alfalfa is one of the most nutritive and high-yielding forage legumes planted in rotation with cereal crops across the United States. Under semiarid and arid climates with limited water resources, sustainable management of the available resources is required. The objective of this study was to investigate the effect of different irrigation regimes and fungicide applications on alfalfa in the high desert region of the Colorado Plateau of the U.S. Field experiments were conducted during the 2012–2014 period. Alfalfa was planted in fall 2012, uniformly irrigated for crop establishment and subjected to seven different irrigation regimes after the first cut in spring 2013. Alfalfa was treated by fungicide application and was harvested at 10% blooming. The maximum amounts of applied water were 350, 300, 208, and 312 mm, respectively, during the first, second, third, and fourth regrowth cycles in 2013, and 373, 282, 198, and 246 mm in 2014 for the respective regrowth cycles in 2014; the seasonal applied irrigation amount varied from 711 to 1171 mm in 2013 and from 328 to 1100 mm in 2014. The results showed non-significant effect of fungicide application on the forage yield. Alfalfa forage yield was significantly affected by the irrigation regimes and showed a third order polynomial relationship with the applied irrigation amounts during each regrowth cycle and on seasonal scale. Forage yield decreased from the first cut to the fourth cut and the annual forage varied from 10.6 to 25.7 Mg/ha for the treated alfalfa and from 11.5 to 25.6 Mg/ha for the non-treated alfalfa. Forage yield at each cut accounted for 39.6, 24.2, 17.6, and 18.6% of the 2013 season forage yield and 31.4, 23.8, 21.6, and 23.2% of the 2014 season forage yield, for the first, second, third, and fourth cut, respectively. Alfalfa water use efficiency varied from 0.06 to 3.3 kg/m3. The relationships developed in this study could be used by forage growers, crop consultants, and project managers for decision making and planning to improve the productivity of water under the semiarid and arid climate of New Mexico and the surrounding regions.

The Dynamic Yield Response Factor of Alfalfa Improves the Accuracy of Dual Crop Coefficient Approach under Water and Salt Stress

The accurate quantification of crop water use or evapotranspiration (ET) under water and salt stress is needed for efficient water management and precision irrigation in water scarce regions. However, few studies were examined on alfalfa water use and its components under water and salt stress. We carried out two field experiments to quantify alfalfa water use through setting up different water and salt gradients, including two irrigation levels (full and deficit irrigation) and four soil salinity levels (0, 2‰, 4‰ and 6‰ salt of mass ratio) in an arid region of Northwest China. Electrical conductivity of soil saturation extract (ECe), soil water content (SWC), leaf area index (LAI) and soil evaporation (E) were measured. The SIMDualKc model, which uses the FAO56 dual Kc approach, was calibrated and validated using measured SWC and E. Model results show a good agreement between observed and simulated SWC and E without stress. The depletion fraction for no stress (p) and the percent yield reduction per unit increase in soil salinity (b) were 0.50 and 6.0%/(dS m−1), respectively, slightly lower than those of FAO-56 (0.55 and 7.3%/(dS m−1)). The difference indicates that alfalfa has a lower capacity of water use but a greater tolerance to salt stress after soil salinity reached its sensitivity threshold in the arid region. The model performed a reduced accuracy under water and salt stress and the differences tended to increase as stress increased, which was partly attributed to constant yield response factor (Ky) under different soil water and salt stress. The key parameter Ky dynamically increased with the increased degree of stress. Compared to constant Ky, the simulations of SWC and E showed improved accuracy with dynamic Ky. These results suggested that the response and acclimation of alfalfa to stress might be incorporated into the dual Kc model through the diversity of Ky.

Alfalfa Water Use and Yield under Different Sprinkler Irrigation Regimes in North Arid Regions of China

Alfalfa (Medicago sativa) is one of the major crops grown in Northern China in recent years, however, the current serious water shortage conditions present a challenge to the growth of this crop, especially if efficient use of water is considered in forage production for sustainability. This study aimed to evaluate alfalfa productivity and water use efficiency (WUE) under different sprinkler irrigation levels. This experiment was conducted at Shiyanghe Experimental Station for Water-Saving in Agriculture and Ecology of China Agricultural University in Wuwei, Gansu, China, over a period of two years. There were three irrigation treatments: A1: 100% measured evapotranspiration (ETc) of alfalfa; A2: irrigation amount was 66% of A1; A3: irrigation amount was 33% of A1; and a control of A4: no irrigation during the growing season. A randomized block design with three replications were applied. The results showed that the ETc and forage yield of alfalfa decreased, while WUE and crude protein (CP) increased with the decreasing irrigation amounts. The seasonal average ETc and yield ranged from 412 mm to 809 mm and from 11,577 to 18,636 kg/ha, respectively, under different irrigation levels. The highest yields were obtained from the first growth period in all treatments in both years, due to the winter irrigation and the longest growth period. Alfalfa grown under lesser irrigation treatment conditions had higher variability in ETc and yield, mainly due to the variability in the amount of rainfall during the growth period. The seasonal average WUE of treatments ranged from 22.78 to 26.84 kg/(mm·ha), and the highest WUE was obtained at the first growth period, regardless of treatments. Seasonal average CP content ranged from 18.99% to 22.99%. A significant linear relationship was found between yield and ETc or irrigation amount, and the fitting results varied between growth periods and years. The present results also implied that winter irrigation provided the space for saving water and should be applied at the end of each growing season to fill the soil profile, and to maintain a greater yield in the next growing season. During the growing season, more irrigation should be concentrated in the early growth period, especially in the second growth period.

Temporal dynamics of alfalfa water use efficiency under hyper arid conditions of Saudi Arabia

A field study was carried out to investigate the seasonal variations in alfalfa (Medicago sativa L.) water use efficiency (WUE) using Eddy Covariance (EC) measured CO2 and H2O fluxes, aiming at optimizing the use of irrigation water under hyper arid conditions. The EC system used for this study was installed on a center pivot-irrigated 50 ha alfalfa field. Results revealed that the net EC estimated CO2 uptake ranged from 65,00 kg ha−1 (in winter) to 21,500 kg ha−1 (in summer). While, H2O flux was 4,147 m3 ha−1 (in winter) and 20,157 m3 ha−1 (in summer). This resulted in an estimated alfalfa WUE of 1.57 and 1.07 kg m−3 for winter and summer seasons, respectively. However, the actual WUE of harvested alfalfa was calculated at 0.70 and 0.71 kg m−3 for winter and summer, respectively. Therefore, attaining an actual crop WUE of 33–55% lower than the EC measurement (i.e. more water losses were due to leaching and deep-percolation processes, as the EC system could only estimate evapotranspiration over agricultural fields) emphasizes the need of precision irrigation practices, which will enable farmers to apply irrigation water and agrochemicals more precisely and site-specifically to match soil and plant status and needs.

Alfalfa Water Use and Crop Coefficients across the Watershed: From Theory to Practice

In this study, remote sensing technology and crop production functions were used to compare the theoretical crop coefficient (Kc) and the theoretically optimal or potential crop evapotranspiration (ET) with actual ET for 751 alfalfa fields in the Lower Rio Grande Valley, New Mexico. Results of the remote sensing showed that, although potential alfalfa water use for the year 2008 was 1,451 mm, actual water use at the field level ranged from 386 to 1,241 mm with an average ET of 901 mm for the growing season. Average ET was also calculated using the average yield and published crop production functions. The average ET estimated from average yield using two different crop production functions was between 975–979 mm. Reasons for field-level ET and crop coefficient variability include current irrigation methods and technology, lack of knowledge of irrigation scheduling, limited water supply, interference of harvesting schedule with the irrigation, cultural practices, and economic factors. The results of the study have implications on water rights adjudication and economic return from alfalfa production. The results also reflect the potential for improvement in agricultural productivity and economic return by changing irrigation techniques and agronomic practices.

Water table contribution to alfalfa water use in different environments of the Argentine Pampas

En la Region Pampeana Argentina, se considera a la capa freatica como una importante fuente de agua para la alfalfa, aun cuando su aporte no fue previamente cuantificado. El objetivo de este estudio fue estimar la contribucion de la napa freatica al consumo de la alfalfa en diferentes ambientes, usando un metodo indirecto que utiliza mediciones de la eficiencia en el uso del agua. Los datos fueron obtenidos de cuatro anos de experimentos, en cuatro localidades: Anguil,Rafaela, General Villegas y Manfredi. La contribucion de la capa freatica fue estimada considerando la eficiencia en el uso del agua del cultivo, y el consumo de agua de las capas superiores de suelo, (recarga dependiente de lluvias). Se asumio una contribucion de la capa freatica al consumo del cultivo cuando la relacion materia seca/consumo de agua de las capas superiores de suelo supero un valor umbral de eficiencia en el uso del agua. Este aporte vario entre localidades,entre 15 y 25% del agua consumida por el cultivo, y no estuvo relacionado con la profundidad de la capa freatica. Se establecio una relacion exponencial entre la contribucion estacional de la capa freatica y la precipitacion efectiva estacional.

Alfalfa water use pinpointed in saline, shallow water tables of Imperial Valley

Although alfalfa is the dominant water user in the Imperial Valley and is planted on 40% of its irrigated acreage, data is incomplete regarding its water use under the most common growing conditions: moderately saline, clay soils with a relatively shallow, moderately saline water table. In a study from 1996 through 1998, we determined the seasonal variation in the alfalfa crop coefficient (Kc), based on measurements of applied water and soil-moisture depletion, and the contribution from the water table aquifer. Using chloride mass-balance methods, we estimated that the shallow water table contributed approximately 12% of the total applied water during the study, of which just over 8% occurred during the first year. Correcting the values for water table contributions (WTC) to crop water use removed the increasing trend in values during the study and resulted in an overall study crop coefficient of 0.84. The decrease in WTC was the result of a doubling in soil salinity to 12 deciSiemens per meter at the 3- to 4-feet-depth interval by the second year. For moderately saline growing conditions in the Imperial Valley, the alfalfa crop coefficient is smaller than elsewhere in the southwestern states, where values closer to one are common.

Canopy CO 2 assimilation, energy balance, and water use efficiency of an alfalfa crop before and after cutting

Canopy photosynthesis, energy balance and evapotranspiration (ET), and water use efficiency of an alfalfa ( Medicago sativa L.) crop were followed by measuring the above-canopy fluxes with the Bowen ratio/energy balance/CO 2 gradient technique and correcting for CO 2 released by the soil and roots via respiration. Measurements were taken late in the season, just before the last cutting, after cutting, during regrowth, and during the initial senescence phase near the end of autumn. Before cutting, canopy photosynthesis rate was similar to those for other high yielding crop species and ET was very close to reference ET rate, with most of the energy for evaporation coming from net radiation and a small part from sensible heat. Net canopy CO 2 assimilation rate ( A c) reached 1.7 mg (39 μmol) CO 2 m −2 s −1 around noon on sunny days and up to 2.4 mg (55 μmol) CO 2 m −2 s −1 in periods between clouds on a windy and relatively cool day. A c increased with increase in photosynthetic active radiation up to 1700 μmol m −2 s −1 with no sign of light saturation. Immediately after cutting, ET was reduced markedly; A c was reduced even more drastically but remained positive. Energy balance changed so that only a minor fraction of the net radiation was used for ET, and the major part was dissipated as sensible heat and as storage heat flux into the soil. Evapotranspiration dropped to about 1 mm per day, but started to increase after cutting over a period of about 2 weeks. A c also increased and reached 84% of pre-cutting value about 3 weeks after cutting. Seven diurnal curves of A c, ET, and parameters associated with energy fluxes are presented, spanning pre-cutting, immediately after cutting, regrowth and the start of senescence. Before cutting, water use efficiency of the alfalfa normalized for the evaporative demand was between 49.1 and 52.8 g CO 2 m −2 per day (approximately 10.5–11.3 g dry matter m −2 per day), declined to 7.5 g CO 2 m −2 per day after cutting, but increased afterwards continuously, reaching 46.3 g m −2 per day 3 weeks later, before declining under less favorable growing conditions as the end of autumn approached. Under favorable conditions, alfalfa water use efficiency appears to be as high as most other crops when the cost in assimilates for symbiotic nitrogen fixation and mycorrhizal fungi, larger proportion of root biomass, and higher protein content are taken into account. Its reputation as a water spender is not deserved.

Alfalfa Yield and Stand Response to Irrigation Termination in an Arid Environment

AbstractAlfalfa (Medicago sativa L.) irrigation is often withheld as a water conservation measure in arid regions. The objective of this research was to test the hypothesis that alfalfa yields and stands can be permanently damaged by withholding irrigation water in arid environments. Irrigation termination studies were conducted on a Superstition sand (sandy, mixed, hyperthermic Typic Calciorthid; 95% sand) in Yuma, AZ, and on a Casa Grande sandy loam [coarse‐loamy, mixed (calcareous), hyperthermic Typic Natrargid (reclaimed)] at Maricopa, AZ. Irrigations were terminated in the summer (July through October) and winter (November through February) in Yuma and in the summer (August through September) and summer, fall, and winter (August through mid‐March) in Maricopa. Summer irrigation termination at the Yuma site reduced stand from 43 to 16 plants m−2 and reduced hay yield from 1.50 to 0.52 Mg ha−1 per cutting after irrigation was resumed. Irrigation termination at the Maricopa site was not detrimental to stands, although hay yields per cutting were depressed from 2.90 to 2.52 Mg ha−1 following the second cycle of summer irrigation termination and from 3.10 to 2A3 Mg ha−1 following the second cycle of summer through winter irrigation termination. Winter irrigation termination at Yuma had no residual effect on yield or stand. Alfalfa water use was reduced by irrigation termination at Maricopa, even after irrigation was resumed. Total nonstructural carbohydrates in the roots were not consistently higher or lower than the control during irrigation termination. Termination of alfalfa irrigation as a water‐conserving measure is not always advisable in arid environments due to the possibility of permanent crop damage.

Root Distribution and Water Use Efficiency of Alfalfa as Influenced by Depth of Irrigation1

AbstractRoot distribution of several crop plants is known to be affected by different patterns of soil moisture. In alfalfa (Medicago sativa L.), however, such results have not been consistently obtained under field conditions. Our objective was to determine the effect of different irrigation depths on alfalfa water use efficiency, water extraction patterns, and root distribution under greenhouse conditions where examination of the entire root systems was possible. ‘Cimmaron’ alfalfa was planted in polyvinylchloride (PVC) containers (120 ✕ 30 cm) filled uniformly with a Leeper fine (fine, montmorillonitic, nonacid, thermic Vertic Haplaquept) sandy loam top soil. Irrigation treatments included: watering to saturate the soil one‐third of the whole root depth, watering to saturate the soil two‐thirds of the whole root depth, and no irrigation. Irrigation was applied when available soil moisture content within the root zone reached 35 % (−2.5 bars soil matric potential). The parameters studied included root distribution pattern, total root growth, water extraction pattern, and water use efficiency. The efficiency of water use was higher in deeply irrigated treatments than in shallow irrigated treatments during June and July (a period of high evapotranspirational demand), but it was not different during September to November. Depth of irrigation did not affect total root production, but it did affect root distribution at the irrigation zone. Deeply irrigated plants produced slightly more roots in the lower depths than shallow irrigated plants. Root production of nonirrigated alfalfa was low under the high evaporational demand conditions which occurred during June and July, but was highest among all treatments during the September to November growing period. Root:shoot ratios of 0.28, 0.22, and 0.62 observed in shallow, deep, and non‐irrigated plants grown in the September to November period, respectively, indicate that the rate of root growth was increased in nonirrigated alfalfa as a result of limited water stress and under low evapotranspirational demand.

Alfalfa Water Use and Production on Dryland and Irrigated Sandy Loam1

AbstractField studies were conducted during a 4‐year period to determine “Vernal“ alfalfa (Medicago satva L.) dry matter yield in response to irrigation and fertilization variables. In the Northern Great Plants alfalfa forage production contributes significantly to overall agricultural land use; consequently optimization of resources use is desirable. Limited available information has created a need for such research.This study was carried out on a Maddock sandy loam soil, a member of the sandy, mixed frigid Udorthentic Haploboralls. Four irrigation levels, ranging from dryland to excessive irrigation, were established as whole plots in a randomized block, split plot design. Eight different fertilizer treatments of P, K, and S were applied to split plots during the 1st year of the study. Under a three harvest per season management system dry matter yield was significantly affected by harvest number and irrigation treatment each year. Within the dryland and deficient irrigation treatment by year, yields decreased with each cutting; with optimum and excessive irrigation, yields varied inconstantly with cutting; yields increased 14 to 330% over dryland by increasing irrigation applications. Total seasonal crop water use, or evapotranspiration (ET), was determined using a water balance approach. Drainage (DRAIN) was calculated, using flux gradients calculated from tensiometer data, and appropriate soil properties. Other inputs, including irrigation (IRR), growing season precipitation (PPT), and soil water depletion (DEPL), were measured. In addition, water use efficiency (WUE) was calculated by treatment by year. Multiple linear regression analyses were used to relate actual dry matter yield (YIELD) and relative yield (RELY) to several independent variables. When plant water stress existed throughout the growing season, RELY correlated with relative evapotranspiration (RELET) in a near perfect, linear manner. Under nonstress conditions IRR, PPT, and DEPL required consideration to attain nearly perfect correlation of RELY with RELET. The results of this study indicate that under plant water stress conditions, alfalfa dry matter yield is a linear function of plant water use.