Transpiration Water Use Efficiency Research Articles

Impact of climate, rising atmospheric carbon dioxide, and other environmental factors on water-use efficiency at multiple land cover types

Rising atmospheric CO2, changing climate, and other environmental factors such as nitrogen deposition and aerosol concentration influence carbon and water fluxes significantly. Water-use efficiency (WUE) was used to analyze these factors over 3 decades (1981–2010) using the Community Land Model 5.0 (CLM5.0). The study analyzes the effects of climate and other environmental factors on multiple land cover types (forest, grassland, and cropland) with divided study periods (1981–2000 and 2001–2010). Ecosystem WUE (EWUE) and transpiration WUE (TWUE) increased at the forest site due to the CO2 fertilization effect but decreased at the grassland and cropland sites due to lower gross primary production and higher/lower (cropland/grassland) evapotranspiration as consequences of rising temperature and water availability. Inherent WUE confirmed that EWUE and TWUE trends were controlled by the rising temperature and CO2-induced warming through an increase in vapor pressure deficit. In this way, forest and cropland sites showed warming patterns, while the grassland site showed a drier climate. The later period (2001–2010) showed steeper trends in WUE compared with the earlier period at all sites, implying a change in climate. The results showed implications for rising temperature due to increased CO2 concentration at multiple land cover types.

Effects of Converting from Sprinkler to Drip Irrigation on Water Conservation and the Performance of Merlot Grown on a Loamy Sand

Effects of converting from overhead sprinkler to drip irrigation on the growth, leaf gas exchange, and fruit production of Merlot grapevines with and without cluster thinning were determined over four years. Drip or sprinkler irrigation was applied to the loamy sand soil when in-row soil moisture was depleted to <8%. Irrigation frequency averaged 50% higher (27 compared with 18 times per year) under drip than sprinkler irrigation, but 64% less water (574 compared with 1580 L per vine per yr) was applied on average under drip. Maps of moisture in the soil profile revealed differences in moisture distribution and dry-down dynamics in response to irrigation method. Increasing soil dry-down rates over years indicated that roots proliferated within the drip-irrigated soil volume. Converting to drip reduced the growth and survival of floor vegetation. Vine vigor, leaf gas exchange, and crop yield were reduced but crop yield recovered in the second year and vigor recovered by the fourth year. Stomatal conductance and leaf gas exchange remained lower under drip irrigation. Transpirational water-use efficiency was higher under drip than sprinkler irrigation in the first three years. Input water use efficiency averaged 2.5 times higher under drip irrigation over the four years. Fruit maturation was advanced by drip compared with sprinkler irrigation each year and was associated with increased cluster exposure and higher ambient temperatures. Cluster thinning also advanced fruit maturation but reduced crop yield substantially each year and had only minor interactions with irrigation method.

Biomass allocation, relative competitive ability and water use efficiency of two dominant species in semiarid Loess Plateau under water stress

A better understanding of the growth and interspecific competition of native dominant species under water stress should aid in prediction of succession in plant communities. In addition, such research would guide the selection of appropriate conservation and agricultural utilization of plants in semiarid environments that have not been very well characterized. Biomass production and allocation, relative competitive ability and water use efficiency of one C 4 herbaceous grass ( Bothriochloa ischaemum) and one C 3 leguminous subshrub ( Lespedeza davurica), both important species from the semiarid Loess Plateau of China, were investigated in a pot-cultivation experiment. The experiment was conducted using a replacement series design in which B. ischaemum and L. davurica were grown with twelve plants per pot, in seven combinations of the two species (12:0, 10:2, 8:4, 6:6, 4:8, 2:10, and 0:12). Three levels of water treatments included sufficient water supply (HW), moderate water stress (MW) and severe water stress (LW). These treatments were applied after seedling establishment and remained until the end of the experiment. Biomass production and its partitioning, and transpiration water use efficiency (TWUE) were determined at the end of the experiment. Interspecific competitive indices (competitive ratio (CR), aggressiveness (A) and relative yield total (RYT)) were calculated from the dry weight for shoots, roots and total biomass. Water stress decreased biomass production of both species in monoculture and mixture. The growth of L. davurica was restrained in their mixtures for each water treatment. L. davurica had significantly ( P < 0.05) greater root:shoot allocation than B. ischaemum for each water treatment and proportion within the replacement series. Aggressiveness (A) values for B. ischaemum with respect to L. davurica were negative only at the proportions of B. ischaemum to L. davurica being 8:4 and 10:2 in LW treatment. B. ischaemum had a significantly ( P < 0.05) higher CR value under each water treatment, and water stress considerably reduced its relative CR while increased that of L. davurica. RYT values of the two species indicated some degree of resource complimentarity under both water sufficient and deficit conditions. The results suggest that it is advantageous for growing the two species together to maximize biomass production, and the suggested ratio was 10:2 of B. ischaemum to L. davurica because of significantly higher ( P < 0.05) RYT and TWUE under low water availability condition.

Seedling Biomass Partition and Water Use Efficiency of Switchgrass and Milkvetch in Monocultures and Mixtures in Response to Various Water Availabilities

Seedling biomass and allocation, transpiration water use efficiency (TWUE), and species competition between switchgrass (Panicum virgatum L.) and milkvetch (Astragalus adsurgens Pall.) were investigated in a pot-cultivated experiment under different levels of water availability. The experiment was conducted using a simple replacement design in which switchgrass and milkvetch were grown in growth chamber with ten seedlings per pot, in three combinations of the two species (0:10, 5:5 and 10:0). Five water treatments included sufficient water supply (HW), gradual soil drying from HW (DHW), moderate water stress (LW), gradual soil drying from LW (DLW), and re-establishment of LW conditions after 12 days of drying from LW (RLW). Water treatments were applied over a 15-day period. Biomass production and its partitioning, and TWUE were determined at the end of the experiment. Species competitive indices (competitive ratio (CR), aggressivity (A) and relative yield total (RYT)) were calculated from the biomass dry weight data for shoots, roots and total biomass. Water stress significantly reduced seedling biomass production but increased root:shoot ratios in both monocultures and mixtures. In the RLW treatment, only switchgrass monocultures displayed compensatory biomass production and TWUE, while both species demonstrated compensatory growth in the mixture. Switchgrass was the dominant species and much more aggressive than milkvetch in the LW treatment, while in the other four treatments milkvetch was the dominant species as measured by the positive value of aggressivity and higher values of CR. The total biomass RYT values of the two species were higher than 1.0, indicating some degree of resource complimentarity. In the two-species mixture, although the biomass production was lower than that of milkvetch in the monoculture, there was better TWUE, especially under low and fluctuating water availability.

Mineral nutrition and water use patterns of a maize/cowpea intercrop on a highly acidic soil of the tropic semiarid

Due to global warming, water is expected to become scarce especially in semiarid regions. Therefore, there is a need to increase the efficiency in water use by crops under rainfed agriculture. The effect of nutrient availability on the growth, production, root development, water relations and water use efficiency (WUE) by the intercrop maize/cowpea was investigated in 2 contrasting years (dry and wet) in the semiarid region of Brazil. The crops were grown on a strongly acidic, sandy soil with three treatments: (i) application of NPK fertilizers plus lime (NPK + lime), (ii) application of NPK fertilizers (NPK) and (ii) control (Contr.) in low and high input regimes. The soil water balance was calculated with the crop model EPICSEAR. Application of fertilizers and lime increased biomass production and grain yield of the intercrop up to 400% and 550%, respectively, and maize suffered more from the effects of low nutrient availability and soil acidity than cowpea. The root development of both crops was strongly improved by the application of NPK and lime and cowpea developed a deeper root system which enabled this crop to keep a higher transpiration rate in the dry year. As a consequence of the shallow root system, maize was prone to water stresses caused by the dry spells and its harvest index was reduced when dry spells occurred during flowering and grain filling. Fertilizers and lime application reduced deep percolation and soil evaporation while increasing the productive transpiration flow. WUE were improved through the application of nutrients and lime and maize showed higher WUE than cowpea. The omission of lime showed only minor effects on the evaporation and transpiration WUE. The model probably over-emphasizes the effects of high Al saturation on the root growth and water uptake and consequently underestimated the transpiration rate of the crops. Nevertheless, the gross WUE was reduced up to 58% when lime was omitted and NPK applied at high inputs. A balanced fertilization in combination with lime improves the root development of a maize/cowpea intercrop in acid Acrisols of the semiarid NE of Brazil. The improved root development allows a better use of soil water reserves and increases the WUE of the system.

WATER USE EFFICIENCY OF GREENHOUSE SUMMER SQUASH IN RELATION TO THE METHOD OF CULTURE: SOIL VS. SOILLESS

WATER USE EFFICIENCY OF GREENHOUSE SUMMER SQUASH IN RELATION TO THE METHOD OF CULTURE: SOIL VS. SOILLESS

Effects of irrigation, nitrogen and gypsum on yield, nitrogen accumulation and water use by wheat

Responses of wheat grown on a heavy clay soil in the Goulburn-Murray Irrigation Region of south-eastern Australia to a factorial combination of three irrigation treatments and nitrogen and gypsum application were investigated.Irrigation treatments included a rainfed control (treatment R F) and irrigation on either a weekly (treatment I w) or fortnightly (treatmnt I F) basis beginning in spring and maintained until physiological maturity. Nitrogen was applied at 0 and 150 kg N ha −1 (treatments N 0 and N 150, respectively) and gypsum at 0 and 5 t ha −1. Nitrogen and gypsum treatments were applied at sowing. Yield increased from a mean of 4 t ha −1 treatment R F to 6.6 t ha −1 in treatments I F and I W, largely because of promotive effects of irrigation on kernel weight (increase from 31 mg to 42 mg kernel −1 and kernel spikelet −1 (1.4 as compared with 1.7). Seasonal conditions and the relative fertility of the site were sufficient to maximise spike number and spikelet spike −1. Nitrogen increased kernel spikelet −1 but effects on yield were not significant because of a decrease in kernel weight. Effects of gypsum on yield were not significant. Water-use efficiency of both rainfed and irrigated treatments was ca. 1.25 g grain kg −1 H 2O. However, transpirational water-use efficiency, calculated after allowing 110 mm water for soil evaporation, fell from 2 g kg −1 in treatment R F to 1.7 and 1.5 g kg −1 in treatments I F and I W, respectively. The decrease was ascribed, in part, to lodging and soil evaporative losses may have been in excess of 110 mm with more frequent irrigation. Effects of N on water use could not be distinguished, again because of the initial fertility of the site, which supported rapid growth and resulted in complete canopy closure. Nitrogen and irrigation treatments had independent effects on the concentration of N in the grain (% N G ) which increased by a mean of 0.6% with N treatment despite a decrease in N harvest index (HI N) from 0.77 to .70. Irrigation decreased % N G by approximately 0.5%. Approximately 90 kg pN ha −1 was found in the grain of treatments R FN 0, I WN 0, I wN 0 and R FN 150 and differences in % N G in these treatments attributed to a ‘dilution’ effect mediated by the increase in yield effected by irrigation. The grain accounted for approximately 115 kg N ha −1 in treatments I FN 150 and I WN 150, countering the inverse relationship between % N g and yield despite the increase in HI N index caused by N application.