Yield Water Use Efficiency Research Articles

Biomass and biomass water use efficiency in oilseed crop (Brassica juncea L.) under semi-arid microenvironments

Biomass production in arid and semi-arid regions requires a special attention owing to spatiotemporal scarcity of irrigation water wherein improved water use efficiency (WUE) of the crop is targeted. Under field conditions, the crop undergoes dynamic changes in near ground or within-canopy microenvironments. This changed microclimatic condition may have an impact on phenological response of the oilseed crop which in turn would affect biomass productivity, economic seed yield and water use efficiency of the crop. Henceforth, quantification of biomass production and its WUE of oilseed Brassica crop is essentially required owing to have better understanding of the crop water requirement under the era of climate change. Following a 2 years field experiment, it was revealed that the changes in leaf area index were explained by about 68–74%. The best fit polynomial third order regression analysis indicated >93% prediction in biomass production as a function of time factor. Improved biomass partitioning into economic sinks was also observed. Small scale change in near ground microenvironment may reduce the prediction of biomass variability to the extent of 3%. The mean ET variations were observed as 2.4, 1.5 and 3.2 mm day−1 during the critical phenological stages. Mean seed yield, biomass WUE and seed yield WUE ranged between 2.71 and 2.87 Mg ha−1, 11.4 and 13.1 g m−2 mm−1 and 19.3 and 22.9 kg ha−1 mm−1 respectively. Variations in both biomass and seed yield water use efficiencies due to small scale change in near ground microclimates were revealed.

Yield Traits and Water and Nitrogen Use Efficiencies of Bell Pepper Grown in Plastic-Greenhouse

We report the results of a two-year study assessing the effects of nitrogen fertilization and irrigation regimes on yield traits and on water and nitrogen use efficiency of greenhouse-grown bell pepper (Capsicum annuum L.). The trials involved the combination of four N doses (0, 100, 200, 300 kg ha-1) with two irrigation regimes (100% restitution of ETc; repeated cycles of water stress starting from fruit set). In the second year, the crop was transplanted one month earlier than in the first year and was mulched with plastic sheeting. The highest yield in both years was obtained by associating 100% restitution of ETc and the N dose of 200 kg ha-1. The marketable yields were 37 and 72 t ha-1 in 1998 and 1999, respectively. Doubling of the yield in the second year was probably due to the earlier transplantation and mulching, confirming the numerous benefits of the latter technique. The water deficit imposed during the late flowering-early fruit set phase had negative effects on the crop, with declines of the marketable yield of up to 44% due to the reduced number and weight of the fruit and the increased waste, mainly peppers with blossom-end rot, cracking, sun-burn and malformations. The peppers grown under water stress were richer in dry matter and soluble solids. The yield declines due to water deficit varied in relation to the N dose, as confirmed by the numerous interactions recorded between irrigation regime and nitrogen level.Without nitrogen fertilization, the quantity and quality of the fruits remained unchanged, while the maximum dose (300 kg ha-1) enhanced the negative effects of the water deficit on the number (-52%) and weight (-161%) of marketable peppers. Moreover, the waste peppers reached 31% of the total production (by weight), with over 21% affected by blossom-end rot. Water stress led to a drastic reduction of the total above-ground dry biomass (40%) and a significant decrease of nitrogen absorption by the plant (54%) with preferential translocation towards stems and leaves, as shown by lower Harvest Index (HI) values. Regarding the water use efficiency (WUE), the above-ground dry matter WUE (AGWUE) remained unchanged while the total yield WUE (TYWUE) and marketable yield WUE (MYWUE) decreased. The N dose of 200 kg ha-1 maximized the yield and quality of the peppers, with and without water stress, and the values of water and nitrogen use efficiency were maximal in these conditions.

Carbon Isotope Discrimination and Other Surrogates of Water Use Efficiency for Tomato Under Various Soil Moistures

ABSTRACT Carbon isotope discrimination (Δ‰) is negatively correlated with water use efficiency (WUE) in several C3 species and was proposed as a selection criterion for improving WUE. Tomato (Lycopersion esculentumL.), cv. Improved Apollo, was exposed to soil moisture levels, saturated, field capacity (FC) and deficit soil moisture conditions, in a container experiment in a screenhouse. The objective was to test for: (1) difference between soil moisture levels as they affect water use efficiency, biomass production, and distribution; (2) evaluate the relationship between various measures of WUE and carbon isotope discrimination (Δ‰), between biomass production and Δ‰, and between stem diameter (SD) and WUE and, the use of SD as an alternate surrogate; and (3) discern the physiological processes associated with changes in WUE and Δ‰ with respect to different soil moisture levels in a heavy clay soil. Tomato plants responses were quantified in terms of biomass and fresh fruit yield, plant morphology, leaf gas exchange properties, WUE of biomass, and fruit, as well as Δ‰ by leaves. While number of leaves and nodes, and leaf area were least in the saturated treatment and greatest at FC; stem diameter at harvest was greatest under saturated conditions. Stem diameter was positively correlated with Δ‰, indicating the possibility of using stem diameter as a surrogate of WUE based upon dry weight of biomass or fruit, and for negative relationships between Δ‰. Midday leaf water potential and relative water content decreased with increasing moisture stress (deficit or saturated conditions). However, leaf chlorophyll concentration decreased as soil moisture content increased from deficit to FC to saturated. Fresh fruit yield was significantly greater at FC (4.476 kg/plant) compared with saturated (2.617 kg) and deficit (1.985 kg) treatments, as aresult of greater mean weight/fruit rather than more fruit/plant. As fresh fruit yield and dry matter content of fruit were negatively related, the WUE of fresh fruit was not inversely related to Δ‰. The data indicate that in tomato, where marketable yield consists of fresh produce, the established negative relationship between WUE and Δ‰ does not hold true, and benefits of using Δ‰ as a surrogate for fresh yield WUE may not be effective while the strong negative correlation between SD and WUE suggests possibility of employing SD as surrogate of WUE.

Drought resistance, water-use efficiency, and yield potential—are they compatible, dissonant, or mutually exclusive?

This presentation is a concept review paper dealing with a central dilemma in understanding, designing, and acting upon crop plant improvement programs for drought conditions. The association among yield potential (YP), drought resistance (DR), and water-use efficiency (WUE) is often misunderstood, which in turn can lead to conceptual oversight and wrong decisions in implementing breeding programs for drought-prone environments. Although high YP is the target of most crop breeding programs, it might not be compatible with superior DR. On the other hand, high YP can contribute to yield in moderate stress environments. Plant production in water-limited environments is very often affected by constitutive plant traits that allow maintenance of a high plant water status (dehydration avoidance). Osmotic adjustment (OA) is a major cellular stress adaptive response in certain crop plants that enhances dehydration avoidance and supports yield under stress. Despite past voiced speculations, there is no proof that OA entails a cost in terms of reduced YP. WUE for yield is often equated in a simplistic manner with DR. The large accumulation of knowledge on crop WUE as derived from research on carbon isotope discrimination allows some conclusions on the relations between WUE on the one hand, and DR and YP on the other, to be made. Briefly, apparent genotypic variations in WUE are normally expressed mainly due to variations in water use (WU; the denominator). Reduced WU, which is reflected in higher WUE, is generally achieved by plant traits and environmental responses that reduce YP. Improved WUE on the basis of reduced WU is expressed in improved yield under water-limited conditions only when there is need to balance crop water use against a limited and known soil moisture reserve. However, under most dryland situations where crops depend on unpredictable seasonal rainfall, the maximisation of soil moisture use is a crucial component of drought resistance (avoidance), which is generally expressed in lower WUE. It is concluded that the effect of a single ‘drought adaptive’ gene on crop performance in water-limited environments can be assessed only when the whole system is considered in terms of YP, DR, and WUE.

Birdsfoot Trefoil Seed Production: I. Crop‐Water Requirements and Response to Irrigation

Forage legume seed crop reproduction can be modified by regulating soil-water availability. However, responses to water stress differ for each spedes, so a single optimal water management strategy is not available for all crops. The objectives of this research were to determine the crop-water requirements and the optimal water management conditions for birdsfoot trefoil (Lotus corniculatus L.) when grown for seed production under humid temperate marine climatic conditions of western Oregon, USA. The experiment was conducted on a Woodburn silt loam soil (fine-silty, mixed, mesic Aquultic Argixeroll) near Corvallis. Four single-application treatments varying in water depletion percentage (30 and 60% of field capacity) and replenishment amount (50 and 100% of amount depleted) were applied in 1994 and 1995. A low-stress treatment (LS) that received two to three applications per week of the amount depleted since the last application and a non-irrigated control were also investigated in 1994, 1995, and 1996. Increasing amounts of applied water resulted in increased seasonal crop evapotranspiration (ET C ) with plants grown under low-stress having the greatest ET C and non-irrigated control plants the least (r = 0.91). The fraction of available soil water used by non-irrigated plants was greatest and the LS treatment the least of all treatments. For non-irrigated conditions, the crop-water requirement ranged from 240 to 255 mm. Soil-water conditions favorable for high vegetative development were opposite of the conditions for optimal seed yield water-use efficiency, Unlike other forage legume seed crops, birdsfoot trefoil grown under these conditions required minimal or no supplemental irrigation to achieve maximal seed yield.