Irrigation Reduction Research Articles

Reduced Irrigation during Orchard Establishment Conserves Water and Maintains Yield for Three Cider Apple Cultivars

Irrigation water productivity is a priority for sustainable orchard management as water resources become more limiting. This study evaluated reduced irrigation (RI) as a management strategy for cider apple (Malus domestica Borkh.) production in 2019 and 2020 in northwestern Washington, which has a Mediterranean climate and averages 14.1 cm of precipitation from June to September. RI was evaluated on three cider apple cultivars, Dabinett, Porter’s Perfection, and Golden Russet, in their third and fourth leaf. Stem water potential (stem ψ) was measured weekly throughout the growing season to monitor water stress and implement the RI treatment: irrigation would be applied when stem ψ values dropped below −1.5 MPa, a threshold indicative of moderate water stress in apples. Soil water potential was monitored throughout the season, vegetative growth was assessed by measuring shoot length and non-destructive imaging of the plant canopy using lateral photography, and yield, fruit quality, and juice quality were measured at harvest. Moderate water stress as indicated by stem ψ did not occur either year, thus irrigation was never applied to the RI treatment plots. There was a negative relationship between average stem ψ and both yield and air temperature (P < 0.0001 for each); as yield increased by 5.9 kg per tree or temperature increased by 3.3 °C, stem ψ decreased by 0.1 MPa. The juice quality attributes of the three cultivars in this study were similar to their historic measures at this site and there were no differences due to irrigation treatment, likely because trees did not reach the threshold to induce physiological stress. Both years, trees in the RI treatment did not differ from the control treatment in vegetative growth, fruit yield, juice yield, or any juice quality attribute, but weight per fruit decreased by 7 g, and fruit firmness (measured only in 2020) increased by 2 N. Results from this study indicate that fruit yield and quality in an establishing orchard can be maintained when irrigation is reduced relative to crop water requirements that are estimated from a calculated water balance or relative to conventional grower practices for this region. This finding highlights the benefits of using plant water status to schedule irrigation.

Physiological Responses of Coffee (Coffea Arabica L. VAR. Castillo) Plants to Biochar Application Under Water Deficit Conditions

Drought is one of the main abiotic stresses in coffee crop, and the use of biochar (BC) has been considered an alternative to mitigate this kind of stress. Plants of the Castillo variety were grown in pots and PVC pipes filled with silt loam soil in two separate experiments to evaluate the effect of the coffee pulp biochar application on the physiological responses under water deficit conditions. Four different BC doses (0, 4, 8, and 16 t ha-1) were incorporated. Water deficit was imposed through the progressive reduction irrigation (25%, 50%, 75%, and 90% of water lost via evapotranspiration). Gas exchange, maximum quantum yield of PSII (Fv/Fm), biomass, and water status were measured. Reduced irrigation (RI) negatively affected Fv/Fm , leaf gas exchange, biomass, and water status. 8 t ha -1 (BC) increased photosynthesis in both well-irrigated (WI) plants (6 µmol m-2 s-1) or with RI (3.5 µmol m-2 s-1) compared to 0 t ha -1 BC (RI: 1.8 µmol m-2 s-1 and WI: 3.9 µmol m-2 s-1). To summarize, 8 t ha-1 BC can be a recommended practice for coffee production not only to capture carbon and reintroduce it to the soil, but also to alleviate the effects of moderate water deficit.

Effect of Reduced Irrigation on Growth and Flowering of Coneflower and Sneezeweed

Reduced irrigation (RI) can be used to reduce irrigation volume as well as to control plant growth. The timing and duration of RI applications can affect overall plant growth and flowering. Knowledge of plant response to RI can allow growers to control growth and plant form. The objective of this study was to quantify flower and overall plant growth of ‘PAS702917’coneflower (Echinacea purpurea) and ‘Helbro’ sneezeweed (Helenium hybrida) in response to RI. A soil-moisture sensor automated irrigation system was used to apply four irrigation treatments: RI and well-watered (WW) controls (25% or 38%) and two alternating treatments to apply RI for either the first 2 weeks (25% followed by 38%, RIWW treatment) or final 4 weeks (38% followed by 25%, WWRI treatment) of the 6-week study. For the sneezeweed experiment, RI was reduced to 20%. For coneflower, peduncle length was greater for the WW (36.8 cm) and RIWW treatments (35.7 cm) than the RI (27.0 cm) and WWRI treatments (26.6 cm). Shoot dry weight, compactness, leaf area, and flower number were not significant. For sneezeweed, WW plants were taller (57.2 cm) and had greater shoot dry weight (49.8 g) than plants in other treatments. WW plants also had more flowers (99) than WWRI (63) and RI (67) plants, which were more compact. Total leaf area did not differ between treatments for either species. Total irrigation volume was greatest for WW plants (5.2 and 15.1 L/plant for coneflower and sneezeweed, respectively), with RI at any point during the experiment resulting in water savings.

Evaluating best management practices to lower selenium and nitrate in groundwater and streams in an irrigated river valley using a calibrated fate and reactive transport model

A calibrated fate and reactive transport model is applied to evaluate alternative water and land best management practices (BMPs) in Colorado’s intensively irrigated Arkansas River Valley to attenuate nonpoint source pollution and more closely meet regulatory standards for selenium (Se) and nitrogen (N) in groundwater and streams. Reduced irrigation (RI), lease fallowing (LF), canal sealing to reduce seepage (CS), reduced fertilizer application (RF), and enhanced riparian buffers (ERB) are explored as stand-alone BMPs, and in combination, at basic to more aggressive levels of implementation. The distributed-parameter model, which couples MODFLOW-SFR with RT3D-OTIS, predicts impacts that vary significantly over a region encompassing about 500 km2 and across time. Results suggest that, over the course of several decades, average Se and nitrate-nitrogen (NO3-N) groundwater concentrations within the region could be lowered by as much as 23% and 40%, respectively, using combined BMPs. Average Se concentration in the river could be decreased by up to 56% with combined BMPs, and NO3-N concentrations by up to 32% by using ERB. The CS-RF-ERB combination type may be the most promising for simultaneously lowering both Se and NO3-N concentrations. To insure compliance with Colorado water rights and the Arkansas River Compact with Kansas, measures must be taken to compensate for altered return flow patterns that will be a consequence of BMP implementation. Results also point to the need to consider the targeting of BMPs to specific locations within the region to maximize their effectiveness and efficiency.

Ecological and functional adaptations to water management in a semiarid agroecosystem: a soil metaproteomics approach

Climate change models point to a decrease in water availability in semiarid areas that would compromise the maintenance of sustainable agriculture. Here, we used a grapefruit agroecosystem model to evaluate the responses of the active soil microbial community – as a microbial subset directly involved in soil functionality- undergoing strategies to cope with the low water availability in south-east Spain. For this purpose, we tested the impacts of: (i) water quality: transfer-water from a river (TW) or reclaimed-water from a wastewater-treatment plant (RW); and (ii) water quantity: continuous optimal amount of water or reduced irrigation (RDI) in the temporal frame when the crop is less sensitive; and their interactions. Metaproteomics revealed that the phylogenetic diversity of the active community and its functional diversity were lowered in soils with RW. RDI lowered soil respiration and functional diversity while the phylogenetic diversity remained constant. The reestablishment of full irrigation after RDI led to a recovery of soil respiration that was accompanied by an enhanced abundance of resilient bacterial populations. Bacterial populations displayed molecular mechanisms against water stress that have been conserved evolutionarily in plants. Protein-based studies shed light on ecological and functional mechanisms that govern the adaptive responses of soil microbial communities to climate-change friendly water management.

Evaluation of Different Drought Stress Regimens on Growth, Leaf Gas Exchange Properties, and Carboxylation Activity in Purple Passionflower Plants

A greenhouse experiment was conducted to evaluate the effects of water stress on leaf water potential, plant growth, and photosynthesis in purple passionflower (Passiflora incarnata). Twenty 4-L pots with two plants in each pot were arranged in a completely randomized design. Ten pots received a daily irrigation dose of 100% evapotranspiration (ET) throughout the 43-day experiment (control). The other 10 pots were subjected to a reduced irrigation (RI) treatment, which was implemented stepwise to achieve a gradual increase in stress, by irrigating them with 50% ET first, then with 25% ET and, finally, with 10% ET. The last stress phase was followed by a recovery phase in which all treatments received the same amount of water (100% ET). A lower water potential was obtained at 10% ET compared with control plants (−2.51 and −0.98 MPa, respectively). Plants in both 25% and 10% ET irrigation treatments had reduced net CO2 assimilation rates (4.25 and 3.50 μmol·m−2·s−1, respectively) than plants watered with 100% ET (8.53 and 6.77 μmol·m−2·s−1, respectively). Values of maximum carboxylation rate allowed by rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase), calculated 31 days after treatment (DAT) application (when RI plants were irrigated with 10% ET) decreased by ≈60%, whereas rate of photosynthetic electron transport and triose phosphate use (TPU) were reduced by ≈30% and ≈45% in the stress treatment compared with the control during the 10% ET irrigation period, respectively. Values of water potential and net CO2 assimilation rates in previously stressed plants were not different from the control treatment in the recovery phase, suggesting that P. incarnata plants could adapt well to landscaping situations where periods of extreme drought can be expected.

Interactive Effects of Deficit Irrigation and Berry Exposure Aspect on Merlot and Cabernet Sauvignon in an Arid Climate

The objective of this study was to determine the main and interactive effects of a sustained water deficit during berry development and berry exposure aspect on yield and berry composition in the red winegrape cultivars Merlot and Cabernet Sauvignon. Standard (STD) and reduced (RED) levels of sustained deficit irrigation were imposed throughout berry development over four growing seasons in a field trial located in the Snake River Valley American Viticultural Area (AVA) of southwestern Idaho, United States. The STD irrigation provided ~70% of crop evapotranspiration (ETc) and the RED treatment provided ~50% of the STD. Midday leaf water potential (Ψl) was measured weekly and the diameter of exposed east- and west-facing berries was nondestructively measured during berry development. Yield and berry maturity and the phenolic composition of exposed east- and west-facing berries were measured at harvest for each irrigation treatment. Vines under RED had lower Ψl than vines under STD irrigation. Deficit severity and west-facing berry exposure had an additive effect on reducing berry growth. East-facing berries under STD irrigation grew faster than west-facing berries under RED irrigation. Yield per vine and berry growth were reduced in both cultivars under RED irrigation and west-facing berries contained less total monomeric anthocyanin per berry than east-facing berries. Reduction in total anthocyanin content was due to lower concentration per gram berry fresh weight in Merlot and reduced berry fresh weight in Cabernet Sauvignon. The lack of significant irrigation effect and significant exposure effect observed in this study supports the hypothesis that temperature is a major factor influencing berry compositional development.

Guidelines for irrigation scheduling of peach palm for heart-of-palm production in the São Francisco Valley, Brazil

The water consumption, crop coefficient and effective rooting depth of the peach palm cultivated in a Vertisol were evaluated over two years and three months, from planting to fifth harvest, in Juazeiro, Bahia State, Brazil. Plants were irrigated by microsprinklers under two irrigation treatments, full irrigation (FI) and reduced irrigation (RI), and the amount of water applied in RI corresponded to 75% of that of FI. Water consumption and crop coefficient has increased markedly at the first harvest (7.3 mm day-1 and 1.2, respectively, in FI treatment) in the thirteenth month, as a consequence of plant canopy development. After that, plants were harvested every three or four months, and these values varied a little due to decrease of the stand. The effective rooting depth was shallow (40 cm) at 12 months (before the first harvest) and it remained the same up to 24 months after planting (after the fourth harvest). Significant response of heart-of-palm yield to the irrigation treatments was not observed.