ASHS 2024 Conference

In the Central Serrana region, Espírito Santo state, Brazil, there is a predominance of small farms and the technological level used is still low, especially in terms of water use. Irrigation management can provide greater water use efficiency and promote optimization of crop productivity and conservation of water resources. Thus, this study aimed to implement an irrigation management program, using simplified electronic spreadsheets, for drip irrigation, based on the climatological water balance, for family-based farmers. We selected four spots located in the towns of Barra de Bom Destino; Barra de Jatibocas; Baixo Sossego and headquarters of the Itarana County, state of Espírito Santo, Brazil, with drip irrigation systems, irrigating banana, arabica coffee, guava and conilon coffee crops. Irrigation management was carried out for seven months, using daily temperature and precipitation data, obtained from maximum and minimum thermometers and rain gauges, respectively. The values were collected by farmers, noted in tables and registered in electronic spreadsheets, which provided recommendations for irrigation times. In adjacent areas, irrigation was carried out according to its local traditional rule, in the way that farmers did before the implementation of management, with the purpose of comparing the volume of water used in the two forms of irrigation. The banana irrigator followed the irrigation management guidelines using the spreadsheet and, comparing the two areas, achieved a 7.5% increase in productivity and a 9.34% increase in water use efficiency. Farmers in areas with arabica coffee and guava managed irrigation, but were not organized to collect crop productivity data. For guava cultivation, an increase in fruit load was visible in the area with irrigation management. The Conilon coffee farmer did not follow the irrigation management recommendations, considering the task laborious and complicated. Irrigation management continues to be carried out on farms with banana, guava and arabica coffee. New neighboring producers expressed interest in using electronic spreadsheets. Work has been done on the development of new tools for irrigation management, using smartphones, to facilitate the task of calculating irrigation management. Therefore, it is expected that with the continuity of the work, the practice of irrigation management will be more widespread among farmers and they will decide to use it.

Clogging poses significant economic risks in greenhouse micro-irrigation systems. While water quality classification systems aim to assess the overall risk of clogging in micro-irrigation systems, they haven’t been evaluated for their ability to predict potential clogging based on water quality characteristics, particularly in controlled environment agriculture. Understanding these causes can inform robust thresholds and effective water management strategies to mitigate economic risks associated with clogging. This project aimed to evaluate if the existing classification systems could be used to identify the cause of clogging in micro-irrigation systems in greenhouses. Water from eight commercial greenhouses with reported clogging was analyzed for physical, chemical, and biological properties to rate the risk of clogging according to the classification systems. In general, iron and manganese from the fertilizers and high microbial load resulted in high ratings. However, the ratings lacked insight into the specific causes of clogging, disregarding interactions among chemical and microbial factors and qualitative characteristics of specific microbial phenotypes (e.g., production of polysaccharides or iron oxidation) that lead to clogging. Furthermore, the systems overemphasize nutrient levels typically used in greenhouse fertigation as the cause of clogging—which is not commonly observed in practice. Enhancing these systems requires parameters that reflect interactions among water quality parameters and the influence of microbial traits on clogging. Further research needs to develop these parameters in new systems with robust and precise thresholds in which emitter performance, profitability, and sustainability are affected.

An open-source data-driven irrigation controller, "Open_Irr", was developed by USDA-ARS as a low-cost (≤ $250 USD) entry point to autonomous irrigation installations in horticultural production and research applications. The device is reliant on granular-matrix type Watermark soil tension sensors (n≤16) from which it acts as a datalogger; sensors can be partitioned into 4 groups for water management in which readings can be used to output a logic-level signal for opening valving to initiate irrigation events. Here, we demonstrate the use of the device in research applications for imposing drought stress in containerized plantings of apple (Malus domestica). Our primary objectives were to (i) determine the utility of using granular matrix type soil tension sensors for predicting plant physiologic responses, measured by growth habit, infrared gas exchange, and chlorophyll fluorescence, for improvement of decision support systems; and (ii) determine potential differences in cultivar performance under water deficit conditions. A trial examined performance of ‘B.9’ rootstock grafted to ‘Autumn Gala’, ‘CrimsonCrisp’, and ‘Golden Delicious’ scions at set soil matric potential thresholds for irrigation events (-25, -40, -60, and -80 kPa). A second trial examined five rootstock cultivars (‘B.10’, ‘B.9’, ‘G.11’, ‘G.935’, and ‘G.969’) grafted to a common ‘Honeycrisp’ scion as plant available water contents of the soil were theoretically progressively decreased by 5% each week. Correlation matrices between aspects of physiology and soil matric potential revealed Pearson’s r ≤ |0.43| yet further regression analysis offered potentially useful data shapes warranting further exploration. A piecewise regression suggested soil matric potential could predict, to an extent (r2 = 0.29), the rate of change in leaf water potential upon exposure to water deficit. The break-point of the piecewise regression in leaf and edaphic potentials was respectively -30.6 kPa and -0.73MPa, which may prove useful for incorporation in developing irrigation decision support systems. The pattern of stomatal response to deficit suggested enhanced stomatal regulation capacity of ‘Gala’ relative to other scions in which nonstomatal factors likely contributed to short term maintenance of photosynthetic C assimilation rates. Similarly, the ‘G.935’ rootstock demonstrated superior sensitivity to water deficit through rapid stomatal closure relative to other cultivars. Refinement of the relationships between arduous measures of physiologic function with correlated easy-to-automate proxy measures is advised for potential advancement of irrigation decision support systems.

Biofilms clog irrigation systems, thus affecting water use efficiency, crop yields, and production costs. Microbial attachment and subsequent biofilm accumulation is influenced by the irrigation water quality and materials used in the design of water distribution systems. Therefore, the goal of this research was to evaluate if the pipe material and the load of organic matter in nutrient solutions affected biofilm accumulation, microbial community composition, and emitter performance. Nutrient solutions had 0, 30, 60, and 120 mg·L-1 peat particles under 150 µm in diameter and flowed through pipe loops made of polyvinyl chloride (PVC) and polyethylene (PE). The emitters were pressure compensated drippers with anti-drain mechanism and a nominal discharge of 2 L·h-1. Heterotrophic plate counts and biofilm dry mass were used as indicators of biofilm accumulation. DNA was extracted from the biofilm then sequenced for bacterial community composition analysis. The surface of new and post-biofilm pipes was characterized by measuring hydrophobicity and roughness to evaluate the effects of biofilm on the pipe’s surface. None of the emitters clogged, but there was an increase in discharge with 60 and 120 mg·L-1 peat. This observation suggests that the particles and biofilm accumulation affected the operation of the emitters’ anti-drain mechanism. The pipe material had more influence on the accumulation and bacterial community composition of biofilms than the organic load of the nutrient solution. Overall, biofilm accumulated more on PVC pipes than on PE pipes. The hydrophobicity of PVC pipes decreased, and roughness of PVC and PE pipes increased after biofilm colonization. These results suggest that the characteristics of the pipes can influence and be influenced by biofilms and therefore affect the risk of clogging. Our results also suggest that biofilms establish better on materials that biodegrade easy and that biofilm changes the roughness of PVC pipes which may further affect pipe longevity.

Traditional methods of microbial quantification for irrigation water using colony counts from agar culture require dedicated laboratory space and trained personnel, making them less suitable for on-site application by horticulture growers. Dehydrated Petrifilm™ culture plates are a simpler method than agar, but are still time-consuming and require 2-3 days to culture. Adenosine Triphosphate (ATP) tests may provide an easy and reliable method for quantifying microbes in water that is more rapid than culturing microbes. The objective was to compare ATP measurements against colony counts cultured using Petrifilm™ for assessing microbial water quality. Lake water was recirculated through an ozone system until a target oxidation reduction potential (ORP) of 700 mV was reached. Samples were collected at the following ORP intervals: control, 300 mV, 400 mV, 500 mV, 600 mV, and 700 mV. Samples were plated for aerobic bacterial counts and yeast and mold counts using Petrifilm™ culture plates. Samples were also analyzed for free and total ATP concentration using the Hygiena EnSURE luminometer and its accompanying free and total ATP swabs. Microbial ATP was calculated by subtracting free ATP from total ATP. Results showed a consistent decrease in bacterial and fungal counts with increasing ORP using Petrifilm™ culture plates. At 700 mV ORP, there was 99.5% reduction of bacterial colony counts and 92.8% reduction of fungal colony counts from the initial. Similarly, a decreasing trend was observed for free, total, and microbial ATP concentration with increased ORP levels. There was a 97.5 % reduction of microbial ATP from the initial concentration at 700 mV ORP. A positive correlation was observed between microbial ATP measured with the luminometer and bacterial counts obtained from Petrifilm™. Integrating ATP quantification into routine monitoring practices could provide easy and rapid results and enhance the efficacy of microbial assessments in irrigation water.

Nurseries and greenhouses in California face challenges of limited water supply and increased scrutiny from water quality regulators. Improving irrigation efficiency thus minimizing irrigation runoff are the main strategies to save water and comply with regulations. Evapotranspiration-based (ET) methods that make use of weather station data has the potential to substantially improve efficiency. In California, a statewide network maintained by DWR CIMIS project is widely used. However, crop-specific coefficients to calculate irrigation needs from weather data are not widely available in the nursery industry, particularly for large (15-gal and up) containers. In this project we measured water use and developed crop coefficient for 15-gal trees, one low water user (Olive, Olea europaea) and two high water users (Sycamore, Platanus acerifolia and Ficus microcarpa) with different canopy architectures. Container weight was measured with load cells (Omega LC103B, a weighing device similar to a scale), with values logged every minute by a Campbell Scientific data logger (CR1000X). Daily water use was calculated as the difference in weight from after each irrigation to before the following one. Local CIMIS reference ET was used to calculate crop coefficients. Tree water use yielded crop coefficients averaged 1.19 for Ficus; 0.57 for Olive and 1.21 in Sycamore during fall 2023 before defoliation started to occur for Sycamore in mid-October. Olive and Ficus defoliated through winter reaching the lowest crop coefficient in March 2024 when the coefficient was 0.42 for Ficus; 0.22 in Olive and 0.12 in Sycamore. Crop coefficients were substantially lower than those presented by Burger et al., 1987. for similar woody ornamentals grown in 1-gal containers. The difference is that Burger’s crop coefficients were calculated using the container surface area, while we used the (larger) block area divided by the number of containers. While less meaningful from a plant physiology point of view, a block-based crop coefficient is more useful for irrigation management and more similar to the crop coefficient calculation in field crops, grape vines and fruit trees. Results from our method can be converted to Burger et al. method by dividing by interception efficiency (i.e. cumulative container surface area divided by irrigation block area).

Container nurseries produce a high volume of operational water (OW) during irrigation and storm events. OW is irrigation return flow (IRF) and storm runoff that has traveled through crop production areas and could carry sediment and agrichemicals, making nurseries a potential contributor to nonpoint source pollution. OW is collected in retention reservoirs for treatment and reuse or allowed to leave the site. A monitoring program was conducted on five production areas (study catchments) with two different irrigation systems (i.e., overhead and spray stake) in two container nurseries located in the Midwestern USA (Central Lowland physiographic region). Total suspended solid (TSS), dissolved inorganic nitrogen (DIN) and phosphate (PO4-P) in OW during storm and irrigation events. We found median event mean concentrations (EMCs) during irrigation events for TSS, DIN, and PO4-P were 131 mg∙L-1, 2.9 mg∙ L-1, and 1.2 mg∙ L-1, respectively. During storm events, DIN and PO4-P EMCs were similar to irrigation events; however, TSS EMCs were almost 8 times greater than those of irrigation events. The median daily TSS, DIN and PO4-P load per ha during storm events were 13.3 kg·ha−1·day−1, 82.3 g·ha−1·day−1 and 43.5 g·ha−1·day−1, respectively, which were 20, 3, and 4 times greater than those of irrigation events. The results indicated that the portion contribution of storm and irrigation for producing TSS was 86% and 14%, respectively. The results of this study can facilitate improved irrigation scheduling and help assess potential treatment options.

Traditional irrigated landscapes and in particular turfgrass dominated landscapes are being challenged across the U.S. due in part to the demand on potable water supplies. So called “ornamental” turfgrass will be outlawed in Nevada by 2027 and efforts are underway in other areas of the desert southwestern states to do the same. Meanwhile, in these areas, aggressive turfgrass removal programs utilizing financial incentives are occurring. This dramatic change is due to water supply associated with the Colorado River and western water supply in general. In the eastern U.S. changes are occurring in new development in North Carolina warm season grasses are displacing cool season grasses in new landscapes. Accordingly the new trend is to install bermudagrass without irrigation. In Florida, numerous municipalities have or are adopting codes mandating a maximum of the landscaped area as 60% sprinkler irrigation, which means turfgrass, and in some municipalities as low as 20% of the landscaped area. The remainder of the landscaped area is filled with a mixture of microirrigated ornamentals, mulched area, or unirrigated turfgrass. Some newer developments are eliminating irrigated turfgrass altogether. The Florida-Friendly Landscaping (FFL) program is uniquely positioned to deliver education relevant to the radical change that is occurring in designed and built landscapes. Many local governments are adopting landscape codes that include or mandate FFL principles. This talk will discuss these trends along with the factors driving this cultural change of landscapes and in particular the use of turfgrass in landscapes. Additionally, the talk will focus on the challenges ahead for landscapes under water supply constraints and how they may impact nonpoint source pollution from urban areas.