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North Logan, UT, United States

Kjelgren R.,820 Old Main Hill | Beeson R.C.,University of Florida | Pittenger D.P.,University of California Cooperative Extension | Montague D.T.,Texas Tech University
American Society of Agricultural and Biological Engineers Annual International Meeting 2015 | Year: 2015

Irrigated urban landscapes must increasingly maintain economic and ecosystem value with less water in response to droughts amplified and shifted by climate change. Efficient landscape water management requires accurately estimating water amount demanded by plants to meet minimum performance expectations. Simplified Landscape Irrigation Demand Estimation (SLIDE) Rules distills scientifically credible assumptions about urban landscape biophysical complexity into heuristic guidelines for estimating water demand that are conceptually accessible and operationally useful. SLIDE Rules are: 1) oasis urban reference evapotranspiration (ETo) reasonably represents water use of urban turf seasonally and for day-to-day for irrigation scheduling, but less reasonably represents water use of non-turf surfaces; 2) specific Plant Factors (PF) based on different responses to temperature and drought adjust ETo downward to estimate actual water demand of general plant type categories-turf, non-turf and desert-found in urban and suburban landscapes; 3) hydrozones controlled by an irri-gation valve are the smallest landscape unit manageable for water; and overall zone irrigation is gov-erned by the highest water demand plant within that hydrozone; 4) for hydrozones <80% plant cover, water use can be estimated as volume of water based of individual plants using planar leaf area expressed as projected canopy area. SLIDE Rules is a framework for creating water efficient urban landscapes based on selection of appropriate species PF's in combination with lower density spatial arrangement of plants and hardscape. SLIDE Rules is aimed at stakeholders in urban landscapes who design, regulate or manage urban landscapes to use less water.

Buckland K.,820 Old Main Hill | Reeve J.R.,820 Old Main Hill | Alston D.,305 Old Main Hill | Nischwitz C.,305 Old Main Hill | Drost D.,820 Old Main Hill
Agriculture, Ecosystems and Environment | Year: 2013

Onion thrips and Iris yellow spot virus (IYSV) are two primary yield reducing factors in onion production worldwide. Current management practices rely on heavy use of insecticides and fertilizers, threatening the sustainability of onion systems. Little is known about how cultural practices such as reduced fertility, soil biostimulants, and crop rotation affect onion yield, thrips densities, soil properties, and IYSV incidence. In a replicated field experiment, reduced nitrogen (N) (134kgNha-1, one-third the standard grower rate), slightly decreased yield and onion size. Adult thrips populations were 23 to 31% lower in the reduced as compared to standard N (402kgNha-1) and biostimulant treatment, respectively. Growing onions following a one year cycle in corn rather than wheat reduced onion thrips in one of two years. The addition of a biostimulant had no effect on soil properties, but may have slightly increased yield, attracted adult thrips, and increased thrips populations. IYSV incidence was not influenced by fertilizer rate or crop rotation. Soil microbial biomass and readily mineralizable carbon were greater following wheat, while soil nitrate (NO3 -) accumulation was greater in standard N treatments. Soil microbial activity, as measured by dehydrogenase enzyme potential, may have been adversely affected by high N rates. Results suggest that reduced N, without biostimulant, sustained onion yields, decreased onion thrips densities and potential for IYSV incidence, created a more favorable soil environment for microbial activity, and reduced the risk of NO3 - leaching. © 2013.

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