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The improvement of fertilizer efficiency is driven by narrow profit margins, environmental concerns, and resource conservation. Fertile soil is the foundation for food production and successful civilizations; it is developed and maintained through the addition of nutrients lost through harvest. However, nutrient uptake by plants is inherently inefficient and the nutrients remaining in the soil after uptake can cause negative air and water resource impacts. In addition, poor fertilizer efficiency is a waste of natural resources and potentially reduces yields, crop quality, and grower profits. Enhancing fertilizer efficiency in potato is particularly important because relatively high rates of fertilizer and water are necessary to compensate for an inefficient rooting system and extreme sensitivity to deficiencies. Several new fertilizer materials have been designed to enhance fertilizer efficiency. The modes of action of these materials include: (i) slow or controlled release to meet plant need in a more timely fashion; (ii) addition of high charge‐density materials that isolate nutrients from interfering elements and compounds; (iii) complexation or chelation of the nutrient to enhance solubility; and (iv) modification of the micro‐site pH to enhance nutrient solubility.

Soil water repellency is commonly found in piñón {Piniis spp.)-juniper (Juniperus spp.) (P-J) woodlands and may limit site recovery after a fire. Understanding the extent of this problem and the impact it has on vegetation recovery will help guide land managers in conducting their restoration efforts. In this study, we (i) examined the spatial distribution and severity of post-fire soil water repellency in a burned P-J woodland, (ii) related ecohydrologic properties to prc-fire tree canopy cover and post-fire vegetation establishment, and (iii) demonstrated a geographic information system (GlS)-based approach to extrapolate observed patterns to the lite boundary scale. During a 2-)i period, several soil and vegetative measurements were performed along radial line transects extending from the trunk of burned Utah juniper [Jumperus osteosperma (Torr.)Little] trees to twice the canopy radius. Results indicate that water tepellency patterns are highly correlated with pre-fire tree canopy cover. Critical water repellency extended from the base of the tree to just beyond rhe canopy edge, while subcritical water repellency extended half a canopy radius past the edge of the critical water repellency zone. At sites where critical water repellency was present, infiltration rates, soil moisture, and vegetation cover and density were significantly less than non-water-repellent sites. These variables were also reduced in soils with subcritical water repellency (albeit to a lesser extent). Results were exported into a GIS-based model and used in conjunction with remotely sensed imagery to estimate the spatial distribution of soil watet repellency at the landscape scale.Abbreviations: CR, canopy radius; GIS, geographic information system; P-J, piñon-juniptr; RFE, radial feature extraction; SWC, soil water content; WDPT, water drop penetration time. S ince European settlement of the western United States, piñón {Pinus spp.)and juniper (Juniperus spp.) species have expanded their range to more than 40 million ha (Romme et al., 2009), encroaching on historical grassland and sagebrush {Artemisia tridentata Nutt.) communities (Miller et al., 2008). Proposed primary-causal factors iticlude high-intensity grazing, fire suppression, increased atmospheric CO2 concentrations, and climate change (Johnson et al., 1993;West, 1999; Miller and Tausch, 2001;Romme et al., 2009). This ecosystem shift has impacted soil resources, plant community structure and composition, forage quality and quantity, water and nutrient cycles, wildlife habitat, and biodiversity (Miller et al., 2008). As P-J woodlands mature, increased fuel loads and canopy cover can lead to large-scale, high-intensity crown fires (Miller et al., 2000(Miller et al., , 2008 Miller and Tausch, 2001 ). After a fire, the ability of a site to recover depends on the extent that physical and biological processes controlling ecosystem function have been altered, both pre-and post-fire (Miller and Tausch, 2001;Briske et al., 2006; Petersen and Stringham, 2008). Ecological resilience may ...

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Abstract:Iron (Fe) deficiency is a yield-limiting factor for a variety of field crops across the world and generally results from the interaction of limited soil Fe bioavailability and susceptible genotype cultivation. Iron deficiency broadly occurs across the world in soybean, peanut, dry bean, sorghum, and rice but sporadically under unique or specialized conditions with corn, wheat, and oat. In this chapter, soil properties associated with the expression of Fe deficiency in field crops are defined, and biochemical interactions that promote field observed Fe-deficiency problems are explored. Strategies examined for use with field crops where Fe deficiency is a concern include cultivar selection and screening for tolerance, fertilizer and cultural practices, lowering soil pH, foliar sprays, chelated and complexed Fe fertilizers, concentrated fertilizers, mixed cultivar and companion crop interactions, and management of irrigation and drainage, fertility and seeding practices. Finally, we identify areas where future research is needed.

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High intensity wildfires in semiarid shrub and woodland plant communities can leave ecosystems incapable of self-repair and susceptible to weed invasion. Subsequently, land managers need effective restoration tools to reseed native vegetation back into these degraded systems. In order to develop successful post-fire restoration approaches in these communities, it is critical that we understand the mechanisms that impair reseeding success. Our objective was to quantify the influence of soil water repellency on seedling emergence and plant growth in a greenhouse study using soil cores obtained from beneath burned Juniperus osteosperma trees. Soil cores were seeded with either Elymus wawawaiensis or Agropyron cristatum, and watered with either a high (watered daily) or a low water regime (watered every 5 days). During the first watering event, water repellency was ameliorated in half the cores by adding a wetting-agent comprised of alkylpolyglycoside-ethylene oxide=propylene oxide block copolymers. Results showed that water repellency reduced seedling emergence and seedling survival by decreasing soil moisture availability. Wetting-agents improved ecohydrologic properties required for plant growth by decreasing runoff and increasing the amount and duration of available water for seedling emergence, survival, and plant growth. These results indicate that soil water repellency can act as an ecological threshold by impairing establishment of reseeded species after a fire. Where restoration efforts are limited by soil water repellency,