Competition for limited water supplies continues to restrict water available for irrigation. Irrigated agriculture must continually improve irrigation management to continue producing food, fiber, and fuel for a growing world population. Precision irrigation is the process of applying the right amount of water at the right time and place to obtain the best use of available water. Precision irrigation management is needed on large irrigation projects so water delivery matches irrigation needs and on individual fields to apply the right amount of water at the right time and place. Technology is commercially available to precisely apply water when and where crops need it; however, user-friendly decision tools are still needed to quantify specific irrigation needs and control water application within fields. Integrating information from various sensors and systems into a decision support program will be critical to highly managed, spatially varied irrigation.

The effect of tillage depth on physical properties in sandy soils under sugarbeet (Beta vulgaris L) is not well understood and documented. A 4-yr study was conducted to investigate the effect of zero tillage (ZT), shallow tillage (ST), and deep tillage (DT) practices on soil bulk density (BD), saturated hydraulic conductivity (Ks), and moisture content (MC) in a sandy loam. Undisturbed soil cores were collected at 0 to 10,10- to 20, 20- to 30, and 30- to 40 cm depths to measure BD and MC under each tillage practice. Soil Ks for the surface and subsurface layers were measured using a single head pressure ring infiltrometer and a constant head well permeameter, respectively. Soil BD was not significantly influenced by tillage in the 0- to 10, 10- to 20, 20- to 30, and 30- to 40 cm layers when averaged for four years. When averaged across the 0- to 40 cm depth, soil BD did not differ significantly among three tillages in 2008, 2009 and 2010; however, BD was significantly lower in DT (1.50 Mg m(-3)) than in ZT (1.61 Mg m(-3)) and ST (1.59 Mg m(-3)) in 2011. Soil BD averaged over all years and layers resulted in nonsignificant differences among three tillage practices. Soil Ks did not differ significantly among three tillage practices in 2008, 2009, and 2011 for the 0- to 40 cm depth. Similarly, soil Ks averaged across four years and four layers was not affected by tillage. In 2010, Ks was significantly greater in ST (27.60 mm h(-1)) than in ZT (17.21 mm h(-1)) and DT (12.46 mm h(-1)). Soil MC was not significantly influenced by tillage in any of the four depths when averaged across four years and when also averaged across four depths for each year. Across four years and four depths, averaged MC was not influenced by tillage. Large variations in Ks among ZT, ST and DT were likely caused by soil variability among replications within each tillage treatment. We concluded that tillage did not significantly affect BD, Ks and soil MC most likely due to the unchanging total porosity in sandy loam soil regardless of tillage type. (C) 2016 Published by Elsevier B.V.

Annual cereal forages are resilient in water use (WU), water use efficiency (WUE), and weed control compared with grain crops in dryland systems. The combined influence of tillage and management systems on annual cereal forage productivity and WU is not well documented. We conducted a field study for the effects of tillage (no‐till and tilled) and management (ecological and conventional) systems on WU and performance of forage barley (Hordeum vulgare L.) and weed biomass in two crop rotations (wheat [ Triticum aestivum L.]–forage barley–pea [ Pisum sativum L.] and wheat–forage barley–corn [ Zea mays L.] –pea) from 2004 to 2010 in eastern Montana. Conventional management included recommended seeding rates, broadcast N fertilization, and short stubble height of wheat. Ecological management included 33% greater seeding rates, banded N fertilization at planting, and taller wheat stubble. Forage barley in ecological management had 28 more plants m −2 , 2 cm greater height, 65 more tillers m −2 , 606 kg ha −1 greater crop biomass, 3.5 kg ha −1 mm −1 greater WUE, and 47% reduction in weed biomass at harvest than in conventional management. Pre‐plant and post‐harvest soil water contents were similar among tillage and management systems, but barley WU was 13 mm greater in 4‐yr than 3‐yr rotation. Tillage had little effect on barley performance and WU. Dryland forage barley with higher seeding rate and banded N fertilization in more diversified rotation produced more yield and used water more efficiently than that with conventional seeding rate, broadcast N fertilization, and less diversified rotation in the semiarid northern Great Plains.

Soil compaction has detrimental consequences on soil quality and plant root growth. Soil compaction is a variable property due to tillage in both space and time. A field study was conducted near Sidney, Montana in 2007 to evaluate spatial and temporal variations of soil penetration resistance (PR) on a 61-cm transect across the rows and inter-rows of sugarbeet on a clay loam in both conventional (CT) and strip tillage (ST) systems. A cone penetrometer was used to measure PR on a grid sampling scheme (5 cm horizontal x 2.5 cm vertical). The penetrometer was pressed into the soil every 5 cm along a 61-cm transect using a steel template bisecting the rows and inter-rows of sugarbeet. At each transect point, measurements were recorded at 2.5-cm depth increment to a depth of 30 cm. Soil PR measurements were recorded prior to planting (26 April), after the first cultivation (13 June), before harvest (3 October), and after harvest (4 October). Soil water contents were gravimetrically determined at the time of PR measurements. Soil PR was significantly greater in CT than in ST across the rows and inter-rows at the 0 to 30 cm depth for all sampling dates. Generally, soil PR increased with depth at every position on transect for all sampling dates under both tillage systems. Significant temporal variations in soil PR within each tillage system were observed throughout the growing season. Spatial variation data showed that less compaction was observed in crop rows compared to inter-rows under both tillage systems. Soil PR values increased as the growing season progressed and were highest prior to crop harvest, approaching values greater than 3.5 MPa below the soil surface.

Strip tillage (ST) and high‐efficiency overhead irrigation methods reduce fuel and water inputs compared to conventional practices, but have not been extensively evaluated in sugarbeet ( Beta vulgaris L.)–malt barley ( Hordeum vulgare L.) cropping systems. A field study comparing conventional tillage (CT) and ST systems and two sprinkler irrigation methods (mid‐elevation spray application, MESA; low‐energy precision application, LEPA) was conducted near Sidney, MT, from 2004 to 2008. Strip tillage was performed (for sugarbeet only) using a single operation that left alternating 30‐cm wide strips of tilled and untilled soil while fertilizer was simultaneously banded 10 cm below the seed row. Conventional tillage for sugarbeet consisted of six separate tillage operations following a broadcast application of fertilizer. Tillage preceding malt barley consisted of one pass each with a disk and a field cultivator following a broadcast application of fertilizer. Sugarbeet grown with ST yielded as well as when grown with CT. Irrigation method did not affect sugarbeet yield. Malt barley yield was not affected by irrigation method but was 5.4% lower following ST sugarbeet than when following CT sugarbeet. Tillage and fertilizer application costs for the sugarbeet phase of the 2‐yr rotation were estimated to be approximately $141 ha −1 less with ST than with CT representing reductions of 66% for the sugarbeet phase alone and 47% for the 2‐yr cropping system. It was concluded that both ST and LEPA are applicable to irrigated sugarbeet–malt barley cropping systems and may provide substantial cost savings compared to conventional practices.

Field drainage is a critical component of agricultural production in both arid and humid regions, but field drainage is often neglected and mismanaged as an important water resource. Innovative approaches for the integrated design and management of irrigation and subsurface drainage systems have tremendous potential to improve yields to help meet the rapidly emerging food demands and decrease total freshwater diversions to agriculture. Although irrigation system design and management have evolved tremendously in the past few decades, the design methodology and management criteria for subsurface drainage have not changed in the last 50years. Thus, all aspects of agricultural drainage require serious reconsideration and reevaluation to be able to meet emerging needs. This manuscript evaluates the current design criteria and practices and suggests viable alternatives for the improvement of subsurface agricultural drainage systems to meet the demands of modern agriculture. Drainage water treatment, reuse, and disposal are significant problems for agricultural drainage and various alternatives are presented. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Precision management of center pivot irrigated fields requires a knowledge of spatial variation within the field. Yield represents the integration of a multitude of processes taking place in the field, and is a reasonable place to begin to identify significant areas of variability. We mapped potato yields in five commercial center pivot fields (240 ha total size) in south central Washington using the HM-500 yield monitor developed by HarvestMaster, Inc. A pair of spread spectrum radio modems was used to transmit real-time yield data from the harvester to the mobile office. This allowed a real-time display of the raw yield data on the computer in the mobile office, permitting problems to be immediately detected without having to have an observer on the harvester. Substantial spatial variability of potato yields, both within and between fields was observed. The yield maps will be used to identify high and low yielding areas to focus further precision management research efforts.

Tillage can alter soil properties and affect crop yield and quality. A 4‐yr study was conducted on a Lihen sandy loam soil loam (sandy, mixed, frigid Entic Haplustoll) to evaluate the effect of tillage depth on sugarbeet (Beta vulgaris L.) root yield, root quality, and soil penetration resistance (PR). Tillage treatments consisted of no‐tillage (NT), shallow tillage (ST), and deep tillage (DT). Soil PR was measured with a penetrometer in 2.5‐cm increments to a 40‐cm depth at three locations within each plot. Roots were hand harvested from each plot and each sample consisted of roots of two adjacent rows. Sugarbeet root yield and adjusted sucrose yield were not significantly affected by the depth of tillage in 2008, 2009, and 2011. In 2010, root yield was significantly greater (16.5%) in DT than in NT. The average sugarbeet yields across 4 yr were 58.77, 60.30, and 63.03 Mg ha−1 for NT, ST, and DT, respectively. Root yield was lower in 2011 than other 3 yr due to cold and wet weather conditions in the spring. Soil PR values were significantly lower in DT than in ST and NT from 5‐ to 30‐cm depth. However, significant differences were found between ST and NT at the 5‐ to 7.5‐cm depth. Overall, DT enhanced soil physical environment but on average across 4 yr had no statistically significant effect on sugarbeet root yield and quality compared to both ST and NT practices, though a trend was noted that as tillage depth increased root yield increased.

One of today's greatest challenges of irrigated agriculture is to produce more food and fiber with less water, which can be accomplished by maximizing crop water productivity (CWP). A study was conducted to evaluate and compare the effect of conventional tillage (CT) and strip tillage (ST) on crop water use (CWU) and CWP of sugarbeet ( Beta vulgaris L.) on clay loam soil in the northern Great Plains (NGP). Seasonal CWU and CWP for sugarbeet root and sucrose yields were determined for the 2006, 2007, and 2008 growing seasons according to the water balance and CWP equations under CT and ST practices. No significant differences due to tillage were found for CWU of sugarbeet. In 2006, CWP for root yield was significantly greater in ST relative to CT due to wind damage early in the spring which reduced sugarbeet plant population in the CT. The mean CWP for root yield across three growing seasons was10% greater for ST than for CT due to the protected soil–plant environment under the ST. The ST greatly reduces wind erosion and the related plant damage. The ST system used 0.0093 m 3 and 0.061 m 3 of irrigation water less than CT system to produce 1 kg of sugarbeet root and 1 kg of sucrose yield, respectively, throughout the growing season. We concluded that ST can be used to produce sugarbeet root yield and CWP comparable to CT or even in some instances greater than CT in areas that are prone to wind damage to sugarbeet seedlings.

Brassicaceae oilseeds can serve as potential feedstocks for renewable biofuels to offset demand for petroleum-based alternatives. However, little is known about oilseed crop yield potential and N use in semiarid, wheat (Triticum spp.)-based cropping systems that dominate the northern Great Plains (NGP). A 5-yr study was conducted in northeast Montana to investigate the yield potential of a direct seeded system of durum (T. durum Desf.) in rotation with either chemical fallow or three Brassicaceae oilseeds: camelina [Camelina sativa (L.) Crantz], crambe (Crambe abyssinica Hochst. ex R. E. Fries), and canola-quality Brassica juncea L. Overall, results from the study indicated that seed yield in the three Brassicaceae oilseeds tested in rotation with durum was related (P < 0.001; r(2) = 0.68) to a nitrogen recovery index (NRI), indicating the importance of nitrogen use (NU) efficiency in dryland oilseed production, and that B. juncea generally used N more efficiently than crambe and camelina. Similarly, NRI was related (P < 0.001; r(2) = 0.72) to grain yield in durum following oilseeds. Grain yield of durum following B. juncea was similar to durum following fallow and greater than durum following camelina or crambe. Durum following crambe tended to use N more inefficiently than durum following camelina, B. juncea, or fallow. Differences in yield and N use of durum and oilseeds varied among years, which underscores the need to further develop management tools to optimize durum-oilseed cropping systems in highly variable rainfall environments typical of the NGP.

In recent years, there has been an increased global concern regarding the impact of soil compaction on crop production and soil quality in modern mechanized agricultural farming systems. Farm equipment is heavier than ever before, and many farmers have resorted to energy intensive deep tillage to alleviate compaction. Freeze-thaw processes influence the physical properties of soil, primarily soil compaction and structure. A 3-yr field study was established in fall 2009 to investigate the effects of the dynamics of freeze-thaw cycles (FTCs) on soil compaction in a clay loam. Results showed that frequent FTCs over the winter generally alleviated soil compaction at the 0- to 30-cm depth. During the winter of 2009-2010, soil penetration resistance (PR) in compacted treatments that were subject to freezing and thawing conditions was significantly reduced by 73, 68, and 59% at depths of 0 to 10, 10 to 20, and 20 to 30 cm, respectively. In compacted soils that were not subject to freezing, PR was significantly reduced by approximately 50, 60, and 46% at the same respective depths of the soil profile presumably due to the biology of soil and disruptive effects of shrink-swell cycles caused by frequent wetting-drying processes. These results demonstrate that repeated FTCs can alleviate soil compaction and alter soil physical quality. We conclude that FTCs associated with typical winter weather conditions are the most effective and economical way to alleviate soil compaction and improve soil structure through the dynamics of FTCs.

Depleted soil quality, decreased water availability, and increased weed competition constrain spring wheat production in the northern Great Plains. New management systems are necessary for improved crop productivity. The objective of our study was to compare productivity and soil water use of spring wheat (Triticum aestivum L.) in four crop rotations (continuous wheat, wheat–pea [Pisum sativum L.], wheat–forage barley [Hordeum vulgaris L.]–pea, and wheat–forage barley–corn [Zea mays L.]–pea) in two tillage (tilled and no‐till) and management systems (conventional and ecological). Conventional management included recommended seed rates, early planting date, and broadcast N fertilization. Ecological management included variable seed rates, delayed planting, banded N fertilization, and increased stubble height. Spring wheat in diversified rotations averaged 35 mm greater preplant soil water content, 37 mm greater water use, 0.8 kg ha−1 mm−1 greater water use efficiency, and 473 kg ha−1 and 817 kg ha−1 greater grain and biomass yields than continuous wheat. Wheat in conventional management averaged 28 fewer heads m−2, 4 additional seed head−1, and 2 mg seed−1 heavier seed weight than wheat under ecological management, resulting in 644 kg ha−1 greater yield. Wheat under ecological management used 8 mm more water, but water use efficiency was 2.6 kg ha−1 mm−1 greater under conventional management. Postharvest soil water content was similar among rotations, tillage, and management systems, suggesting that wheat uses most available soil water. Spring wheat in diversified rotations planted early in the season is more resilient and should confer greater production stability than continuous wheat systems planted late.

More than 20 years of private and public research on site-specific variable rate sprinkler irrigation (SS-VRI) technology on self-propelled center pivot and linear move irrigation systems has resulted in limited commercial adoption of the technology. Competing patents, liability, and proprietary software have affected industry's willingness to move into a new technology area. Documented and proven water conservation strategies using site-specific irrigation are quite limited. Marginal costs associated with site-specific technologies are high. Although sales of SS-VRI are increasing, they are primarily being used for eliminating irrigation and chemigation on non-cropped areas of a field or for land application of liquid agricultural and municipal wastes. Various aspects of SS-VRI technologies for general crop production are beginning to slowly gain widespread acceptance; however, their uses are largely focused on addressing symptoms of poor design and sub-optimal water and nutrient management. Although currently underutilized, SS-VRI technology has the potential to positively impact crop water productivity, water and energy conservation, and the environment. There are also few economic incentives to motivate growers to move to higher levels of SS-VRI management. Greater adoption rates will likely require higher costs for water and energy, severely restricted water diversions on a broad scale, and enforcement of compliance with environmental and other regulations. Sustainable use of SS-VRI will require strong research support, which is currently limited. In the short term, adoption of SS-VRI technologies will be enhanced by addressing equipment deficiencies and research developing basic criteria and systems for defining management zones and locations of various sensor systems for both arid and humid regions. Training adequate personnel to help write site-specific variable rate irrigation prescriptions in humid and arid areas to assist growers with the decision-making process is also a high priority. There is also a large need to educate government boards and bankers on the potential benefits of these systems. The long-term challenges will be to demonstrate that SS-VRI will improve water management or increase net returns. There is a critical need to develop fully integrated management systems with supporting elements that accurately and inexpensively define dynamic management zones, sense within-field variability in real time, and then adaptively control site-specific variable rate water applications, which will be challenging as significant knowledge gaps exist.