Dan S. Long

Active ground optical remote sensing for improved monitoring of seedling stress in nurseries.

Active ground optical remote sensing (AGORS) devices mounted on overhead irrigation booms could help to improve seedling quality by autonomously monitoring seedling stress. In contrast to traditionally used passive optical sensors, AGORS devices operate independently of ambient light conditions and do not require spectral reference readings. Besides measuring red (590–670 nm) and near-infrared (>760 nm) reflectance AGORS devices have recently become available that also measure red-edge (730 nm) reflectance. We tested the hypothesis that the additional availability of red-edge reflectance information would improve AGORS of plant stress induced chlorophyll breakdown in Scots pine (Pinus sylvestris). Our results showed that the availability of red-edge reflectance information improved AGORS estimates of stress induced variation in chlorophyll concentration (r2 > 0.73, RMSE < 1.69) when compared to those without (r2 = 0.57, RMSE = 2.11).

Mapping straw yield using on-combine light detection and ranging lidar

Wheat (Triticum aestivum L.) straw is not only important for long-term soil productivity, but also as a raw material for biofuel, livestock feed, building, packing, and bedding. Inventory figures in the USA for potential straw availability are largely based on whole states and counties. Site-specific information is needed to determine where sufficient straw is available for removal within farm fields. The objective of this study was to assess the accuracy and feasibility of light detection and ranging (lidar) measurements of crop height for predicting the straw yield of wheat at site-specific field locations and apply this information to determining where excess straw is available beyond soil conservation needs. An inexpensive lidar sensor was mounted on the top of a Case International Harvester 1470 combine and aimed to point forwards at a 45° angle over the combines reel. Lidar-measured crop height was correlated with manually measured crop height in small plots (r 2 = 0.79) and was a good predictor of straw productivity across three farm fields (r 2 = 0.85). Crop height was better correlated with straw yield than grain yield or grain protein concentration. Crop height predicted by lidar could then be used to estimate straw yield from a predetermined linear relationship between crop height and straw yield. A straw yield map was generated during harvest by programming the lidar sensor to compute the average of 91 readings in each scan. A map of harvestable straw was computed by subtracting the amount of straw required to maintain soil organic carbon from a map of total straw yield. Lidar is potentially useful for measuring crop biomass on a combine harvester and determining where in farm fields excess crop residue can be removed for commercial purposes. Further work with lidar is needed to resolve the issue of flying chaff.

Grain protein as a post-harvest index of nitrogen status for winter wheat in the northern Great Plains

The use of grain protein as a post-harvest index of N fertility status has been promoted for spring wheat (Triticum aestivium L.) through the establishment of critical levels for segregating wheat into N deficient vs. N sufficient classes. The objectives of this study were to evaluate this concept for winter wheat in the northern Great Plains; and to estimate the added N requirements necessary to achieve maximum yield when protein concentrations fall below the critical level. A field study consisting of three water regimes, four cultivars, and five fertilizer N levels was conducted near Havre, MT. A consistent relationship between relative yield and grain protein was found and a critical protein concentration of 121 mg g-1 was defined using Cate-Nelson R2 statistics. Protein concentrations below the critical level were associated with yield losses from N deficiency (79% frequency), while protein concentrations ≥ the critical level were associated with N sufficiency (93% frequency). Under conditions of mod...

On-Combine Sensing and Mapping of Wheat Protein Concentration

Site-specific measurements of grain protein concentration, in addition to grain yield, are potentially useful for assessing spatial variability in cereal crop production as needed in precision agriculture. This study investigated an on-combine spectroscopic sensor for mapping grain protein levels within farm fields. The optical, near-infrared sensor was calibrated in the laboratory to test samples of hard red spring wheat (r 2 = 0.99, SEC = 0.081%). Grain protein data for spring wheat were then acquired for a 45-acre dryland wheat field, and compared with test samples that had been manually sampled from the combine’ s exit auger. The ability of the sensor to predict protein values declined in the field (r 2 = 0.55, SEP = 0.66%). However, a map of grain protein concentration derived from on-combine sensing was highly correlated with a test map of grain protein (r = 0.93). The results are sufficiently promising to suggest that on-combine spectroscopic sensing of grain protein concentration for mapping purposes is technically feasible.

Evaluation of methods to determine residual soil nitrate zones across the northern Great Plains of the USA

A four-year study was conducted from 2000 to 2004 at eight field sites in Montana, North Dakota and western Minnesota. Five of these sites were in North Dakota, two were in Montana and one was in Minnesota. The sites were diverse in their cropping systems. The objectives of the study were to (1) evaluate data from aerial photographs, satellite images, topographic maps, soil electrical conductivity (ECa) sensors and several years of yield to delineate field zones to represent residual soil nitrate and (2) determine whether the use of data from several such sources or from a single source is better to delineate nitrogen management zones by a weighted method of classification. Despite differences in climate and cropping, there were similarities in the effectiveness of delineation tools for developing meaningful residual soil nitrate zones. Topographic information was usually weighted the most because it produced zones that were more correlated to actual soil residual nitrate than any other source of data at all locations. The soil ECa sensor created better correlated zones at Minot, Williston and Oakes than at most eastern sites. Yield data for an individual year were sometimes useful, but a yield frequency map that combined several years of standardized yield data was more useful. Satellite imagery was better than aerial photographs at most locations. Topography, satellite imagery, yield frequency maps and soil ECa are useful data for delineating nutrient management zones across the region. Use of two or more sources of data resulted in zones with a stronger correlation with soil nitrate.

Spectral indices for yellow canola flowers

Reproductive growth, such as by flowers, may contribute to a canopy-level signal yet there are no current indices that measure variation in flowering. This study was conducted to determine how flowers influence the overall canopy signal and what bands of light may be useful for estimating variation in flower density and leaf area index (LAI). The effects of the number of yellow flowers per unit area and LAI on canopy spectral reflectance of spring canola (Brassica napus L.) were investigated in a field study consisting of three water regimes and three fertilizer nitrogen levels near Pendleton, Oregon, USA. A band ratio of green and blue light was strongly (r2 = 0.87) related to the number of yellow flowers per unit area, whereas a ratio of near-infrared and blue light was most suitable for estimating LAI during flowering. Spectral information during flowering may improve how remote sensing is used to describe plant development and reproductive capacity during the growing season.

On-combine, multi-sensor data collection for post-harvest assessment of environmental stress in wheat

On-combine yield monitors are widely used in precision agriculture for locating areas within fields where yields are reduced. However, the crop yield variability may be better interpreted by utilizing grain protein maps to reveal the factors limiting yield. The objective of this study was to develop an on-combine multi-sensor system for obtaining site-specific measurements of grain yield, grain protein concentration, and straw yield at the same spatial resolution as grain yield. The methodology is based on a mass flow yield monitor, in-line near-infrared spectrometer, and light detection and ranging (LiDAR) instrument. The LiDAR sensor is used to indirectly estimate straw yield through the measurement of crop height. Neighborhoods within the individual grain yield and protein maps obtained by the yield monitor and the protein sensor are correlated to identify areas within fields where grain yield was limited by nitrogen stress or water stress. In addition, scatter plots of grain yield and straw yield, and deviations from the observed maximum slope, are used to identify specific regions of environmental stress. Multi-sensor data are acquired at coincident locations and thus, it is not necessary to interpolate data to a common estimation grid to enable their fusion. The on-combine, multi-sensor system is illustrated with results from farm fields in eastern Oregon, USA.

Spring Wheat Production and Associated Pests in Conventional and Diversified Cropping Systems in North Central Montana

Producers in the northern plains are diversifying and intensifying traditional wheat (Triticum aestivum L.)-based cropping systems by reducing summer fallow and including legume and oilseed crops. This study examined the influence of diversification and intensification on spring wheat yield and quality and associated insects, diseases, and weeds. Research was conducted during the 1998 through 2000 period in farm fields in north central Montana. Conventional rotations included either hard red spring wheat–spring barley (Hordeum vulgare L.)–fallow or spring wheat–fallow. Diversified rotations included replacement of fallow with either annual pulse crops or cool-season oilseeds. Preplant soil water was less in diversified rotations, but residual nitrate was not influenced by rotation type. Insect pests and beneficial arthropods were in greater numbers in conventional rotations. Incidence and severity of crown and root rots of wheat were similar between rotation types, but foliar leaf spot diseases were greater for wheat in conventional rotations. Weed densities were not influenced by rotation type. Spring wheat yield, tiller density, and test weight were greater in conventional rotations. Spring wheat in diversified rotations had greater drought stress. Diversification and intensification of spring wheat systems may reduce pests and decrease wheat productivity, particularly when precipitation is inadequate.

Effect of Planting Methods on Spring Canola (Brassica napus L.) Establishment and Yield in the Low-Rainfall Region of the Pacific Northwest

Growers are becoming interested in producing canola (Brassica napus or B. rapa) in the dryland, wheat-fallow region of the Pacific Northwest. Currently, agronomic research for spring canola in this region has not been initiated. This study evaluated the effect of no-till planting methods on stand establishment, crop yield, and seed oil quantity of spring canola in Washington and Oregon in 2009 and 2010. The treatments included: double disk opener; broadcast; broadcast plus rolled; Kile opener; Cross-Slot opener; and hoe opener (at Washington only). In this study, canola establishment was generally greatest with the double disk opener and least in the broadcast or broadcast plus rolled treatments at all four site-years. Yield was least in the broadcast treatment and rolling broadcast seed increased yield only 50% of the time. In three out of four site-years, canola planted with the various no-till openers yielded higher than broadcast seed. The adoption of spring canola in the wheat-fallow region of the Pacific Northwest would improve pest management strategies, diversify markets, and increase sustainability.

Intensive Crop Rotation Yield and Economic Performance in Minimum Tillage and No Tillage in Northeastern Oregon

In the intermediate annual precipitation zone (14 to 18 inches) of northeastern Oregon, there is interest in increasing the intensity of cropping with spring crops. Mechanical tillage remains popular for seedbed preparation and weed control, but contributes to environmental problems and high labor and fuel cost. No-tillage (NT) crop production can reduce on site and off site problems and has lower labor and fuel costs, but soil-borne disease and weed control problems can limit yields. We compared crop yields, production costs, and economic returns of an intensive, four-year crop production rotation under two management systems: (i) minimum tillage (MT) with cultivation by chiseling, sweeping, and rod weeding; and (ii) NT with chemical weed control. The rotation was fallow-winter wheat-dry spring peawinter wheat in which a spring broadleaf crop is included to aid in the control of winter annual weeds and reduce host pathogen levels of soil-borne cereal diseases. Four year averages of wheat yields in the NT treatment were equal to or greater than those in the MT treatment whereas dry green pea production was roughly equal in each treatment. Crop productivity differed significantly in each phase of the rotation in descending order from winter wheat following fallow [4,578 lb/acre (76 bu/acre)], winter wheat following dry spring pea [3,548 lb/acre (59 bu/acre)], to dry spring pea (1,505 lb/acre). Partial budget analysis shows that NT is substantially less costly than MT in terms of labor and fuel, potentially making NT economically viable for intensive cropping systems in the intermediate precipitation dryland region of northeastern Oregon.