Jeffrey S. Jacobsen

Response of Malt Barley to Phosphorus Fertilization Under Drought Conditions

ABSTRACT Drought conditions are common in the northern Great Plains of the United States, affecting crop yield and quality. Phosphorus (P) fertilizer applications have been found to increase drought tolerance, although there is a lack of published work in this area. The goal of this study was to determine the effects of P fertilization on drought tolerance in malt barley (Hordeum vulgare). Here, 60 cm tall PVC columns were filled with either a silt loam that had a medium soil test phosphorus (STP) level or with the same soil diluted 1:1 (v/v) with coarse sand (low STP). Monoammonium phosphate was incorporated into the surface soil at rates equating to 0, 7.5, and 25 kg P ha− 1 (in triplicate), seeded with malt barley, and watered to maintain water contents either slightly above –1.5 MPa (dry treatment) or slightly drier than field capacity (wet control). Fertilization with P significantly increased plant biomass, root biomass, grain yield, and water-use efficiency (WUE) in the medium STP soil, but not in the low STP soil. Growth in the low STP, coarse, dry soil was apparently limited by water, not P, based on comparisons with the wet control. Fertilization of the dry medium STP soil with P increased grain yield by at least 20-fold, although this increase was not significant due to high variability. These results suggest that adequate soil P levels can substantially offset the impact of drought on barley growth and grain yield.

Effect of Low‐Rate Commercial Humic Acid on Phosphorus Availability, Micronutrient Uptake, and Spring Wheat Yield

Abstract A greenhouse study was conducted to determine the effects of low‐rate commercial humic acid (HA) on phosphorus (P), iron (Fe), and zinc (Zn) availability and spring wheat yields, in both a calcareous soil and a noncalcareous soil. In Phase I, soluble P concentrations were monitored at 1.9, 3.8, and 5.7 cm from a monoammonium phosphate (MAP) fertilizer band that had either been coated with one of two HA products at the equivalent of 1.7 kg HA ha−1, a label rate, or left uncoated. Sampling occurred periodically up to 48 d after fertilizer application. In Phase II, uptake of P, Fe, and Zn and grain yield were measured in soils that had been fertilized with 7.5 or 25 kg P ha−1, either coated with HA or left uncoated. In Phase I, only three significant differences (P=0.05) out of 66 comparisons were found in soluble P concentrations between HA and control treatments at time points ranging from 4 to 48 d after fertilization. In addition, no significant differences were found in nutrient uptake, shoot biomass, or grain yield between HA and control treatments. These greenhouse results suggest that low commercial HA rates (∼1.7 kg HA ha−1) may be insufficient to enhance spring wheat growth.

Metal concentrations in three Montana soils following 20 years of fertilization and cropping

The presence of metals in some agricultural fertilizers has raised the concern that fertilized soils may be accumulating potentially toxic metals. A number of studies have been undertaken to determine the extent and significance of this potential problem, yet results have been mixed and the studies were not conducted in the Northern Great Plains. Therefore, a study was undertaken to determine if fertilization has increased metal concentrations in selected Northern Great Plain soils. Two irrigated sites and one non-irrigated site were selected; each had at least 20 years of fertilization and cropping history. Paired (fertilized and non-fertilized) soils from three depths (0–15 cm, 15–30 cm, and 30–45 cm) were sampled in replicate (n=10) and analyzed for a range of plant available and total metals, pH, organic matter, and phosphorus. In general, fertilized soils were found to have significantly lower levels of available and total metals than those of non-fertilized soils, indicating that long-term fertilization has not increased metal concentrations in the soils studied.

Stratification of soil acidity derived from nitrogen fertilization in winter wheat tillage systems

Abstract Conservation tillage systems have varying degrees of mechanical soil mixing which may result in stratification of soil properties. This study was conducted to determine the change in soil acidity due to surface N applications (0, 56, 112,168, 224, and 280 kg N/ha) in recently initiated continuous winter wheat (Triticum aestivum L.) clean‐till (CT), reduced‐till (RT), and not‐ill (NT) systems. Experiments were conducted three consecutive years on Grant silt loam (fine‐silty, mixed, thermic Udic Argiustoll) and Norge clay loam (fine‐silty, mixed, thermic Udic Paleustoll) soils. Soil samples were taken after harvest and separated into 0 to 2.5, 2.5 to 7.5, 7.5 to 15, 15 to 30, and 30 to 60 cm depth increments after the second, third, and fourth cropping seasons. Reduced‐till and NT systems developed increased acidity in the top 7.5 cm of soil compared to CT. Tillage system trends were not expressed as dramatically as the N contribution to soil acidification. Application of only 56 kg N/ha significan...

Sap analysis for diagnosis of nitrate accumulation in cereal forages

Abstract Development of a quantitative, preharvest quiektest for NO3 levels in cereal forages would improve crop management options to avoid NO3 toxicity in livestock. Our objective was to determine if concentrations of NO3 in sap expressed from oat (Avenasativa) and barley (Hordeum vulgare) are correlated with those in dry tissue of simultaneously harvested hay, and to test the reliability of the Cardy portable NO3 meter for sap analysis in these species. In 1993, whole plant samples were gathered from plots fertilized with variable nitrogen (N) rates at four environments in Montana, and were analyzed for NO3 concentration in lower‐internode sap and in whole plant dry matter. In 1994 and 1995, the study was repeated at two environments. The sampling technique included three subsamples from each plot for sap analysis, followed immediately by harvest of the entire plot for hay, and further subsampling for dry matter NO3 analysis after drying. Linear correlations between dry matter and sap NO3 concentration...

Spring Wheat Response to Fertilizer Placement and Nitrogen Rate with Limited Moisture

Abstract Plant response to fertilizer placement under dryland conditions is dependent upon interactions between moisture, the crop, and root access to applied fertilizer. This study was conducted to determine response of spring wheat (Triticum aestivum) to fertilizer placement and nitrogen (N) rate under limited moisture conditions in a conservation tillage system. Field trials were conducted over a three‐year period, from 1987–1989, with broadcast and band fertilizer placements applied at the recommended N rate or at 1.5X this rate, all with a uniform application of P, K, and S in a randomized complete block design. Banded fertilizer stimulated plant growth early in the growing season (Feekes 5–6) and produced dry matter with increased N and P concentration and content. As drought conditions developed over the course of the growing season, grain yield differences due to fertilizer placement and N rate diminished. There were, however, straw yield increases at harvest with band fertilizer placement. Early ...

Variation in soil fertility test results from selected northern great plains laboratories

Soil analytical labs play an important role in agricultural nutrient management. However, variability between labs can undermine the perception of soil testing efficacy and possibly lead to inaccurate fertilizer recommendations. To compare standard soil analysis results from labs commonly used by Montana producers, soil samples from four different sites were sent anonymously to up to ten labs over a three year period, with three submissions per year. Variability within labs and between labs was observed, and is at least partially linked to different laboratory methods or changes in laboratory methods during the study period. Several labs showed a trend of improving lab repeatability. The results suggest that agricultural professionals should choose their labs wisely, specify analytical methods, and review results critically. In addition, the analytical data reported, and ultimately, the fertilizer recommendations provided, should be considered guidelines to nutrient management to be tailored to site-specific conditions.

Alfalfa/grass response to nitrogen and phosphorus applications

Abstract Alfalfa/grass (Medicago sativa/Dactylis glomerata, Bromus) yield and quality responses to nitrogen (N) and phosphorus (P) fertilizer applications are well documented. The magnitude of the P response and in turn N, may however, be limited by the relative immobility of P in the soil. A two‐year field study was conducted to determine the response of an established alfalfa/grass stand to combinations of a one‐time broadcast application of N, P, and sulfur (S) rates with fall or spring applications of P. Nitrogen and P applications increased forage production, nutrient concentration and nutrient content, particularly in the first production year. No S response was observed. Fall P applications were superior to spring applications only in the first year of production. If annual broadcast applications of P are made to existing alfalfa/grass stands in Intermountain areas, fall applications are recommended.

Reduced-till spring wheat response to fertilizer sources and placement methods

Abstract Field studies were conducted to determine the effect of nitrogen (N) and phosphorus (P) fertilizer sources and placement configurations on spring wheat growth, yield and quality. Different standard and experimental N and P sources at two rates and in different placement methods provided 32 fertilizer treatments at three locations. Banding of N and P together resulted in the greatest yields. Of the fertilizer combinations where N and P were applied separately, only broadcast N with deep banded P gave similar yields to N and P together. Banding fertilizer with the seed at these levels damaged seedling growth and limited yield. Elevated protein levels, when found, were likely due to lower yields and subsequent concentration of N in grain protein. Careful consideration of fertilizer rate, source and placement strategies to optimize production and water utilization are essential in dryland environments.

Mapping soil attributes for site-specific management of a Montana field

Conventional soil maps represent the distribution of soil attributes across landscapes but with less precision than is needed to obtain the full economic and environmental benefits of site- specific crop management. This study quantifies the spatial variability of three agronomically significant soil attributes: (1) thickness of mollic epipedon, (2) organic matter content (OM), and (3) pH as related to soil survey map units, spectral data, and terrain attributes for a 20 ha field in Montana. Analysis of Order 1 (1:7920-scale) Soil Survey map units indicates substantial variation in all three soil attributes. There was some evidence that similar attribute values were clustered in the field (0.40 - 0.46 Morans Coefficients). Two spectral band ratios explained 64% of the variation in OM across the field. GPS/GIS-derived wetness index, sediment transport index, elevation, and slope gradient explained 48% of OM variation. Wetness index, slope gradient, and plan curvature combined to explain 48% of the variation in mollic epipedon thickness. Elevation and wetness index explained just 13% of pH variation. Two spectral band ratios, specific catchment area, and wetness index combined to explain 70% of the variation in OM at 66 sampling sites. Four contour map representations of OM illustrate the sensitivity of the final maps to variations in input data and interpolation method.