Bruce L. Webb

Recovery Patterns of Cryptogamic Soil Crusts in Desert Rangelands Following Fire Disturbance

The effects of fire on cryptogamic soil crust communities at Camp Floyd State Park, Utah, were examined. Three years after fire, lichen and moss cover were both substantially lower in abundance in the burned area than in the adjacent unburned area. Both the living algae, as measured by culture techniques, as well as the subfossil diatom commi nity, which was measured directly, were also significantly lower in the burned area. Two years later, the algae had shown considerable recovery. Only one group of algae, the chrysophyte cysts observed in the subfossil diatom slides, was significantly lower in the burned area at this time. Though invasion of lichens and mosses had begun after five years, recovery was not complete either in terms of biomass or composition at the conclusion of the study. Factors contributing to the recovery of the crusts ap- parently included above average precipitation over the last few years, proximity and type of prop- agules, and protection from subsequent disturbance.

Pelletized cyanobacterial soil amendments: Laboratory testing for survival, escapability, and Nitrogen fixation

The escape and growth of Microcoleus vaginatus from alginate pellets onto soil crusts under controlled laboratory conditions were examined. Soil crust samples were collected and placed in petri dishes. Selected samples were sterilized, and three treatmerits were established: 75 g m−2 Microcoleus pellets added to sterilized soil, 75 g m−2 blank pellets added to sterilized soil, and unsterilized soil with no additions. Chlorophyll a readings were significantly higher in unsterilized soils. Microcoleus biovolumes were highest in sterilized inoculated soils and significantly higher than sterilized untreated soils. Microcoleus filament density was significantly higher in Microcoleus‐inoculated soils than in the other two treatments. Nitrogen fixation activity was recorded in unsterilized soils after only 1 month, and rates increased as the experiment progressed. Microcoleus‐inoculated soils had significant nitrogen‐fixing activity during the last sampling period.

PHOSPHORUS AND MANGANESE INTERACTIONS AND THEIR RELATIONSHIPS WITH ZINC IN CHELATOR-BUFFERED SOLUTION GROWN RUSSET BURBANK POTATO

Manganese (Mn)- and zinc (Zn)-driven antagonistic interactions with high available phosphorus (P) can result in negative impacts on potato cropping systems. Two chelator-buffered hydroponic experiments were conducted with Russet Burbank potato to elucidate P and Mn relationships and associated interactions with Zn. In both experiments, a P concentration decline in new shoots, old shoots, and roots resulted as solution Mn changed from deficient to sufficient followed by a P concentration rise as solution Mn changed to excessive concentrations. New and old shoot Zn concentrations generally increased with augmented solution Mn in the variable Mn experiment, but no significant changes were found in root Zn contents. Available Mn was observed to control plant P concentrations and to influence Zn uptake and translocation; thus, Mn has considerable impact on uptake and distribution of P and Zn and on P-Zn interactions in potato.

PHOSPHORUS AND ZINC INTERACTIONS IN CHELATOR-BUFFERED SOLUTION GROWN RUSSET BURBANK POTATO

High phosphorus (P) application in potato production potentially leads to antagonistic interactions with cationic micronutrients. None of the nine combinations of phosphorus and zinc (Zn) provided in chelator-buffer solution for 17 days to potato supported the concept of a P-induced Zn deficiency with regard to early season dry matter yield, especially when solution P ranged from sufficient to excessive—conditions under which P-Zn interaction traditionally is observed. Increased solution P at low Zn levels resulted in a steep increase of P in new and old shoot growth and an accumulation of manganese (Mn) in potato roots—a combination that might indirectly impact Zn nutrition in potato. Although high P levels in potato did not directly reduce Zn content or cause Zn deficiency, excessive P accumulation may reduce the activity of Zn by interacting with other micronutrients such as Mn.

PHOSPHORUS AND ZINC INTERACTIONS AND THEIR RELATIONSHIPS WITH OTHER NUTRIENTS IN MAIZE GROWN IN CHELATOR-BUFFERED NUTRIENT SOLUTION

Maize (Zea mays L.) is common in potato (Solanum tuberosum L.) cropping systems and is especially susceptible to zinc (Zn) deficiency, possibly related to induced potato demand for high phosphorus (P). Three chelator-buffered nutrient solution experiments were evaluated for maize response to establish ranges of deficient, sufficient, and excessive Zn and P and to evaluate interactions. Zinc concentrated in roots and manganese (Mn) accumulated in shoots as P increased, but only 32 μM P produced significantly lower shoot Zn than other treatments and there was not a decline in shoot Zn at high P levels. Deficient Zn levels promoted excessive P uptake. Root Mn increased dramatically above 0.05 μM Zn, peaked at 20 and 40 μM Zn, and then declined at higher solution Zn levels. The P-Zn interaction in maize may be explained by the combined impacts of increased available P on Zn precipitation in roots and increased Mn in shoots.

A pressurized hot water extraction method for boron

Extracting boron (B) to predict plant availability in arid soils is a tedious soil test procedure, and an inexpensive, rapid alternative would be welcomed. This paper compares the results of tests conducted with pressurized hot water and conventional boiling hot water extraction of soil B. The time required for pressurized hot water extraction varied with each soil, but averaged 1.0 min per sample compared 10 min per sample for the standard boiling hot water technique. A Maxim EX-450 model espresso machine producing water at 90°C was used to extract B from 40 arid zone soils. Resulting aliquots were analyzed by ICP spectrometry. The measured values of B with pressurized hot water extraction were higher than with the boiling hot water extraction. There was a high and significant correlation between B values using the boiling hot water extraction and the pressurized hot water extraction [r=+0.83 (p=0.001)]. A regression equation y=0.12217+0.21155x (r 2=68) (y is mg kg− 1 boiling hot water extractable B and x is mg kg− 1 pressurized hot water extractable B) converts pressurized hot water readings to standard values already correlated with field response. Also tested were three espresso machines from different manufacturers (Krups, Mr. Coffee and Maxim) testing five widely divergent soils and found similar B extraction with each espresso machine. This pressurized hot water extraction procedure provides a much needed simplification for measuring B in soils, but currently the concentration must be determined with ICP rather than colorimetric measurement because of color interference.

OPTIMIZING PHOSPHORUS AND ZINC CONCENTRATIONS IN HYDROPONIC CHELATOR-BUFFERED NUTRIENT SOLUTION FOR RUSSET BURBANK POTATO

High rates of phosphorus (P) fertilizer for potato production have potentially negative environmental and nutritional consequences, including antagonistic interactions with micronutrients. Variable P or zinc (Zn) treatments were evaluated in chelator-buffered solutions to identify deficient, sufficient, and excess concentrations for Russet Burbank potato. Visual observations, dry matter, and nutrient concentrations confirmed 0.1 and 2 μM as deficient, 6 to 54 μM as sufficient and 162 and 456 μM Zn as excessive under variable Zn; and 32 μM as deficient, 64 to 512 as sufficient and 1024 and 2048 μM P as excessive under variable P. A strong impact of solution Zn on P concentration and almost no impact of solution P on Zn concentration of potato were observed. New and old shoot and root Mn concentrations were affected by solution P. Results facilitate further study of P-Zn interactions using the chelator-buffered solution.

ZINC, MANGANESE AND PHOSPHORUS INTERRELATIONSHIPS AND THEIR EFFECTS ON IRON AND COPPER IN CHELATOR-BUFFERED SOLUTION GROWN RUSSET BURBANK POTATO

Three hydroponic experiments were conducted with Russet Burbank potato to elucidate zinc (Zn) and manganese (Mn) relationships and associated interactions with other nutrients at different levels of phosphorus (P). Except when P was optimal, root Mn concentration was reduced at optimal solution Zn relative to deficient or excessive Zn levels. Shoot Mn generally increased with augmented solution Zn. As solution Zn increased, root P declined while shoot P and copper (Cu) and root iron (Fe) and Cu increased. Increasing solution Mn generally decreased Zn in all plant tissues—especially in roots. The Mn influence on plant P, Cu, and Fe concentrations was nearly opposite the Zn impact, indicating that Zn and Mn have counter effects. Partitioning between root and shoot micronutrient concentrations occurred when available P was either deficient or excessive, which may also help explain poor plant health and adverse micronutrient relationships in potato when available P is not optimally maintained.

Pressurized Hot Water and DTPA‐Sorbitol as Viable Alternatives for Soil Boron Extraction. I. Boron‐Treated Soil Incubation and Efficiency of Extraction

Abstract Serious challenges associated with hot water extraction, the standard extraction method for water‐soluble boron (B), limit its use in commercial soil‐testing laboratories. Several alternatives to make B testing more practical have been proposed and studied; none of the alternatives have readily replaced the hot water method. Two relatively new, promising B extraction methods are pressurized hot water and DTPA‐Sorbitol. Very little reported work compares B extraction values obtained from the standard hot water extraction method and these two alternative methods. This study was conducted to complete an initial step in validating new procedures—extracting the designated nutrient from fertilized, incubated soils by using standard and alternative extraction methods and comparing the resulting values. The three extraction methods were used to extract B from samples of calcareous sand and silt loam soils and limed, loamy fine sand, all which had been treated with 10 levels of B (0–8 mg kg−1) and incubated for 7 and 28 days. The amount of B extracted increased as the rate of B application increased with all three soil‐extraction methods. High correlations (r 0.977–0.999) were observed between extractable B and rate of B application with all three procedures. Correlations between the amount of extractable B using hot water extraction and the value obtained with an alternative extraction method were similar for both methods (r=0.89). Hot water generally extracted the least and pressurized hot water the most B regardless of soil type, rate of application, or duration of incubation. This study suggests the more easily used methods of pressurized hot water and DTPA‐Sorbitol could be recommended as replacements to the cumbersome hot water extraction.

A comparison of hot water extraction to standard extraction methods for nitrate, potassium, phosphorus, and sulfate in arid‐zone soils

Abstract Increasing demand for soil analysis prompted by environmental and economic factors has intensified the need for an inexpensive, fast, convenient and precise extraction. Current soil analysis procedures require several extractants which limit their use in many small commercial and residential applications. This paper reports the results of tests conducted with an innovative hot water extraction method to meet these needs in the soils of the arid Western United States. Hot water under pressure generated by commonly available espresso makers was used, with an appropriate proper soil/water ratio, to extract nitrate, potassium (K), sulfate, and phosphorus (P) in as many as 38 soils. The same extract was also used to measure pH. There were high and significant correlations when comparing standard soil analysis extraction methods and the hot water extraction for nitrate, sulfate, K, and P [r=0.99, 0.92, 0.85, and 0.60, respectively (p=0.001)]. The time of extraction varied with each soil, ranging from 0...