Dan Drost

Ammonium-loaded clinoptilolite : A slow-release nitrogen fertilizer for sweet corn

Abstract Nitrogen (N) loss from irrigated cropland, particularly sandy soils, significantly contributes to nitrate (NO3 ‐) contamination in surface and ground waters and increases N applications to crops. Ammonium‐loaded clinoptilolite (A‐Cp) may reduce N leaching from sandy soils while sustaining plant productivity. We conducted two greenhouse plant growth experiments with sweet corn (Zea mays L.). Pots containing a sandy soil planted with sweet corn were fertilized with either ammonium sulfate (AS) or one of three size fractions of A‐Cp, small (<0.25 mm), medium (0.25 to 2 mm), or large (2 to 4 mm), at rates of 112, 224, or 336 kgN ha‐1 (Experiment #1) and 112 or 224 kg N ha‐1 (Experiment #2). We compared ammonium (NH4 +) and NO3 ‐ leaching from these pots and compared corn relative growth rates (RGR), leaf area ratio (LAR), and net assimilation rate (NAR) among all N fertilizers. Soil amended with AS leached 10 to 73% of the added N, depending on N rate, whereas <5% of the added N leached from the A‐Cp...

Soil water deficits and asparagus : II. Bud size and subsequent spear growth

Abstract Soil moisture stress in one year may negatively affect spear growth in the following year. We tested this hypothesis by applying soil water potentials (SWP) of −0.05, −0.3, or −0.5 MPa to asparagus plants and evaluated the effects of prior SWP history on bud size and spear growth assessed under ideal growing conditions. Total and viable bud numbers decreased linearly as SWP decreased. Although bud diameter within a bud cluster was variable, in general, as SWP decreased bud diameter decreased. SWP history had no effect on harvested spear number though total spear weight was less in the −0.3 MPa SWP than in the −0.05 or −0.5 MPa. Spear elongation rates were similar for all SWP and averaged 0.029 mm/h. Spear diameter distributions were significantly affected by SWP history. Chi-square test for the −0.05, −0.3, and −0.5 MPa were 6.6, 12.0, and 23.4, respectively, with increasing values indicating a departure from the expected distribution of spear diameters. Results indicate that SWP near field capacity are needed for optimum asparagus spear size and yield.

Soil water deficits and asparagus: I. Shoot, root, and bud growth during two seasons

Abstract Although considered to be drought tolerant, asparagus has been shown to respond to supplemental irrigation. Asparagus plants were dried to soil water potentials (SWP) of −0.05, −0.3 or −0.5 MPa before irrigating during two seasons in a greenhouse. SWP were applied for four months and then crowns were stored to simulate dormancy. After storage, crown re-growth was assessed, followed by re-initiation of the SWP. In the second year, the −0.05, −0.3, and −0.5 MPa treatments were nested in the first years SWP (total nine SWP treatments) to test the response of asparagus growth to prior SWP history. In both years, during the SWP period, whole plant harvests were made monthly and growth evaluated. In the first year, as SWP decreased, fern number and dry weight, storage root number and dry weight and bud numbers decreased linearly regardless of the harvest date. Storage had no effect on storage root number, though total root dry weight decreased during storage in all SWP. In the second year, fern, storage root, and bud numbers and root dry weight corresponded to the 1988 SWP regardless of the 1989 SWP early in the year. However, as the second growing season progressed, storage root and bud numbers and plant dry weights decreased linearly as SWP decreased and reflected the influence of the 1989 SWP. When supplied with adequate irrigation in the year after low SWP, asparagus growth improves and does not appear to have a long term negative effect on plant performance.

Shoot Growth, Plant Tissue Elemental Composition, and Soil Salinity Following Irrigation of Alfalfa and Tall Fescue with High-Sulfate Waters

Abstract Groundwater contaminated with sulfate (SO4 2‐) at concentrations higher than allowable for drinking water might still be usable for irrigation. Objectives were to determine the growth response and mineral uptake of two forage crops irrigated with waters containing SO4 2‐ at concentrations ranging from 175 to 1743 mg/L, and with electrical conductivities (EC) ranging from 1.2 to 3.6 dS/m. Plants were grown for 12 weeks in 8‐L pots containing a calcareous sandy loam and were harvested at 4, 8, or 12 weeks for plant growth measurements and tissue analysis. Digested leaves, stems, and reproductive tissues were analyzed by inductively coupled plasma (ICP) spectroscopy at each harvest, as were saturated soil paste extracts. Shoot growth of tall fescue (Festuca arundinacea Schreb.) was not affected by irrigation water treatment, whereas shoot growth of alfalfa (Medicago sativa L.) was increased by a moderate level of soil solution SO4 2‐ Sulfur (S), boron (B), magnesium (Mg), sodium (Na), and zinc (Zn) ...

Monitoring root length density and root biomass in asparagus (Asparagus officinalis) with soil cores

Abstract Soil type, crop management practices, annual plant growth patterns, and seasonal changes in the soil environment all influence asparagus (Asparagus officinalis) roots. This study describes the dynamic changes in root growth that occur during the annual growth cycle of asparagus grown in two contrasting soil types and crop management systems. Root length density and biomass were estimated from soil cores (55 mm diam. × 0.2 m long) collected to 1 m in three locations adjacent to the row (0.15, 0.3, and 0.6 m from row centre). Samples were collected on six dates (early, or postharvest at early, mid, or late fern growth, and dormant period) between October 1999 and June 2000. Test sites varied with soil type (sandy loam or silt loam) and crop management system (normal 12‐week harvest or extended 15‐week harvest). Fleshy and fibrous roots were collected, root length density determined, and dry weights measured. Fleshy asparagus roots grew deeper in a sandy soil than in a silt soil, had higher dry matter content in silt than in sandy soil, and greater root length in a silt compared to a sandy soil. Fibrous root length density was greater during fern growth than during harvest, in a sandy versus a silt soil and at shallow versus deep sampling depths. Sampling date, soil depth, and sample location all significantly influenced asparagus fleshy and fibrous root biomass. Soil cores accurately estimated both total fleshy root length density and dry matter content when compared to the more time‐consuming complete root excavation. Results can be used to improve crop management practices, predict root biomass, and increase our understanding of the dynamics of root development in asparagus.

A Single Application of Phosphorus at Planting Improves Long-term Asparagus Root Growth and Yield

ABSTRACT Mature Asparagus (Asparagus officinalis L) plantings are only marginally responsive to added phosphorus (P). There is little information addressing P needs of new asparagus plantings. In 1999, a trial was established in a P-deficient soil to assess effects of increasing P levels at planting on asparagus growth and productivity. Prior to planting, 0 to 450 kg·ha−1 of P was blended in the planting furrow. Fleshy root growth and carbohydrate content were measured periodically and fern growth was evaluated during the summer and autumn of each year. Spears were harvested beginning in 2001. Increasing soil P levels had a variable effect on asparagus spear yield during limited harvests of 2001 and 2002. By full harvest in 2003–2005, spear yield increased linearly with increasing P. Yield increase was associated with a linear increase in root biomass but not root carbohydrate content. A single early application of P can improve asparagus productivity.