Paul V. Nelson

A humic acid improves growth of tomato seedling in solution culture

Abstract The effects of humic acid (HA) on nutrient accumulation and growth of tomato seedlings were evaluated in a solution of limited nutrient availability in a greenhouse. HA additions were made to the nutrient solution at rates of 0, 640, 1280, or 2560 mg/L. The addition of 1280 mg/L HA produced significant increases in shoot accumulation of P, K, Ca, Mg, Fe, Mn, and Zn as well as increased accumulation of N, Ca, Fe, Zn, and Cu in roots. Fresh and dry weights of roots were also increased, However, on comparing nutrient accumulation in plants treated with 1280 mg/L HA and those given an additional supply of nutrients equivalent to those supplied by HA at the 1280 mg/L rate, shoots accumulated more N, P, K, Fe, and Cu, while roots accumulated more K and Ca. Therefore these increases do not appear to be associated with nutrients contained in HA. Eectrolyte leakage, as an indication of membrane permeability, did not differ as a consequence of HA additions. However, electrolyte leakage correlated positivel...

Leaching of applied phosphorus in container media

Abstract Pre-plant P as superphosphate (8.7% P) at the rate of 1.5 kg m −3 was added to two root media in 16.5-cm azalea-type pots. Saturated media were periodically leached to 15% excess. Media type had a definite influence on P leached. Over one third of the total applied P was leached from a peat moss:vermiculite (PV) (1:1, v:v) mix after 9 weeks compared to less than 5% leached from a sand:soil:peat moss (SSP) (1:1:1, v:v:v) mix in a simulated plant watering scheme. Approximately the same amount of P was leached at any given watering in the PV (4.2%), whereas 2.6% of that applied was lost after an initial watering at 1 h and only 0.04% after an initial watering at 9 weeks in the SSP mix. This difference was related to differences in P fixation by the various root media components. P adsorption isotherms were conducted on 7 root media components or mixtures of components, including the 2 above-mentioned mixes, to determine the quantity of P adsorbed to give 0.2 ppm in the soil solution. The resulting plot of P adsorbed versus P in solution confirmed that the greater leaching loss of P in the soil-less mix was due to a lower P adsorption capacity. Maximum P adsorption capacity in the soilless media was reached with the addition of 262 g P m −3 . The adsorption capacities of soil, sand and SSP were not reached at the highest rate of P addition (524 g P m −3 . The higher P buffering capacity of these materials necessitates greater P addition to achieve 0.2 ppm soluble P, considered optimum for most plants, but ensures that the level of soluble P will be maintained for a longer period.

Effects of calcium source and temperature regime on calcium deficiency during hydroponic forcing of tulip

Abstract Tulips (Tulipa gesneriana L.) forced hydroponically in distilled water developed Ca deficiency symptoms, including topple and flower bud abortion. Prevention of Ca deficiency and uptake of Ca was greater when Ca was supplied in the NO3− form rather than as Cl− or SO42−. Calcium EDTA was injurious to plants at a concentration of 2.5 mM, a level too low to correct Ca deficiency. Addition of BO33−, K+, H2PO4−, or Hoaglands all nitrate solution with modified micronutrient levels to the Ca substrate failed to improve growth. The complete nutrient formulation reduced Ca uptake. Ca deficiency could not be prevented at the high temperature regime (22°C day–18°C night), due in part to suppress uptake of Ca. In the low temperature regime (18°C day–14°C night), a 5-mM solution of Ca(NO3)2 prevented Ca deficiency during all forcing periods. Similar results were obtained with a 7.5 mM solution of CaCl2.

The interaction of relative air humidity and carbon dioxide enrichment in the growth of Chrysanthemum × morifolium Ramat☆

Abstract Plants of Chrysanthemum × morifolium cultivar ‘Fiesta’ were grown hydroponically for 6 weeks in growth chambers at relative humidity (RH) levels of 50 and 95% and CO 2 levels of 340 and 940 μl l −1 in a Latin square combination. High RH as well as high CO 2 resulted in increased relative growth rate (RGR), increased dry weight of leaves, stems and roots, and increased leaf area on main and lateral stems during the first 2 weeks of growth. During this period, high CO 2 levels interacted to stimulate the RH effects. During the third to sixth weeks of growth, the interaction of RH and CO 2 was either lost or, as in the case of RGR and root dry weight, reversed in such a way that a negative effect of high CO 2 at high RG was found. At 6 weeks there were positive main effects of RH and CO 2 , but no interaction on plant height, number of leaves on lateral shoots, number of lateral shoots, and length of lateral shoots. The shoot to root dry weight ratio increased at high RH. Water consumption of plants decreased sharply at high RH and moderately at the high CO 2 level. Stomatal aperture was larger at high RH, but smaller at the high CO 2 level. It is concluded that increased plant growth resulting from increased RH might be caused by an increase in stomatal aperture which in turn facilitates CO 2 absorption and utilization.

Comparison of phosphate adsorption on clay minerals for soilless root media

Abstract The greenhouse industry aims to decrease phosphate discharge to help reduce eutrophication of surface waters, to reduce fertilizer consumption, and to maintain a more constant level of plant‐available phosphate. Iron and aluminum oxides and some aluminosilicate minerals are efficient sorbents for phosphate. The phosphate adsorption characteristics of synthetic hematite (α‐Fe2O3), goethite (α‐FeOOH), and allophane (Si3Al4O12 nH2O), and a commercial alumina (A12O3) were evaluated to determine their potential for reducing phosphate leaching from soilless root media. The pH dependence of phosphate adsorption and maximum adsorption capacities were determined by reacting each mineral with various levels of phosphate between pH 4.0 and 9.0 in a 10 mM potassium chloride (KCl) background solution. Adsorbed phosphate was determined by loss from solution. Adsorption envelopes (adsorbed phosphate versus pH) showed a decrease in phosphate adsorption with increasing pH, particularly for alumina and allophane, ...

Mineral nutrient concentration and uptake by tomato irrigated with recirculating aquaculture water as influenced by quantity of fish waste products supplied

Abstract Fish and tomato (Lycopersicon esculentum Mill.) production were linked in a recirculaing water system. Fish (tilapia) were fed a commercial diet with 32% protein. Tomato cultivars ‘Laura’ and ‘Kewalo’ were grown during summer 1988 and spring 1989, respectively, in a Raleigh, NC greenhouse. Plants were grown in biofilters at 4 plants/m2 and surface irrigated 8 times daily with water pumped from an associated fish tank. Four tank‐to‐biofllter ratios were established by varying the filter size. Each system received identical nutrient inputs and an equal quantity of water was applied per plant. Biofilter drainage returned to the tanks. Biological filtration, aeration, and mineral assimilation by plants maintained water quality within limits for tilapia. All nutrients were assimilated above deficiency levels. Tissue concentrations of N, P, K and Mg were not limiting. Calcium was low and S high when their sole nutrient source was fish waste. Micronutrients were assimilated in excess of sufficiency, but...

Pot soil air composition in conditions of high soil moisture and its influence on chrysanthemum growth

Abstract Chrysanthemums were grown in 15.2 cm standard pots in a heavy mix of clay loam soil+sphagnum peat moss (2:1). A fine texture mix was used to accentuate undesirable gas profiles in the soil. Soil air was analyzed at five depths in the soil profile. In one set of tests, water was applied to the top of the pot at a matrix potential in the center of the soil profile of −5 kPa. The average gas concentrations in soil air in the top and bottom fifths of soil were for O 2 —20.0 and 14.5%, for CO 2 —0.8 and 2.4%, and for C 2 H 4 —0 and 0.08 μ l dm −3 . Smooth concentration gradients of each gas occurred from top to bottom of the soil profile. The composition of soil air changed greatly during the drying cycle. At soil moisture tensions of −0.7, −2.5, and −5 kPa in the center of the soil profile, the gas concentrations in the lowest fifth of soil were for O 2 —9.6, 15.3, and 20.3%, and for CO 2 —4.5, 3.5, and 0.6%, respectively. Thus, soil atmospheric conditions for plant growth were poorest immediately after watering and continuously improved up to the time of watering. When pots of chrysanthemum were watered by capillary action from mats, the average concentration of gases in soil air in the lowest fifth of soil were 5.8% O 2 , 3.6% CO 2 , and 0.38 μ l dm −3 C 2 H 4 . This gas profile was less desirable for growth than the profile found in top-watered pots. Unlike the situation in top-watered pots, the gas concentrations in mat-watered pots were stable. Roots in top-watered pots were restricted to the upper two thirds of the soil ball, and were distributed evenly in the inner part of the soil and at the periphery. Roots of mat-watered plants developed further down the vertical periphery of the pot than roots of top-watered plants, but they did not grow inside the ball. Chrysanthemum plants were grown through a hole in the side wall of each of five 3.9 cm tall by 15.2 cm diameter plastic rings stacked vertically and separated by stainless steel screens that allowed for passage of water but not roots. Water was applied to the top of these cylinder stacks. The largest plants developed in the top ring with progressively smaller plants at lower depths. Plants in the lower two rings developed interveinal chlorosis and did not reach commercial size.

Ammonium toxicity in chrysanthemum: Critical level and symptoms

Abstract Three experiments were conducted to determine the critical meq NH4/meq K ratio in fresh tissue indicative of ammonium toxicity and the symptoms of the same under winter and summer conditions. Three and four levels each of ammonical N and K fertilization were employed in factorial designs. The chrysanthemum cultivars Bright Golden Anne and Yellow Mandalay were studied. Results indicate there was a critical range of NH4/K ratios from .025 to .026 below which NH4 injury never occurred and above which injury always occurred. The occurrence of injury within the range was erratic. Confidence limits for the critical range, based on one standard deviation as determined in Experiment 3, extend from .022 to .029. This range was applicable from the second to ninth week of plant growth and for winter crops as well as the summer crop. Symptoms of toxicity include reduction in growth rate, the development of small necrotic spots beginning on middle to lower leaves and progressing up the plant, thickened‐leathe...

Reaction Times of Twenty Limestones

Abstract Particle size and calcium carbonate equivalent characterize agricultural limestone. When agricultural limestone is used for horticultural container substrates, variations in pH among batches of substrate produced with the same limestone rate, as well as pH drift from initial pH, occur. Horticultural endeavors require more detailed characterization of limestone neutralization capacity than is provided for agricultural limestones. Reactivity of twenty limestones encompassing a broad range of calcium and magnesium carbonate were compared. Limestones were wet‐sieved into three particle‐diameter fractions and reacted with ammonium chloride in the presence of steam. Fine particles reacted faster than coarse; however, there was a point beyond which degree of fineness of calcitic limestone no longer affected reactivity. Dolomitic limestones were slower reacting than calcitic. Reactivity within particle fractions of dolomitic and coarse calcitic limestones varied significantly. These results indicate that particle diameter and calcium carbonate equivalent are not the only factors influencing limestone neutralization capacity.

EFFICACY OF SOYBEAN-BASE LIQUID FERTILIZER FOR GREENHOUSE CROPS

A soybean-base liquid fertilizer [Daniels Plant Food, Sherman TX, USA; 10 nitrogen (N):1.8 phophorus (P):2.5 potassium (K)] for petunia was compared for efficacy to two formulations of 20N:4.4P:16.6K with 40 and 70% of the nitrogen in the reduced form. Petunias treated with the soybean-base fertilizer were taller, flowered in 4.5% less time, had the highest plant rating for foliar color and plant form, and did not differ in plant dry weight from the control (40% reduced nitrogen). Foliar nitrogen concentration was not affected by fertilizer source. Also, cyclamen grown with the soybean-base fertilizer had similar plant and corm growth and formed 47% more flowers than the control. Foliar levels of potassium although lower were adequate in the soybean-base fertilized plants. Ammonium toxicity and potassium deficiency symptoms did not occur with either species. While the substrate pH in the high reduced nitrogen soybean-base treatment was expected to be lower, it was higher or similar to the control in each species.