Effect of extractable zinc,phosphorus, and soil ph on zinc concentrations in leaves of field‐grown corn

Abstract

The variability in corn yield responses to applications of Zn fertilizer appears to be associated with several complex soil and climatic factors that affect the availability of endogenous soil Zn to the crop under specific conditions. Among the soil chemical properties that influence availability of endogenous Zn are soil pH, organic matter content, and extractable P. Over a period of several years, soil and plant analysis data were collected from 54 field experiments, field trials, and diagnostic visits to producer's fields. These data were subjected to multiple regression analysis, resulting in an equation: Zn_leaf = 37.14 + 1.513 Zn_st ‐4.04 pH_st ‐ 1.791 ln(P_st/100) where Zn_st, pH_st, and P_st were 0.1N HC1 extractable soil Zn (kg/ha), 1:1 soil‐water pH, and Bray's 1 extractable soil P (kg/ha), respectively. These factors accounted for 67% of variation in leaf Zn, which was a large portion of the variability in Zn_leaf considering that climatic conditions, management levels, and varietal differences were uncontrolled in most instances. Using the previously published critical level in the leaf opposite and below the ear as 17 μg Zn/g, these data can be used to set required soil test levels of Zn at different levels of extractable P and soil pH. Inadequate levels of extractable Zn would range from 2.5 (at pH 6.0, P = 70 kg/ha) to, 9.5 kg/ha (at pH 7.5, P = 420 kg/ha).     

Response of burley tobacco to banded fertilizer and in‐row subsoiling

Abstract

Field experiments were conducted during 4 years at two locations in Kentucky to study the response of burley tobacco to phosphorus (P) and potassium (K) fertilizer rate and placement, and to in‐row subsoiling. In one experiment on Pope soil (mesic Fluventic Dystrochrepts), dry matter and P and K uptake 40 days after transplanting, and cured leaf yield and value/ha were increased as application of a 5–13–36 (%N‐P₂O₅‐K₂O) grade fertilizer increased from 310 to 930 kg/ha. Generally, fertilizer placed in 40‐cm wide bands directly under and parallel to the row was more effective than broadcasting and in‐row subsoiling was more effective than not subsoiling. Significant 2‐way and 3‐way interactions suggested that plant responses to band applications over broadcasting were greater in the presence than absence of subsoiling. In another experiment conducted on two silt loam soils, Pope and Maury (typic Paleudalfs), fertilizer applied in a 40‐cm band with in‐row subsoiling was more effective than broadcasting without subsoiling or placement in 10‐cm wide bands applied 0.6‐m apart and perpendicular to the row without subsoiling. Growth and yields increased up to the 620 kg/ha rate and 40 days after transplanting, soil pH decreased and soil electrical conductivity and plant manganese (Mn) increased with increased rate of fertilizer.     

Adsorption‐desorption of zinc in mollisols and their relationship with uptake of fertilizer‐applied zinc by rice

Abstract

Zinc (Zn) adsorption in mollisols conformed to the linear form of Freundlich equation. The log K values were positively correlated with silt, clay, and carbonate contents and soil pH, but negatively correlated with sand content. Sequential desorption of adsorbed Zn in 0.05M Ca(NO₃)₂, 0.1M Mg(NO₃)₂, 0.005M DTPA, and 0.1M HCl revealed that weakly and specifically bound fractions of added Zn, which could easily equilibrate with soil solution, were low and decreased with silt and carbonate contents and soil pH. Weakly bound fraction increased with sand content. Strongly bound and complexed fraction of applied Zn was the maximum and increased with clay, soil organic carbon and carbonate contents and specific surface area, but decreased with sand content. The mineral bound fraction of applied Zn was intermediate and increased with silt, clay and carbonate contents, and soil pH and specific surface area. Zinc uptake due to added Zn fertilizer by rice crop (Y) negatively correlated with log K, but positively related to Zn content in the equilibrium soil extract and Zn desorbed in 0.05M Ca(NO₃)₂. Both log K and l/n values together explained 59.5% of the total variation in Y, while Zn content in the equilibrium soil extract, Zn desorbed in 0.05M Ca(NO₃)₂, 0.005M DTPA and 0.1M HCl collectively accounted 79.6% of the total variation in Y.     

Availability of cobalt‐60 to corn and bean seedlings as influenced by soil type,lime, and DTPA

Abstract

Uptake of Co by corn (Zea mays) and bush beans (Phaseolus vulgaris) seedlings was affected by plant species, soil type and soil amendment. Bean leaves preferentially accumulated ⁶⁰Co in comparison with corn leaves. Both the DTPA and (lime and DTPA) treatments enhanced ⁶⁰Co uptake by both plant species, notably in the Troup soil which had lower cation exchange capacity (CEC) and lower soil fertility in comparison with Dothan soil. Conversely, soils with lime but without the chelating agent suppressed ⁶⁰Co uptake. This dictates that farming practices should be closely evaluated if crops for livestock and human consumption are to be raised in fields contaminated by radionuclides.     

Topsoil and subsoil potassium as affected by long‐term potassium fertilization of corn‐soybean rotations

Abstract

Long‐term potassium (K) fertilization practices are likely to affect the K content of soils. This study assessed the effect of long‐term K fertilization strategies for corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] rotations on extractable K in the soil profile of a major Iowa soil type at two locations. The soil type was a Webster fine‐loamy, mixed, mesic, Typic Haplaquoll at both sites. Soil samples were collected from the 0–15, 15–30, 30–60, and 60–90 cm depths after 17 years (Site 1) or 19 years (Site 2) of K fertilization with combinations of two initial rates and four annual rates. The initial rates were 0 and 1,344 or 1,120 kg K ha^‐1 at Site 1 and 2, respectively, and the annual rates ranged from 0 to 100 kg K ha^‐1. Samples were analyzed for ammonium acetate‐extractable K (STK) and nitric acid (HNO₃)‐extractable nonexchangeable K (HNO₃‐K). Concentrations of STK and HNO₃‐K in the top 0–15 cm soil layer at the two sites were higher for the high initial K rates and were linearly related with the annual K rate. Results for the subsoil layers varied between sites and extractants. At Site 1, annual rates of 30 kg K ha^‐1 or higher resulted in a relative accumulation of HNO₃‐K in the 15–30 cm layer. At Site 2, these rates resulted in relative accumulations of STK in the 30–60 cm layer and of HNO₃‐K in the 60–90 cm layer, but with relative depletions of STK in the 15–30 and 60–90 cm layers. Thus, use of one extractant may not always be sufficient to evaluate cropping and fertilization effects on subsoil K. Long‐term K fertilization of corn and soybean rotations affected extractable K of both the topsoil and subsoil. The effects on subsoil K, however, were smaller compared with effects on the topsoil and varied markedly between sites, subsoil layers, and extractants.     

Effects of zinc fertilization and irrigation on grain yield and zinc concentration of various cereals grown in zinc‐deficient calcareous soils

Effects of varied irrigation and zinc (Zn) fertilization (0, 7, 14, 21 kg Zn ha^‐1 as ZnSO₄7.H₂O) on grain yield and concentration and content of Zn were studied in two bread wheat (Triticum aestivum), two durum wheat (Triticum durum), two barley (Hordeum vulgare), two triticale (xTriticosecale Wittmark), one rye (Secale cereale), and one oat (Avena sativa) cultivars grown in a Zn‐deficient soil (DTPA‐extractable Zn: 0.09 mg kg^‐1) under rainfed and irrigated field conditions. Only minor or no yield reduction occurred in rye as a result of Zn deficiency. The highest reduction in plant growth and grain yield due to Zn deficiency was observed in durum wheats, followed by oat, barley, bread wheat and triticale. These decreases in yield due to Zn deficiency became more pronounced under rainfed conditions. Although highly significant differences in grain yield were found between treatments with and without Zn, no significant difference was obtained between the Zn doses applied (7–21 kg ha^‐1), indicating that 7 kg Zn ha^‐1 would be sufficient to overcome Zn deficiency. Increasing doses of Zn application resulted in significant increases in concentration and content of Zn in shoot and grain. The sensitivity of various cereals to Zn deficiency was different and closely related to Zn content in the shoot but not to Zn amount per unit dry weight. Irrigation was effective in increasing both shoot Zn content and Zn efficiency of cultivars. The results demonstrate the existence of a large genotypic variation in Zn efficiency among and within cereals and suggest that plants become more sensitive to Zn deficiency under rainfed than irrigated conditions.     

Response of pineapple to mycorrhizal inoculation and fosetyl‐Al treatment

Abstract

A pot experiment was conducted in the greenhouse to determine the influence of vesicular‐arbuscular mycorrhizal (VAM) inoculation on growth of pineapple (Ananas comosus, cv.’Smooth Cayenne') and its interaction with fosetyl‐Al in a Wahiawa soil (Tropeptic Eutrustox) at soil solution P levels of 0.003, 0.02 and 0.2 mg/L. Pineapple crowns were dipped in a solution of fosetyl‐Al before planting. Inoculation of soil with the fungus Glomus aggregatum (Schenck & Smith emend. Koske) significantly increased VAM colonization of pineapple roots at soil solution P levels of 0.003 and 0.02 mg/L. VAM inoculation also increased mycorrhizal effectiveness measured six weeks after planting. At harvest, pineapple grown in the inoculated soil at the lowest P level had significantly higher D‐leaf P concentration and plant fresh weight than that grown in the uninoculated soil. Fosetyl‐Al appears to have no significant effect on VAM‐pineapple interaction.     

Effect of seed zinc content on grain yield and zinc concentration of wheat grown in zinc‐deficient calcareous soils

Field experiments were carried out to study the effect of different seed‐zinc (Zn) content on grain yield and grain Zn concentration in a bread wheat cultivar Atay 85 grown in a severely Zn‐deficient soil under rainfed and irrigated conditions for two years. Three groups of seeds with Zn contents of 355, 800, and 1,465 ng Zn seed^‐1 were obtained through different number of foliar applications of ZnSO₄.7H₂O in the previous crop year. Experiments were carried out with 23 kg Zn ha^‐1 (as ZnSO₄.7H₂O) and without Zn fertilization to the soil. Grain yield from seeds with 800 and 1,465 ng Zn seed^‐1 content was significantly higher than that from low seed‐Zn, especially under rainfed conditions. In the first year, under rainfed and Zn‐deficient conditions, yield of plants grown from the highest seed‐Zn content was 116% higher than the yield of plants grown from the low seed‐Zn content. However, in the first year soil‐Zn application combined with low‐Zn seed resulted in a yield increase of 466% compared to nill Zn treatment with low‐Zn seed, indicating that higher seed‐Zn contents could not compensate for the effects of soil Zn application. Soil Zn application significantly increased Zn concentrations in shoot and grain. However, the effect of different seed Zn contents on Zn concentrations of plants was not significant, probably due to the dilution of Zn in tissues resulting from enhanced dry matter production. The results presented show that wheat plants grown from seed with high Zn content can achieve higher grain yields than those grown from the low‐Zn seed when Zn was not applied to the soil. Therefore, sowing seeds with higher Zn contents can be considered a practical solution to alleviate Zn deficiency problem, especially under rainfed conditions in spite of it being insufficient to completely overcome the problem.     

Response of summer‐planted potatoes to level of applied nitrogen and water

The irrigation and nitrogen (N) requirements of potatoes (cv. Delaware) were determined using sprinklers in a line‐source design on a Spearwood sand. Irrigation water was applied at 73 to 244% of the daily pan evaporation (Epan) and N at 0 to 800 kg N ha^‐1 (total applied) as NH₄NO₃ in 10 applications post‐planting. There was a significant yield (total and marketable) response to irrigation, at all levels of applied N, and N at all levels of applied water (P<0.001). The interaction between irrigation and N was also significant (P<0.001). There was no significant yield response to irrigation from 149% Epan (i.e., W3 treatment) to 244% Epan (i.e., W6 treatment). Irrigation at 125 and 150% of Epan was required for 95 and 99% of maximum yield, respectively, as determined from fitted Mitscherlich relationships. Critical levels of N required for 95 (417 kg ha^‐1) and 99% (703 kg ha^‐1) of maximum yield were also determined from a Mitschlerlich relationship fitted to the average of the W3 to W6 treatments. The percent total N and nitrate‐N in petioles of youngest fully expanded leaves required for 95 and 99% of maximum yield was 1.78 and 2.11, respectively, at the 10 mm tuber stage, and 0.25 and 0.80% at the 10mm plus 14 day stage (from quadratic regressions). There was a significant (P≤0.001) increase in N uptake by tubers with level of applied N from 57 kg ha^‐1 at 0 kg applied N ha^‐1 to 190 kg ha^‐1 at 800 kg applied N ha^‐1 (from a Mitscherlich relationship fitted to the average of W3 to W6 treatments). After accounting for N uptake from soil reserves (57 kg N ha^‐1), apparent recovery efficiency (RE) of fertilizer N by tubers [RE=(Up‐Uo/Np) where Up=uptake of N by the crop, Uo=uptake in absence of applied N and Np is the level of applied N, expressed as a fraction] declined from 0.28 at 100 kg applied N ha^‐1 to 0.17 at 800 kg applied N ha^‐1. There was a linear increase in ‘after cooking darkening’ (i.e., greying) of tubers with increasing level of applied N. Conversely, ‘sloughing’ (i.e., disintegration) of tubers decreased (inverse polynomial) with increasing level of applied N. Rate of irrigation had no effect on these cooking qualities. Reducing applied irrigation and N from levels required for 99% of maximum yield to levels required for 95% of maximum yield would not lead to a significant reduction in profit. This would increase apparent recovery efficiency of applied N by plants, maintain tuber quality, and reduce the impact of potato production on the water systems of the Swan coastal plain.     

Response of soybean to foliar‐applied boron and magnesium and soil‐applied boron 1

Annual plants may partition carbon (C) preferentially to reproductive structures slowing root elongation and subsequent nutrient uptake. Although foliar applications of nitrogen (N), phosphorus (P), potassium (K), and sulfur (S) supplement uptake by roots, soybean [Glycine max (L.) Merr.] yield increases have not been found in most studies. Experiments were designed to determine if foliar applications of boron (B), magnesium (Mg), or B+Mg would increase soybean yield and if soybean would respond to B applied to the soil several weeks prior to planting. Foliar B or Mg applied separately four times during reproductive growth did not affect soybean yield. However, four foliar applications of B+Mg increased soybean yield 12% at Mt. Vernon and 4% at Columbia over a three‐year period. Two foliar applications of B+Mg during the late reproductive stages increased soybean yield 8% over a two‐year period. The yield increase from foliar B+Mg treatment resulted from an increased number of pods on the main stem (18%) and branches (44%). A 2.8 kg/ha B application to soil eight weeks prior to planting increased soybean yield 11% during the first year and 13% the second year but had no effect on soybean yield by the third year after application. When results from the first two years were combined, 2.8 kg/ha B applied to soil increased the number of pods per branch by 17% and the number of branch pods per plant by 39%. Foliar applications of B+Mg increased soybean yield in four of six site‐years in the three‐year experiments at two locations.     

Response to iron‐deficiency stress of pear and quince genotypes 1

Roots of iron (Fe)‐efficient dicots react to Fe‐deficiency stress by strongly enhancing the ferric (Fe³⁺)‐reductase system and by lowering the rhizo‐sphere pH. In this study, we tested whether such adaptation mechanisms characterize pear and quince genotypes known to have differential tolerance to calcareous and alkaline soils. Two trials were performed using micropagated plants of three quince rootstocks (BA29, CTS212, and MC), three Pyrus communis rootstocks (OHxF51 and two selections obtained at the Bologna University: A28 and B21) and of two pear cultivars (Abbé Fétel and Bartlett, own‐rooted). In the first trial, plants were grown in a nutrient solution with [Fe(+)] and without [Fe(‐)] Fe for 50 days. Their root Fe‐reducing capacity was determined colorimetrically using ferrozine and FeEDTA, and Fe uptake of Fe(+) plants was estimated. In the second trial, the rhizosphere pH of plants grown in an alkaline soil was measured by a micro‐electrode. With the only exception of pears OHxF51 and A28, whose Fe‐reduction rates were similar in Fe(+) and Fe(‐) plants, the Fe‐deficiency stress resulted in a significant decrease in Fe reduction. Among the Fe(‐) plants, the two pear cultivars, OHxF51 and A28, had a higher Fe‐reducing capacity than the quince rootstocks and the cv. Abb6 F. When plants were pre‐treated with Fe, reduction rate was highest in the P. communis rootstocks, intermediate in the own‐rooted cultivars, and lowest in the quinces. Root Fe‐reducing capacity of Fe(+) plants proved to be linearly and positively correlated with Fe uptake and root proton release. Rhizosphere pH was highest in quince MC, intermediate in the other two quinces and in the cv. Abbe F., and lowest in the pear rootstocks and in the cv. Bartlett. Our results indicate that roots of pear and quinces do not increase their ability to reduce the Fe under Fe‐deficiency stress. The genotypical differential tolerance to Fe chlorosis likely reflects differences in the standard reductase system and in the capacity of lowering the pH at the soil/root interface. The determination of the root Fe‐reducing capacity is a promising screening technique for selecting pear root‐stocks efficient in taking up Fe.     

Response of Chickpea Cultivars to Application of Boron in Boron‐Deficient Calcareous Soils

Abstract

This study was conducted to investigate the effects of four boron (B) doses (control, 0 kg B ha^?1; B₁, 1 kg B ha^?1; B₂, 3 kg B ha^?1; and B₃, 6 kg B ha^?1) in soils deficient in available B (0.19 mg B kg^?1) and lime (CaCO₃) content (20.7%) on yield and some yield components of five chickpea (Cicer arietinum L.) genotypes, namely Akçin‐91, Population, Gökçe, ?zmir‐92, and Menemen‐92 in central Anatolian Turkey in the 2002 and 2003 growing seasons. Plant height, pods per plant, grain yield, protein content, protein yield, thousand seed weight, and leaf B concentration were measured. Grain yields in all genotypes (except for Gökçe) were significantly increased by 1 kg ha^?1 B application. Application of 1 kg ha^?1 B increased the yield by an average of 5%. Genotypes studied showed significant variations with respect to their responses to additional B. Akçin‐91 gave the highest grain yield (1704.8 kg ha^?1) at 3 kg B ha^?1, whereas Population, ?zmir‐92, and Menemen‐92 yielded best (1468.2 kg ha^?1, 1483.0 kg ha^?1, and 1484.7 kg ha^?1, respectively) at 1 kg B ha^?1. Interestingly, Gökçe reached to the highest level of grain yield (1827.1 kg ha^?1) at the control. Gökçe was a B deficiency B tolerance genotype. The other genotypes appeared to have high sensitivity to B deficiency. This study showed that B deficiency could result in significant yield losses in chickpea under the experimental conditions tested. Thus, B contents of soils for the cultivation of chickpea should be analyzed in advance to avoid yield losses.     

Differences in shoot growth and zinc concentration of 164 bread wheat genotypes in a zinc‐deficient calcareous soil

Abstract

A greenhouse experiment was carried out to study severity of the zinc (Zn) deficiency symptoms on leaves, shoot dry weight and shoot content and concentration of Zn in 164 winter type bread wheat genotypes (Triticunt aestivum L.) grown in a Zn‐deficient calcareous soil with (+Zn=10 mg Zn kg^?1 soil) and without (‐Zn) Zn supply for 45 days. Tolerance of the genotypes to Zn deficiency was ranked based on the relative shoot growth (Zn efficiency ratio), calculated as the ratio of the shoot dry weight produced under Zn deficiency to that produced under adequate Zn supply. There was a substantial difference in genotypic tolerance to Zn deficiency. Among the 164 genotypes, 108 genotypes had severe visible symptoms of Zn deficiency (whitish‐brown necrotic patches) on leaves, while in 25 genotypes Zn deficiency symptoms were slight or absent, and the remaining genotypes (e.g., 31 genotypes) showed mild deficiency symptoms. Generally, the genotypes with higher tolerance to Zn deficiency originated from Balkan countries and Turkey, while genotypes originating from the breeding programs in the Great Plains of the United States were mostly sensitive to Zn deficiency. Among the 164 wheat genotypes, Zn efficiency ratio varied from 0.33 to 0.77. The differences in tolerance to Zn deficiency were totally independent of shoot Zn concentrations, but showed a close relationship to the total amount (content) of Zn per shoot. The absolute shoot growth of the genotypes under Zn deficiency corresponded very well with the differences in tolerance to Zn deficiency. Under adequate Zn supply, the 10 most Zn‐ inefficient genotypes and the 10 most Zn‐efficient genotypes were very similar in their shoot dry weight. However, under Zn deficiency, shoot dry weight of the Zn‐efficient genotypes was, on average, 1.6‐fold higher compared to the Zn‐inefficient genotypes. The results of this study show large, exploitable genotypic variation for tolerance to Zn deficiency in bread wheat. Based on this data, total amount of Zn per shoot, absolute shoot growth under Zn deficiency, and relative shoot growth can be used as reliable plant parameters for assessing genotypic variation in tolerance to Zn deficiency in bread wheat.     

Response of Corn Growth in Salt‐Affected Soils of Northeast China to Flue‐Gas Desulfurization By‐product

Abstract

In semiarid and arid regions, plant growth is limited by high pH, salinity, and poor physical properties of salt‐affected soils. A field experiment was conducted in the semiarid region of Kangping in northeast China (42°70′ N, 123°50′ E) to evaluate a soil‐management system that utilized a by‐product of flue‐gas desulfurization (FGD). Soil was treated with 23,100 kg ha^?1 of the by‐product. Results of corn growth were grouped into three grades (GD) according to stages of corn growth: GD1, seeds did not germinate; GD2, seeds germinated but corn was not harvested; and GD3, plants grew well and corn was harvested. The pH, electrical conductivity (EC), bicarbonate (HCO₃ ^?), carbonate (CO₃ ^2?), exchangeable and soluble calcium (Ca²⁺), chloride (Cl), and sulfate (SO₄ ^2?) in surface soils of the three grades (>20 cm) was measured to assess the correlation between corn growth and soil properties. Vertical differences in subsoil properties (0‐100 cm) between GD1 and GD3 were compared to known benchmark soil profiles. The FGD by‐product significantly increased EC, exchangeable and soluble Ca²⁺, and SO₄ ^2? and decreased CO₃ ^2?, exchangeable sodium (Na⁺), and soluble Na⁺. pH, EC, HCO₃ ^?, CO₃ ^2?, and Cl^? were higher in surface soils of GD1 than GD3. Soil hardness, soil moisture content, Cl^?, and calcium carbonate (CaCO₃) were higher in GD1 than in GD3, whereas the amount of available P was lower in GD1. Interestingly, the concentration of Cl^?, a toxic element for plant growth, was 2.5 and 1.5 times higher in GD1 than in GD3 and control soil, respectively. In the comparison study of subsoils, GD1 and GD3 were classified as having typical characteristics of saline‐alkali soil (pH>8.5; exchangeable‐sodium‐percentage [ESP]>15; EC>4.0) and alkali soil (pH>8.5; ESP>15; EC<4.0), respectively.     

Cadmium sulfate application to sludge‐amended soils: II. Extraction of Cd,Zn and Mn from solid phases

Abstract

Cadmium, Zn and Mn in eleven paired soils (one which had a history of sludge application and a control from adjacent land where sludge had not been used) were partitioned into five fractions: exchangeable, adsorbed, organically bound, carbonate bound and sulfide, by the use of KNO₃, H₂0, NaOH, EDTA and HNO₃, respect‐ively. The data indicate that the major portion of the total metals was found in the carbonate, sulfide and organic fractions. Addition of CaCO₃caused an increase in the exchangeable + soluble fractions of added Cd in the soils, but had little effect on native or sludge derived Cd.     

No‐tillage corn response to placement of fertilizer nitrogen,phosphorus, and potassium

Abstract

Fertilizer placement for corn (Zea mays L.) has been a major concern for no‐tillage production systems. This 3‐yr study (1994 to 1996) evaluated fertilizer phosphorus (P) or potassium (K) rates and placement for no‐tillage corn on farmers’ fields. There were two sites for each experiment involving fertilizer P or K. Treatments consisted ofthe following fertilizer rates: 0,19,and 39 kg P ha^‐1 or 0, 51, and 102 kg K ha^‐I. The fertilizer was broadcast or added as a subsurface band 5 cm beside and 5 cm below the seed at planting. Early plant growth, nutrient concentrations, and grain yields were measured. At the initiation of the study, soil test levels for P and K at the 0–1 5 cm depths ranged from optimum (medium) to very high across sites. Effects of added fertilizer and placement on early plant growth and nutrient concentrations were inconsistent. Added fertilizer had a significant effect on grain yields in two of twelve site‐years. Therefore, on no‐tillage soils with high fertility, nutrient addition, and placement affected early plant growth and nutrient utilization, but had limited effect on grain yield. Consequently, crop responses to the additions of single element P or K fertilizers under no‐tillage practices and high testing soils may not result in grain yield advantages for corn producers in the Northern cornbelt regardless of placement method.     

Response of no‐tillage and conventional‐tillage cotton to starter fertilization on loess soils

Starter fertilizers have been utilized to improve cotton (Gossypium hirsutum L.) yields, but yield increases have differed with soil type, application method, application rates, and tillage. Starter fertilizer tests were conducted from 1991 through 1993 on a Gigger silt loam (Typic Fragiudalf) in Louisiana and on a Loring silt loam soil (Typic Fragiudalf) in Tennessee to evaluate methods and application rates of 11–37–0 liquid fertilizer for cotton. Treatments were evaluated under conventional‐tillage (CT) and no‐tillage (NT) production systems. Application methods included in‐furrow application at planting (IF), spraying a 4‐inch wide surface band behind the planter (SB), and banding fertilizer two inches to the side and two inches below the seed at planting (2×2). The IF treatments were applied at 1.5, 3.0, and 4.5 gal/A. The SB and 2×2 treatments were applied at 7.5 gal/A. Starter fertilizer treatments were supplemented with broadcast granular fertilizers to achieve a total fertilization rate of 80–40–60 (N‐P₂O₅‐K₂O lb/acre). Starter fertilizer treatments were compared to broadcasting 80–40–60 and 80–0–60. Soil test levels for phosphorus (P) were high on both soil types. In‐furrow applications of 3.0 and 4.5 gal/acre usually reduced plant population for both tillage systems on both soil types. The 1.5 gal/acre IF treatment was less detrimental to stand establishment than the higher IF rates. The effect of starters on plant height varied from year to year. Starter fertilizers usually did not affect early‐season plant height relative to broadcast treatments. In several experiments starter fertilization increased plant height compared to one, but not both, of the broadcast fertilization treatments. High IF rates (3.0 and 4.5 gal/acre) reduced plant height in one experiment. The 2×2 starter fertilizer treatment increased leaf area per plant relative to the broadcast fertilization treatments in two of six experiments on the Gigger soil. Responses for NT and CT studies were similar. In one CT experiment on the Loring soil, the 1.5 gal/acre IF treatment increased leaf area relative to the broadcast treatments. Lint yield responses to starter fertilization were inconsistent. Starter fertilization increased lint yield in one of six experiments on the Gigger soil and in two of six experiments on the Loring soil. Increased yields from starters varied with year and application method, however, the 2×2 and SB treatments tended to provide better responses than IF treatments. Starter fertilizer responses for NT and CT tests were generally similar.     

Nitrogen for no‐tillage corn in Virginia: Sources and time of application

Abstract

No‐tillage corn (Zea mays L.) culture normally entails the placement of N fertilizer on the soil surface without mechanical incorporation. This field investigation was conducted to compare the N fertilizers that are most widely used in Virginia, when applied in this manner, for their effectiveness in producing notillage corn. Comparisons of the time of applying NH₄NO₃ were also made. Grain and stover yields, in addition to N removed in the crop, were used to draw conclusions. The experiments were conducted on both fertile and infertile soils in 1972 and 1973, both of which were relatively wet years. The fertilizers tested, urea, NH₄NO₃, and N solutions, were equally effective, per unit of N applied. Split applications of NH₄NO₃ showed no statistically significant advantage over all applied at planting but slightly trended to do so. N deficiency reduced grain yields relatively more than stover yields.     

Extractability of previously‐applied zinc as influenced by properties of calcareous soils

Abstract

The recovery of applied zinc (Zn) by plants is relatively small. Coupled with lack of leaching, this leads to accumulation of Zn in topsoil which may result in unfavorable growth conditions for the subsequent plants. Different extractants may be used for assessing the Zn status of soils previously treated with Zn sources. The extractability of retained Zn is influenced by soil properties. This experiment was conducted to study the influence of selected properties of calcareous soils on extractability of Zn by three popular Zn soil tests. Twenty samples from surface horizons (0–20 cm) of highly calcareous soils of southern Iran (pH 7.9 to 8.5; calcium carbonate equivalent 16 to 58%) previously treated with three levels of Zn (0, 10, and 20 mg Zn kg^‐1 soil as ZnSO₄#lb7H₂O) in triplicate and under one crop of corn (Zea mays L.) were extracted with DTPA, EDTA‐(NH₄)₂CO₃ and Na₂‐EDTA. Extractability (EXT) in a particular extractant was defined as the slope of the regression line, relating extractable Zn of each soil to the rate of applied Zn, multiplied by 100. The EXT values of soils ranged from 24.9 to 73.0% for DTPA, 47.2 to 84.4% for EDTA‐(NH₄)₂CO₃, and 28.2 to 56.7% for Na₂‐EDTA. Stepwise regression equations showed that cation exchange capacity (CEC) and calcium carbonate equivalent (CCE) followed by clay content were the most influential soil properties in EXT of retained Zn of highly calcareous soils. The EXT values decreased with increase in CEC, and CCE but increased with increase in clay.     

Response of four woody ornamental species to superphosphate and controlled‐release fertilizers

Abstract

Shoot dry weights of Ilex vomitoria Ait. ‘Schellings Dwarf’, Pittosporum tobira Thunb., and Juniperus chinensis L. ‘Blue Vase’ fertilized with Sref 20N‐2P‐8K and Step (micronutrient formulation) or Osmocote 18N‐3P‐10K and Micromax (micronutrient formulation) were not different when grown in a 1 sedge peat: 1 cypress sawdust: 1 cypress shavings (v/v/v) medium with or without superphosphate. Photinia X fraseri Dress shoot and root dry weights decreased if supersphosphate was added to the growing medium and fertilized with Sref and Step, but were not different when fertilized with Osmocote and Micromax. Shoot tissue P levels of P. X fraseri and P. tobira increased with the addition of superphosphate regardless if Osmocote and Micromax or Sref and Step were used, but there was no corresponding increase in shoot dry weight. Water soluble P levels of the superphosphate amended medium with Sref and Step decreased about 70 ppm during the 6‐month experimental period.