Significant Yield Response Research Articles

Determining wheat responses to copper in prairie soils

Criteria for assessment of the Cu status of prairie soils were developed in the early 1980s and are currently in use with some modifications. Although there appears to be a reasonable agreement on the soil critical value of 0.4 mg kg-1 soil based on DTPA-extractable Cu, a marginal range that extends between 0.4 and 1.2 mg DTPA-Cu kg-1 soil is used to generate fertilizer recommendations. The objective of this study was to verify the existing soil critical value and identify the frequency of agronomic as well as economic response of spring wheat to Cu fertilization on soils with levels both below and above the critical value. We carried out a large number (52) of trials with spring wheat (Triticum aestivum L.) between 1991 and 2000 in all three Prairie Provinces and compiled a large number of spring wheat experiments conducted in western Canada (63) by a number of researchers. Fifty-nine trials carried out on soils containing marginal and sufficient Cu levels were evaluated and were compared to 56 experiments on soils containing deficient levels. A number of methods of placement and products were compared. Agronomic responses were obtained in 41 of the 115 experiments and only by broadcasting either 3 to 5.5 kg Cu ha-1 as CuSO4·5H2O or 0.5 to 2 kg Cu ha-1 as Cu-sulphonate and incorporating the product or by foliar application of 0.22 kg Cu ha-1. Calibration of the DTPA-extractable Cu test using a Mitscherlich type of function verified the soil critical value of 0.4 mg Cu kg-1 soil. Statistically significant grain yield responses were obtained in 87, 16 and 0% of trials carried out on soils containing <0.4, 0.4 to 0.8 and >0.8 mg DTPA-extractable Cu kg-1 soil. Economic responses, defined as those where Cu application yielded a 2:1 return on the cost of fertilizer in the year of application, varied depending on the price of wheat and ranged between 19 to 45% in deficient soils for a price range of $100 to $200 t-1 of wheat grain; economic responses on marginal and sufficient soils occurred in 6% and none of the cases, respectively. Hence, fertilization of soils with DTPA-extractable Cu levels >0.4 mg kg-1 is associated with very high risk. Key words: DTPA-extractable, calibration, soil critical value, deficient, marginal, agronomic, economic

Application of seed-row potash to barley (Hordeum vulgare L.) grown on soils with high “available” potassium levels

Benefits of KCl application to cereals have been documented in Great Plains soils and have been attributed primarily to a response to the Cl- portion of this fertilizer either due to disease suppression or a Cl- deficiency. The practice of placing small amounts of KCl with the seed to avert any of these undesirable effects has been gaining momentum in western Canada. However, research on benefits from KCl fertilization of barley on high K soils in western Canada is limited. A large number of trials (115) were conducted from 1989 to 1998 on western Canadian prairie soils to ascertain the response of barley to seed-row applied KCl fertilizer. All soils contained K levels in excess of what is considered a critical level for obtaining a yield response to K due to K deficiency. Statistically significant yield increases with KCl application were obtained in 37 of 115 trials (32%). There appeared to be a strong link between the probability of obtaining a significant yield response to seed-row applied KCl, and barley cultivar and previous crop. Growing Harrington barley on barley stubble resulted in a grain yield increase due to KCl seed-placement 60% of the time. However, no clearly defined mechanism for the grain yield responses could be drawn based on the determined parameters, except that the majority of responses did occur under conditions that promote disease (e.g., disease susceptible cultivar, barley sown on barley stubble, etc.) and that the lower the soil “available” K levels in those instances, the higher the grain yield increase. Hence, it is hypothesized that K may play an indirect role in suppressing disease by increasing the overall health of plants. None of the assessed plant characteristics other than yield, i.e., days to maturity, kernel plumpness, protein and root rot infection, benefited from application of Cl- as either KCl or CaCl2. Key words: Chloride, cultivar, Harrington, disease, plant health, previous crop

Early planting and overseeding in the cultural control of rice seedling maggot Atherigona oryzae Malloch in the Philippines

Rice seedling maggot Atherigona oryzae Malloch is a minor pest of upland rice Oryza sativa L. and maize Zea mays L. in the Philippines. Two cultural control methods, early planting and overseeding, were evaluated separately on upland rice in an eroded, high rainfall area in Northern Mindanao. Farmers plant maize ahead of upland rice in separate fields with the onset of the rainy season. Regression analysis from data over six seasons showed on average the first 50% of farmers who planted ahead of their neighbours suffered damage significantly below the 5% deadheart action threshold. When early rice planting relative to one's neighbours was combined with earliness with regard to sowing maize, damage was further reduced. Useful methods for forecasting deadheart incidence 1-2 months ahead of rice planting were developed. The deadheart incidence rate was highly correlated with the amount of rain that fell in February and March as well as with the number of adults collected from bait traps in March or April. Six seeding rates were compared in 20-kg increments from 50 to 150 kg/ha with and without insecticide seed treatment. There was no significant yield response over the seeding rates tested when protected by insecticide, but when untreated, the highest yield occurred at 120 kg seed/ha and the greatest return at 90 kg/ha. Yields declined above the 120 kg/ha level from interplant competition. Rice seedling maggot egg density decreased but the deadheart incidence rate increased with increasing plant densities, both linearly. Perhaps higher plant densities led to greater larval survival and dispersal. Planting rice early is dependent on early maize planting. Planting maize early and following maize within the generation period of rice seedling maggot with rice sown from 90 to 120 kg/ha would be particularly beneficial in years when the rice seedling maggot is predicted to be a high risk.

Tissue testing to assess the sulfur requirements of subterranean clover on very sandy soils in high rainfall areas of south-western Australia

Tissue testing was studied in field experiments between 1979 and 1985 to predict when sulfur (S) fertiliser was required for pastures in high rainfall (>650 mm annual average) areas of south-western Australia. The pastures comprised about half subterranean clover and annual ryegrass (Lolium rigidum Gaud.), the major pasture species in the region. Tissue testing was done for each species, using: (i) whole shoots, the present method used by commercial laboratories in Western Australia; (ii) youngest open leaves (legumes, YOLs) or youngest expanded blades (grass, YEBs); (iii) old leaves and blades (leaves that were not YOLs or YEBs); and (iv) stems (left after removal of YOLs, YEBs, old leaves and blades). Dried tissue was measured for total S, sulfate S, the total nitrogen : total S ratio and the sulfate S : total S ratio. For each pasture species, tissue test values were related to yield of dried herbage of that species measured for plants cut at ground level. Fertiliser nitrogen was not applied in the experiments.Annual ryegrass showed no significant yield responses to applied fertiliser S for all harvests in all experiments. Subterranean clover showed significant yield responses for most harvests of all experiments. At each site in each year, yield responses to applied S tended to become larger as the growing season progressed. For subterranean clover critical S values related to 90% of the maximum (relative) yield varied for different harvests of the same experiment within and between years, and for different experiments in the same and different years. As determined from all data, critical S values were similar for all plant parts (whole shoots, YOLs, old tissue, stems), with no consistent, systematic trend with plant age, and were: total S, range 0.10–0.30% S, mean 0.23%; sulfate S, range 0.01–0.14%, mean 0.04%; total N : total S ratio, range 11–30, mean 19; sulfate S : total S ratio, range 0.01–0.48, mean 0.27. The exception was that total S was lower for clover stems, the range being 0.06–0.20%, and mean 0.13%. Therefore, % total S in clover shoots can continue to be used as an indicator of sulfur deficiency in subterranean clover in the region.

Response of annual pastures to applications of limestone in the high rainfall areas of south-western Australia

The yield response of long-term pastures growing on acidified soil to applications of limestone (0, 2.5, 5.0, 7.5 and 10.0 t/ha with adequate magnesium fertiliser, and 0 and 5 t/ha with no magnesium fertiliser) was measured in 5 field experiments on different representative soils of the high rainfall areas of south-western Australia. After application, limestone was incorporated 1 cm deep in 3 experiments, 3 cm deep in 1 experiment, and 7 cm in another experiment. The pastures comprised subterranean clover (Trifolium subterraneum), and annual and Italian ryegrass (Lolium rigidum and L. multiflorum), the dominant species found in intensively grazed dairy and beef pastures of the region. Yields were measured when ryegrass plants had 3 leaves per tiller, which is when pastures in the region are grazed to maximise utilisation by cattle.Subsoil acidity was a problem at 4 of the 5 sites, and was so severe at 1 site that, despite having the lowest soil pH to 50 cm depth, there was no yield response to limestone incorporated to 3 cm deep. Applications of fertiliser magnesium had no significant effect on pasture production, soil pH, aluminium and manganese, or concentration of magnesium in dried herbage in any of the 5 experiments. Increasing amounts of limestone consistently: (i) increased soil pH, by between 1–2 pH units in the top 5 cm of soil, and 0.5–1.0 of a pH unit in the 5–10 cm soil profile; and (ii) decreased, by up to 84–98%, the amount of exchangeable aluminium in the 0–5 and 5–10 cm soil profiles. During 3 years (1998–2000) there were: (i) no yield responses to limestone for a total of 9 assessments on a sand, or 11 assessments on a sandy gravel; (ii) 2 significant (P<0.05) yield responses to limestone, from a total of 8 assessments on a loamy clay and from 9 assessments on a loam; (iii) 9 significant yield responses from a total of 13 assessments on a sandy loam (2 from 5 assessments in 1998, 3 from 4 assessments in 1999, and all 4 assessments in 2000). The sandy loam had the largest amount of exchangeable aluminium in the top 5 cm of soil [about 1.6 cmol(+)/kg, accounting for 35% of the exchangeable cations]. Increasing limestone applications did not induce deficiency or toxicity of any nutrient elements in subterranean clover or ryegrass dried herbage and, for dried herbage of bulk samples of both species, had no effect on dry matter digestibility, metabolisable energy and concentration of crude protein.

SHORT DURATION CHICKPEA TO REPLACE FALLOW AFTER AMAN RICE: THE ROLE OF ON-FARM SEED PRIMING IN THE HIGH BARIND TRACT OF BANGLADESH

Chickpea (Cicer arietinum) is a promising post-wet-season crop to follow rainfed rice (Oryza sativa) in the High Barind Tract of northwestern Bangladesh. Yields in farmers' fields, however, remain low (<1 t ha−1) primarily due to such factors as poor crop establishment, late sowing, and terminal drought and heat stress. Having been shown to improve plant stand and yield of chickpea in other environments, seed priming – soaking the seed overnight before surface drying and sowing the next day – was tested for its efficacy under Barind conditions.In the 1998–99 season, 30 trials grown entirely on residual soil moisture were conducted in farmers' fields. A statistically significant mean yield response to priming of 47% was obtained. In 1999–2000, 105 on-farm trials and 15 demonstrations comparing presence and absence of priming were conducted. The crop received rain during this growing season. In a randomly chosen subset of 35 trials, scientists recorded a mean yield increase due to priming of 20%; it was 22% (from 1.02 to 1.25 t ha−1) in the remaining 64 trials (6 of the 105 trials were abandoned) where farmers recorded yields. Using a different variety, the mean yield response to priming in 15 demonstrations was 17% (from 1.25 to 1.46 t ha−1).The priming response was attributed mainly to rapid seedling establishment, with higher plant stand and earlier crop maturity allowing escape from end-of-season stresses. Priming also reduced the incidence of stem and root diseases, and increased nodulation by native rhizobia. This simple technology can substantially increase chickpea yields to remunerative levels for the resource-poor farmers in this difficult environment. Further, it is suggested that this technology can act as a catalyst for the introduction of further technologies that will permit reliable and profitable cultivation of post-rainy-season crops and thus improve the livelihoods of the rural population.

Responses of potato (Solanum tuberosum) to potassium fertilizers

Between 1989 and 1999, 33 experiments tested the effects of potassium (K) fertilizer on the yield and quality of potatoes. The experiments were done on a range of soil types and used varieties and management conditions common to modern commercial production. The average yield in these experiments was 48 t/ha. Nearly half of the experiments were done on soils that had exchangeable K values < 120 mg/l (MAFF Indices 0–1) but use of K fertilizer resulted in statistically significant increases in fresh weight yield in only seven experiments. Generally, soil exchangeable K was a poor predictor of the probability of a yield response. Potassium fertilizer caused an increase in dry weight yield in only four experiments and these experiments were characterized by the absence of irrigation, soils with small amounts of exchangeable K and use of determinate varieties. Re-examination of published data supported the findings in the current work: potatoes are not particularly responsive to K fertilizer and the optimal K application rate is rarely > 170–210 kg K/ha. When applied at the optimal rate, the effects of K fertilizer on tuber dry matter concentration were nonsignificant. Exceeding the optimal K application rate caused occasional reductions in tuber dry matter concentrations particularly if potassium chloride (KCl) was used. In the two experiments where it was tested, application rate and form of K had no effect on crisp fry-colour. The effect of K fertilizer on tuber K concentration was measured in 21 experiments and on average each tonne of fresh weight yield was associated with 4·2 kg K. The range in values was large, 2·8–5·7 and related to soil exchangeable K.For fertilizer recommendations based solely on the probability of a significant yield response to K fertilizer it is suggested that no more than 210 kg K/ha be applied even on soils with < 120 mg exchangeable K/l. For fertilizer recommendations based on crop K removal, an uptake value of 4·8 kg K/t fresh weight (FW), as has been suggested, would be adequate, although errors in the estimation of yield may lead to over or under application of K. Since there was little evidence to support fertilizer policies that apply more K than is removed by the crop a fertilizer recommendation system based primarily on the probability of a yield response would be more than sufficient.

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.

On-Farm Starter Fertilizer Response in No-till Corn

Even though recent experiments in the southern Corn Belt have shown that corn (Zea mays L.) yield responses to starter fertilizer are fairly common in no-till management systems, few producers in this region use starter fertilizer. Producer skepticism about the applicability of small-plot research to production situations is one reason for this lack of adoption. Several experiments have suggested that N is the most important nutrient for producing yield responses, while others have indicated that P is important as well. The objective of this research was to (i) validate at a field scale no-till corn yield and economic response to starter fertilizer and (ii) determine the relative importance of N and P in producing this yield response. During a 3-yr period, six replicated strip trials were conducted in production cornfields comparing no starter to three categories of starter fertilizer: traditional low N/high P 2 O 5 , medium N/medium P 2 O 5 , and N-only. Significant positive yield responses to starter fertilizers were observed in all six experiments. Yield differences between the three categories of starter fertilizer were minimal, and not statistically significant when averaged across locations. The average of all starter categories and experiment locations showed that starter fertilizer increased yield by 13 bu/acre. Use of starter fertilizer for no-till corn appears to be a profitable practice under production-field conditions in the southern Corn Belt. Nitrogen-only starter was the most profitable because it had the lowest material cost and produced the same yield as the P-containing starters.

Greenbug Resistance Management on Sorghum with Insecticide Mixtures: a Biological and Economic Analysis

Several tactics were evaluated for insecticide resistant greenbug, Schizaphis graminum (Rondani), control on sorghum. During the first 2 yr of this research, control by chlorpyrifos, carbofuran, and malathion and mixtures of the latter 2 chemicals plus piperonyl butoxide with chlorpyrifos were compared on sorghum. Chlorpyrifos provided <60% control. The mixtures of chlorpyrifos + carbofuran or malathion provided good control of insecticide resistant greenbug. The mixture of chlorpyrifos + piperonyl butoxide provided mediocre control of resistant greenbugs. In 1996, an experiment was designed to evaluate the effects of greenbug population insecticide resistance ratio and preexposure of greenbugs to chlorpyrifos on control by mixtures of chlorpyrifos with carbofuran or malathion. About half of the plots were presprayed with chlorpyrifos (0.28 kg [AI]/ha) 4 d before applying individual insecticides or mixtures. Plots were infested with 2 ratios of resistant: susceptible greenbugs (1:3 and 3:1, respectively). Application of mixtures of chlorpyrifos + malathion provided best control followed by chlorpyrifos + carbofuran and chlorpyrifos. Prespraying greenbugs with chlorpyrifos did not affect their control with subsequent insecticide resistance management mixtures. The difference between the 2 ratios was significant with the lowest greenbug densities in plots dominated by susceptible individuals. There was a significant yield response to greenbug densities. The highest yields were obtained in plots sprayed with chlorpyrifos + malathion mixtures. When chlorpyrifos was applied to greenbug populations dominated by resistant aphids, yields were lower than in the infested control plots where greenbugs were not sprayed. Economic analysis of the data further demonstrated the advantage of the chlorpyrifos + malathion mixture for controlling insecticide resistant greenbug.

Nitrogen Availability and Leaching from Soil Amended with Municipal Solid Waste Compost

AbstractBeneficial use of municipal solid waste compost depends on identifying a management strategy that supports crop production and protects water quality. Effects of compost and N fertilizer management strategies on corn (Zea mays L.) yield and NO−3‐N leaching were evaluated in a 3‐yr study on a Hubbard loamy sand soil (sandy, mixed, Udorthentic Haploboroll). Two composts were each applied at either 90 Mg ha−1 yr−1 from 1993 to 1995, or at 270 Mg ha−1 in one application in 1993. The compost and non‐amended plots were sidedressed annually with N fertilizer as urea at 0, 125, and 250 kg ha−1. Biochemical properties of the compost as well as compost management strongly affected crop response and fate of N. Compost increased grain yield with no significant yield response to N fertilizer with the single compost application in Year 1 and the annual compost application in Year 3. Plant N uptake increased with N fertilizer rate, except in the 270 Mg ha−1 compost treatments in Year 1. Over the 3‐yr period, NO−3‐N leaching with the 270 Mg ha−1 compost application was 1.8 times greater compared to that with the annual application. The estimated N mineralization ranged from 0 to 12% and 3 to 6% in the annual and single compost addition, respectively. Under the conditions of this study, annual compost application with reduced supplemental N fertilizer was the best management strategy to reach optimum crop yield while minimizing NO−1‐N leaching losses.

Manure and fertilizer contributions to soil mineral nitrogen and the yield of forage maize

Fifteen field trials were conducted to evaluate soil mineral N measurement as a means for quantifying the total N supply to forage maize and so to form the basis for fertilizer recommendations on a crop-specific basis. In every trial, 4 rates of cattle manure N (nominally 0, 80, 160, 240 kg N per ha) and 4 rates of ammonium nitrate (0, 50, 100, 150 kg N per ha) were factorially combined. Soil mineral N measurements were made before manure application, at the time of maize drilling, 7-10 weeks after drilling and after harvest. Measurements on control treatments which received no manure or ammonium nitrate showed extensive net mineralisation of soil N (mean 140 kg N per ha) in the 7-10 weeks after drilling followed by a decrease due to crop uptake, and probably net immobilisation, of approximately the same amount by harvest. This net mineralisation was probably the reason why only one trial showed a significant dry-matter yield response to ammonium nitrate. Results indicated that , to be useful for N recommendations, soil mineral N measurements should be taken 7-10 weeks after drilling. Only if the amount of mineral N at this time is less than expected crop N offtake should fertilizer N be applied. A mean of around 64% of the N applied in ammonium nitrate could be accounted for in soil mineral N after harvest of the maize, although this was reduced to 24% in the single trial where a dry-matter response to ammonium nitrate was recorded.

In-furrow Starter Fertilization Enhances Growth and Maturity in Early Sweet Corn

Field studies were conducted in 1994 and 1995 to evaluate the effects of in-furrow-placed (i.e., applied directly in the seed channel) starter fertilizer on the emergence, maturity, and yield response of early sweet corn. In both years, three starter fertilizer treatments were applied: APP, with N and P at 13 and 19 kg·ha-1, respectively (13N-19P kg·ha-1), either banded (5 cm below and 5 cm to the side of the seed) or placed in-furrow, and a control (no starter fertilizer). Additionally, in 1995, the rate of APP was increased to supply 26N-38P kg·ha-1 in combination with either band (5 × 5 cm) or in-furrow placement. Seedling emergence was delayed whenever starter fertilizer was applied with the seed; however, significant reductions (≈21%) in plant stand occurred only at the high rate of in-furrow placement. In both years, all starter treatments had a positive effect on seedling dry-matter production, and hastened silking. In-furrow application of 13N-19P kg·ha-1 increased marketable ear yields 34% in 1995, but had no effect in 1994. Lack of yield response to the high rate of in-furrow fertilizer in 1995 was primarily a function of reduced stand, as ear number and ear mass per plant, and average ear size were similar to those in the other starter treatments. Based on these results, in-furrow APP at 13N-19P kg·ha-1 appears to be an effective starter fertilization regime for early sweet corn, comparable in effect to banded 26N-38P kg·ha-1. However, high rates of in-furrow APP may reduce stands. Although significant yield response to in-furrow starter fertilizer may not always be realized, the increased early seedling growth may itself be a benefit, since fast-growing seedlings are more likely to be tolerant of adverse environmental conditions than are less vigorous plants. Chemical name used: ammonium polyphosphate (APP).

In-furrow Starter Fertilization Enhances Growth and Maturity in Early Sweet Corn

Field studies were conducted in 1994 and 1995 to evaluate the effects of in-furrow-placed (i.e., applied directly in the seed channel) starter fertilizer on the emergence, maturity, and yield response of early sweet corn. In both years, three starter fertilizer treatments were applied: APP, with N and P at 13 and 19 kg·ha-1, respectively (13N-19P kg·ha-1), either banded (5 cm below and 5 cm to the side of the seed) or placed in-furrow, and a control (no starter fertilizer). Additionally, in 1995, the rate of APP was increased to supply 26N-38P kg·ha-1 in combination with either band (5 × 5 cm) or in-furrow placement. Seedling emergence was delayed whenever starter fertilizer was applied with the seed; however, significant reductions (≈21%) in plant stand occurred only at the high rate of in-furrow placement. In both years, all starter treatments had a positive effect on seedling dry-matter production, and hastened silking. In-furrow application of 13N-19P kg·ha-1 increased marketable ear yields 34% in 1995, but had no effect in 1994. Lack of yield response to the high rate of in-furrow fertilizer in 1995 was primarily a function of reduced stand, as ear number and ear mass per plant, and average ear size were similar to those in the other starter treatments. Based on these results, in-furrow APP at 13N-19P kg·ha-1 appears to be an effective starter fertilization regime for early sweet corn, comparable in effect to banded 26N-38P kg·ha-1. However, high rates of in-furrow APP may reduce stands. Although significant yield response to in-furrow starter fertilizer may not always be realized, the increased early seedling growth may itself be a benefit, since fast-growing seedlings are more likely to be tolerant of adverse environmental conditions than are less vigorous plants. Chemical name used: ammonium polyphosphate (APP).

Effects of foliar fertilization of texas southern high plains cotton: Leaf phosphorus, potassium, zinc, iron, manganese, boron, calcium, and yield distribution1

Foliar fertilizers are often used in cotton (Gossypium hirsutum L.) production systems across the U.S. Cotton Belt. Their usefulness, however, in producing high yielding, high quality cotton remains to be resolved. This study was conducted to determine the effects of foliar fertilizers on cotton leaf phosphorous (P), potassium (K), zinc (Zn), iron (Fe), manganese (Mn), boron (B), and calcium (Ca) concentrations and yield distribution. During the 1990 growing season, this study was conducted at the Texas Tech University Research Farm east of New Deal, TX on a Pullman clay loam (fine, mixed, superactive thermic, Torrertic Paleustoll). Six foliar treatments were incorporated into a randomized complete block design with six blocks. Treatments 2(15–2–0 with Ca), 3 (8–32–5 with Mn, Fe, Zn, and B), and 4 [8–8–8 with Mn, Fe, Zn, B, and copper (Cu)] were commercial products and were applied according to their manufacturers recommendations. Treatments 5 and 6 (46–0–0) were applied at various rates. During the 1991 growing season, this study was conducted at an on‐farm location northeast of Petersburg, TX. The soil at this location was also a Pullman clay loam. The same six foliar treatments were incorporated into a randomized complete block design with four blocks. Foliar treatments were applied during both growing seasons at 0, 2, 4, 6, and 8 weeks after square initiation. One week after each treatment application, ten plants were removed from each plot and divided into three nodal horizons: (1) from node six to node nine, (2) from node ten to node thirteen, and (3) node fourteen and above. Leaf nutrient concentrations were determined by these nodal horizons. Numbers of first and second position fruit per plant were also determined within these nodal horizons. Leaf Zn, Fe, Mn, and B were increased by one of the commercial products in this investigation. However, none of these elements were deficient in the untreated plots and the observed increases were beyond the plant required concentrations. Cost‐benefit analyses were not conducted due to the lack of a significant yield response from the foliar fertilizers. We conclude that none of the costs associated with foliar fertilization will be recovered in net returns.

Meadow bromegrass response to coated and conventional urea fertilizers

In central Alberta, surface-broadcast urea is usually less effective in increasing grass forage yield than ammonium nitrate (AN) due to volatilization loss. A 2-yr field experiment was conducted in 1994 and 1995 on meadow bromegrass (Bromus bibersteinii Roem and Shult 'Regar') at Eckville, Alberta to compare a number of synthetic con-trolled-release urea fertilizers with conventional urea and AN fertilizers for their effect on dry matter yield (DMY), protein yield (PY), N-use efficiency (NUE) and percent N recovery (NR). The N fertilizers were applied at 100 kg N ha−1 in early June of 1994 and mid-April of 1995. The meadow bromegrass was harvested three times during the May to September growing season. In both years there was a significant forage yield response to applied N. In 1994, the DMY, PY, NUE and NR were similar for urea and AN, and most of the treated urea products were inferior to urea alone. This was most likely due to delayed application of N fertilizer until just before the start of summer rains. In 1995, urea had lower DMY (by 874 kg ha−1), PY (by 177 kg ha−1), NUE (by 8.8 kg DM kg−1 N ha−1) and NR (by 27.3%) than AN. Some of the coated urea products (e.g., Sh. 19, Sh. G) gave significantly greater DMY, PY, NUE and NR than urea alone, though still less than AN. These results suggest that under conditions when surface-applied urea is inferior to AN, its effectiveness can be improved by using Sh. 19 and Sh. G controlled-release urea fertilizers on grassland. The controlled-release fertilizers may be more expensive and therefore, additional cost must be considered as compared with AN before using on a commercial basis. Key words: Ammonium nitrate, bromegrass, controlled-release N fertilizers, forage yield, N recovery, urea

In-furrow Starter Fertilization Enhances Growth and Maturity in Early Sweet Corn

Field studies were conducted in 1994 and 1995 to evaluate the effects of in-furrow-placed (i.e., applied directly in the seed channel) starter fertilizer on the emergence, maturity, and yield response of early sweet corn. In both years, three starter fertilizer treatments were applied: APP, with N and P at 13 and 19 kg·ha-1, respectively (13N—19P kg·ha-1), either banded (5 cm below and 5 cm to the side of the seed) or placed in-furrow, and a control (no starter fertilizer). Additionally, in 1995, the rate of APP was increased to supply 26N—38P kg·ha-1 in combination with either band (5 × 5 cm) or in-furrow placement. Seedling emergence was delayed whenever starter fertilizer was applied with the seed; however, significant reductions (≈21%) in plant stand occurred only at the high rate of in-furrow placement. In both years, all starter treatments had a positive effect on seedling dry-matter production, and hastened silking. In-furrow application of 13N—19P kg·ha-1 increased marketable ear yields 34% in 1995, but had no effect in 1994. Lack of yield response to the high rate of in-furrow fertilizer in 1995 was primarily a function of reduced stand, as ear number and ear mass per plant, and average ear size were similar to those in the other starter treatments. Based on these results, in-furrow APP at 13N—19P kg·ha-1 appears to be an effective starter fertilization regime for early sweet corn, comparable in effect to banded 26N—38P kg·ha-1. However, high rates of in-furrow APP may reduce stands. Although significant yield response to in-furrow starter fertilizer may not always be realized, the increased early seedling growth may itself be a benefit, since fast-growing seedlings are more likely to be tolerant of adverse environmental conditions than are less vigorous plants. Chemical name used: ammonium polyphosphate (APP).

Toxicity of Minor and Micronutrients in Cranberry

Cranberry showed significant yield response to applied fertilizer. Some growers apply large quantities of some minor and micronutrients in an effort to increase yields. Tissue levels for nutrient sufficiency and excess have been determined in cranberry, but toxicity levels have not been determined. We exposed rooted cuttings of `Stevens' cranberry (Vaccinium macrocarpon Ait.) to high concentrations of individual nutrients in solution culture and then aeroponics. Shoot boron concentration rose rapidly, but not root concentration. At 300 ppm boron, leaf necrosis appeared and dry weight accumulation slowed. Copper and zinc accumulated in roots, but not in tops and thus will be difficult to diagnose. Shoot growth slowed with elevated root copper. Sulfur accumulated quickly in shoots and reduced growth when it exceeded 0.65%. These tissue levels are far higher than historical results from grower samples.

Nitrogen Effects on Triticale Grain Yield, Amino Acid Composition, and Feed Nutritional Quality for Swine

Nitrogen fertilizer recommendations for triticale (X Triticosecale Wittmack) and soft red winter (SRW) wheat (Triticum aestivum L) in the southeastern USA are similar in spite of different end uses. Grain yield, protein, and amino acid composition of four triticale cultivars were evaluated over five N levels ranging from 30 to 150 Ib/acre in four Georgia environments. Nitrogen was topdressed as ammonium nitrate at peak tillering. Relative economic value of triticale for feed was calculated assuming total replacement of corn (Zea mays L) plus variable amounts of soybean [Glycine max (L.) Merr.] meal (SBM) in a standard swine diet formulated to 100% of National Research Council (NRC) lysine requirement at representative prices for corn and SBM. Significant grain yield responses to N occurred in three of the four environments. Grain yield was maximized with 90 or 120 lb N/acre depending on environment and cultivar. Yield component responses to N were increased tiller density, decreased seeds per head, and decreased seed weight. Quantity of all amino acids increased linearly with N indicating potential for enhancing nutritional value by increasing N to raise contents of limiting essential amino acids. The superior lysine content of triticale relative to corn resulted in a relative cash price for triticale, which averaged 6% higher than corn value (range 3% to 10%). Despite N-induced increases in lysine content and relative nutrional value of triticale for feed, marginal return per acre was maximized at N levels associated with maximum grain yield. Cultivars varied for all traits except tiller density. Maximum economic return per acre was obtained with improved cultivars Florico and Florida 201, which had higher yield potential and test weight, but lower lysine content, than cultivars Beagle 82 and Morrison. Based on our study using 1997 prices, current N recommendations for small grains of 60 to 120 lb N/acre depending on previous crop, are appropriate for triticale. At these N levels, cultivar selection is more important for increasing returns than additional inputs of N.

Critical Tissue Concentration and Chloride Requirements for Wheat

AbstractPrevious research in the Pacific Northwest and Great Plains has provided evidence that wheat (Triticum aestivum L.) yields are often improved by Cl− fertilization. Published reports on critical tissue concentrations and Cl− requirements for wheat are few in number. Our objectives were to define a critical plant Cl− concentration (head emergence) for maximum yield, develop a Cl− fertilizer recommendation, and determine the effect of Cl− fertilizer on grain protein. Thirty‐two field experiments (18 winter and 14 spring wheat) were conducted in Montana between 1988 and 1995. Experiments included comparisons with multiple cultivars and Cl− rates (0–90 kg ha−). Relative yield vs. plant Cl− concentration relationships were assessed from 219 cultivar × experiment episodes. Three zones of Cl− status were identified: (i) a deficiency zone, plant Cl− &lt;1.0 g kg−1, where significant (P &lt; 0.10) yield responses to applied Cl− occurred in 59 of 86 episodes (69%); (ii) an adequate Cl− status zone, plant Cl− ≥4.0 g kg−1, where yield responses occurred in only 2 of 44 episodes (&lt;5%); and (iii) a critical range between these two zones, where responses were observed in 25 of 89 episodes (28%). Regression of plant Cl− concentration on soil (0–60 cm) plus fertilizer Cl− revealed that deficient, critical range, and adequate Cl− zones were associated with &lt;7.5, 7.5 to 32, and ≥33 kg Cl− ha−1, respectively. The proposed guideline for wheat is to add sufficient Cl− to reach the upper end of the critical range (4.0 g kg−1 plant Cl−). This recommendation ensures adequate Cl− nutrition for maximum yield and kernel weight, although at some sites a slight reduction in grain protein (0.5%) may result.