Preplant Application Research Articles

Reducing Johnsongrass (Sorghum halepense) Interference in Corn (Zea mays) with Herbicides and Cultivation

Field studies were conducted in 1990 and 1991 to evaluate johnsongrass control and interference in corn using combinations of nicosulfuron, EPTC + dichlormid, and cultivation. Nicosulfuron applied to 30-cm-tall rhizome johnsongrass provided greater control and corn yield than a later application to 60-cm-tall johnsongrass. Johnsongrass control and corn yield within the later nicosulfuron treatment were improved by a preplant application of EPTC. EPTC and/or cultivation alone provided less johnsongrass control and lower corn yield than nicosulfuron or handweeding.

Control of Rice Water Weevil with Fipronil Applied Preplant Incorporated, 1994

Abstract Three rates of fipronil (EXP60655A 1.5G) applied preplant and lightly incorporated were compared with carbofuran (Furadan 3G) and an untreated check for control of RWW. Experimental design was a RCB with 4 replications. Plot size was 9 rows (7 inch row spacing) × 16 ft. Rice was drill-seeded in a Crowley silt loam at 110 lb/acre 12 May and emerged 20 May. Fipronil was applied broadcast with a hand shaker and lightly incorporated with a hand rake on 12 May. Propanil and thiobencarb at 2 lb (AI)/acre each and bentazon at 1 lb (AI)/acre were applied 1 Jun. Permanent flood was applied on 13 Jun. Nitrogen was applied in a 3-way split of 120 lb/acre on 13 Jun and 30 lb/acre each on 15 and 26 Jul. Furadan 3G was applied broadcast with a hand shaker on 20 Jun. On 5 and 12 Jul five 4 × 4 inch (diam by depth) soil cores were removed from each plot. Soil was washed from plant roots into 40-mesh screens. Screens were immersed in salt water and RWW immatures were recovered and counted. The center 4 rows × 12 feet of plots were harvested on 27 Sep with a small plot combine. Reported yields were adjusted to 12% moisture.

Irrigated Spring Wheat Response to Topdressed Nitrogen as Predicted by Flag Leaf Nitrogen Concentration

Topdressed N is frequently applied to irrigated hard red spring (HRS) wheat (Triticum aestivum L.) in an effort to increase grain protein content (GPC). However, the actual need for supplemental N could be better defined if the probability of a response was referenced to some measure of plant N status. This study was conducted to determine whether flag leaf N (FLN) concentration at heading could be used to estimate the potential for increasing GPC with topdressed N. Field studies were conducted in 1989, 1990, and 1991 on a Declo silt loam (coarse loamy, mixed, mesic Xerollic Calciorthid). Two HRS wheat varieties (Copper and Pondera) received preplant applications of either 0, 60, 120, or 180 lb N/acre to produce a range of FLN concentrations at heading. Plants at each N level were top-dressed with either 0, 20, or 40 lb N/acre 1 to 2 d after heading. Topdressed N had relatively little effect on grain yield or test weight. Flag leaf N concentrations and GPC were both increased by preplant and topdressed N applications, however. Grain protein contents of both varieties were positively correlated with N concentrations of flag leaves sampled prior to N top-dressing. Grain protein content of low N plants (3.0 to 3.6% N) was increased by 1.0 to 1.5% with 20 lb N/acre topdress applications and 2.0 to 2.5% with 40 lb N/acre applications. Increases in GPC resulting from N topdressing decreased linearly as FLN at heading increased. Plants with FLN concentrations above 4.2% did not benefit from topdressed N. Results of this study provide preliminary evidence that FLN concentration can provide a good indication of the likelihood of a response to topdressed N. Research Question Irrigated hard red spring wheat growers are encouraged to split N applications during the growing season to increase grain protein content (GPC) and N-use efficiency. Split N applications could be managed more effectively if there was a predictive tool available to correlate plant N status with the potential for a GPC response to N topdressing. The primary objective of this research was to evaluate flag leaf N (FLN) concentration as a more precise predictor of GPC response to N topdressing. Literature Summary Studies conducted with irrigated and nonirrigated wheat production systems have shown that wheat GPC can be influenced by late split N applications. Responses are especially effective when application is made between heading and flowering. The response becomes limited, however, if plant N status is high. Pacific Northwest wheat growers frequently apply late-season N fertilizer in hopes of obtaining a GPC response. Few studies have been completed which provide growers with information to predict a response to these late N fertilizer applications. Study Description Two irrigated hard red spring wheat cultivars were planted in combination with four preplant and three topdressed-N fertilizer rates in each of 3 yr at Aberdeen, ID. Wheat varieties: Copper and Pondera, 110 lb/acre in 7 in. row Soil: Declo silt loam Fertility: Idaho Soil Test Irrigation: Sprinkler irrigation Weed control: Bromoxynil and MCPA Treatments: N was applied preplant at either 0, 60, 120, or 180 lb N/acre Topdressed N rates of 0, 20, or 40 lb N/acre were applied at heading N fertilizer: Ammonium nitrate (34-0-0) Flag leaf N sampling: Heading (Zadoks 59) and early milk (Zadoks 73) Sample size: 25 flag leaves/plot Applied Question Is FLN concentration at heading a good predictor of GPC response to topdressed N in irrigated hard red spring wheat? When hard red spring wheat plants were topdressed with N at heading, there usually was an increase in GPC. This increase was closely related to FLN concentration at heading. Nitrogen topdressing increased GPC of low N plants (3.0 to 3.6% N) by 1.0 to 2.5%. As FLN at heading increased, the GPC response to topdressed N became progressively smaller. Plants with FLN concentrations above 4.2% generally did not respond to topdressed N. Heading is an appropriate sampling time since topdressed N is often applied during flowering. The relationships between FLN and GPC may differ between locations, soil moisture conditions, and other environmental factors. Therefore, local calibration of FLN relationships with yield and GPC probably will be required for specific production areas. Recommendations We recommend that growers who have a desire to increase GPC with late season N applications use FLN concentrations at heading as an appropriate predictor for response.

Nitrogen Use Efficiency of Split Nitrogen Applications in Soft White Winter Wheat

AbstractNitrogen use efficiency (grain weight per unit of N supplied from soil or fertilizer) can be reduced by overfertilization, suboptimal yields, and N losses. Nitrogen is typically fall‐applied in eastern Washington for soft white winter wheat (Triticum aestivum L.) production, and is therefore subject to overwinter losses or accumulation in deep soil layers. Increasing grain protein levels of soft white winter wheat have been attributed in part to excessive N application rates and high residual N levels. Spring N applications were evaluated over four site‐years as an option to all‐fall applied N for reducing N inputs and improving N use efficiency, thereby allowing producers to maintain productivity while controlling grain protein. Five to six N rates ranging from 0 to 140 kg ha−1 for the all‐fall N applications were compared with fall‐spring split applications of 84 to 140 kg total N ha−1. Nitrogen was applied in the spring by topdressing (TD) or with a spoke‐wheel point‐injection (PI) system. A 15N experiment was conducted at two locations during the second year to quantify N uptake from fertilizer and soil N. High preplant residual N conditions resulted in limited responses to added N. Nitrogen use efficiency was 26 to 44% lower in the 140 kg ha−1 fall‐applied N treatments than in the zero‐N control. Reduced N use was related to N losses from the system and to decreased N utilization efficiency (grain weight produced per unit plant N). Spring‐applied N, with point injection or topdressing, maintained or increased N use efficiency compared with equivalent all‐fall N rates of 84 and 112 kg N ha−1. More 15N‐labeled fertilizer (7–16% more) was recovered with a split N application than with fall‐applied N at the same total rate of 112 kg N ha−1. At maturity, 68% of plant N was from soil sources with a split application, compared with 80% with an all‐fall application. These results suggest spring‐N applications with point injection or topdressing can improve fertilizer N recovery and N use efficiency over preplant applications in dryland winter wheat.

652 PB 028 COMPUTER ANALYSIS OF AERIAL PHOTOGRAPHS TO DETECT N STRESSES IN LETTUCE

Lettuce (Lactuca Sativa L.) produced in the low desert typically shows large yield responses to N fertilization. Concern about the potential threat of nitrate-N to ground water prompted the state of Arizona to pass legislation aimed at implementing improved N management practices. Nitrogen management guidelines recommended by the University of Arizona for lettuce suggest a preplant application based on a soil nitrate-N test and subsequent sidedress applications based on plant tissue monitoring. However, growers have some anxiety that close adherence to recommendations resulting from an average plant sample may compromise crop uniformity. Aerial photographs have the potential to detect differences in N status in any portion of the field. This study evaluated digital computer analysis of aerial photographs as a tool for evaluating the N status of lettuce. The digitized photographs appeared to detect deficiencies not apparent to the human eye. There were good correlations (R2 0.83 to 0.99) between Gray-scale ratio and N status, suggesting digital analysis of aerial photographs has potential for diagnosing N deficiencies in lettuce.

Pruebas en el combate de malezas en ají dulce en 1991 y 1992

En 1991 y 1992 se realizaron dos experimentos de campo en la Estación Experimental Agrícola en Lajas para combatir las malezas en siembras de ají dulce. En el primer experimento, el mejor tratamiento fue el uso de cubierta plástica en el banco más paraquat como posemergente en aplicación directa entre los bancos. Napropamide a razón de 2.24 kg ia/ha y clomazone a razón de 1.12 kg ia/ha aplicados presiembra, seguidos por paraquat a razón de 0.56 kg ia/ha, controlaron las malezas menos eficientemente que la cubierta plástica más paraquat. En el segundo experimento la cubierta plástica más paraquat fue el mejor tratamiento. Las aplicaciones presiembra y posemergente a las malezas de glifosato o paraquat a las dosis recomendadas controlaron las malezas satisfactoriamente. Con el tratamiento de cubierta plástica más paraquat dirigido se obtuvo el mejor rendimiento de ají dulce. Los tratamientos presiembra y posemergente de glifosato o paraquat también controlaron las malezas bien. En ambos experimentos el tratamiento integrado de cubierta plástica más paraquat produjo un rendimiento de ají dulce significativamente mayor que los demás tratamientos.

Manure and Fertilizer Effects on Alfalfa Plant Nitrogen and Soil Nitrogen

Applying manure to alfalfa (Medicago sativa L.) poses a potential risk for overloading the soil system with N. The objective of this study was to evaluate the effect of preplant nutrient treatments on alfalfa herbage and crown root N and soil nitrate-N. The effects of three preplant manure rates (3 000, 6 000, and 12 000 gal/acre) and three equivalent P and K fertilizer rates were investigated at Rosemount and Waseca, MN, on a Waukegan silt loam (fine-silty over sandy or sandy skeletal, mixed mesic Typic Hapludolls) and on a Nicollet clay loam (fine-loamy, mixed, mesic Aquic Hapludolls), respectively. Alfalfa herbage N removal was highly correlated to herbage dry matter yield. Herbage N removal in the establishment year was greater for the manure treatments than the P and K fertilizer treatments at the Rosemount sites. The average herbage N removal in the seeding year was 229 lb N/acre for Rosemount-North and in the production year was 278, 341, and 233 lb N/acre for Rosemount-South, Rosemount-North, and Waseca, respectively. Measured soil nitrate-N in plots receiving manure peaked 30 to 50 d after manure application, averaging 328 lb/acre, and decreased throughout the growing season. Peak nitrate-N amounts were proportional to the amount of manure applied. After the second alfalfa growing season, soil nitrate-N amounts were not significantly different among treatments. This study's data indicate that preplant manure applications do not result in consistently more N in the soil or in the plant after 2 yr of alfalfa. Research QuestionDairy producers in the Upper Midwest have traditionally applied manure to corn ground. When manure storage capacity or handling systems necessitate, manure is often topdressed on alfalfa. Because topdress manure is often detrimental to alfalfa, preplant applications warrant consideration. The primary objective of this research was to evaluate the effect of preplant manure and fertilizer P and K treatments on N removal by alfalfa and soil nitrate-N amounts during 2 yr of alfalfa production. Literature SummaryNumerous surveys have documented the overapplication of N on corn fields in traditional dairy livestock enterprises. This, along with the necessity of summer manure applications, has prompted some farmers to apply manure on alfalfa. While alfalfa has been shown to use residual soil N, alfalfa herbage production and N removal in association with soil N levels created by manure additions are important due to the environmental concerns of excess N in the soil system. The effects of manure-N on plant and soil N accumulation need further investigation. Study DescriptionOur study was conducted in southeast Minnesota on one site that tested “medium” and two sites that tested “very high” for P and K. Three rates of manure (3 000, 6 000, and 12 000 gal/acre) and three equivalent rates of P and K fertilizer, along with a control, were applied preplant for a 2-yr stand of alfalfa. Applied QuestionsIs N removal by alfalfa or accumulation in the soil affected by manure application rate? Nitrogen removal by alfalfa was positively correlated with forage yield. In the season following the seeding year, manure rate did not have an effect on herbage N removal at the Rosemount sites, which had high P and K soil tests (Fig. 1). The lack of herbage N removal differences indicates that plant N fixation may have varied among plots. At Waseca, with the medium-testing soils for P and K, both manure and fertilizer treatments increased herbage N removal in proportion to the application rate in the production year. Soil nitrate-N amounts decreased rapidly the first summer after appliction for all sites (Fig. 2). After an increase in soil nitrate-N for the control and 3 000 gal/acre treatment in the spring of the second season, nitrate-N amounts decreased and by the end of the second season the soil nitrate-N amounts for the manure treatments and the control were similar. In the establishment year, the soil nitrate-N increases combined with herbage N removal could not account for all of the applied N in manure—total or inorganic. This indicates that appreciable amounts of N can be immobilized, denitrified, or volatilized after application. Fig. 1Herbage N removal in the year following seeding as affected by preplant manure or fertilizer treatments. Fig. 2Soil nitrate-N amounts (0–2 ft) averaged across all three sites as influenced by rate of manure application and time after application.

Use of Drainage Lysimeters to Evaluate Nitrogen and Irrigation Management Strategies to Minimize Nitrate Leaching in Maize Production

Increasing public awareness of nitrate contamination of groundwater has caused agriculturalists to focus their attention on nitrogen recommendations and management strategies. In Michigan the problem of nitrate contamination of groundwater is pervasive. Using drainage lysimeters placed in a growers field, a conventional nitrogen fertilizer and irrigation strategy was compared with a conservative research strategy for impact on yield and nitrate leaching in maize (Zea mays L.) production. The conventional nitrogen fertilizer strategy was to apply 178 kg N ha1 preplant as anhydrous ammonia and then some additional N in the starter fertilizer. Irrigation water applications for the conventional strategy were based on an irrigation scheduling program and the physical limitations of the existing center pivot system. The research strategy was to use split applications of nitrogen fertilizer and to apply irrigation water based on daily crop requirements. The research plot was outside of the influence of the growers irrigation system and had its own dedicated irrigation system which provided flexibility in the timing and amount of water applied. The two strategies resulted in similar yields for two seasons. However, the conventional plot received an additional 89 kg N/ha1 (preplant) in the first year due to operator error. During the first 24 months, the total drainage from the conventional strategy was 190 mm more than the research strategy and the nitrate leached was 170 kg N ha1 more. In the third year of the study, the preplant application of the conventional strategy was deleted and only 9 kg N ha1 was applied in the starter fertilizer. This was done to study the ability of maize to mine the soil nitrogen and reduce nitrate leaching. The research strategy was continued as in years past. Though only 9 kg N ha1 of nitrogen were applied to the conventional plot, the grain yield was 4445 kg ha1 and the nitrate leaching was reduced to 43 kg N ha1 over an eight-month period. That represented a reduction in nitrate leaching of 60% as compared to the same time period in the previous year. This study has shown the usefulness of drainage lysimeters in evaluating nitrogen and irrigation management strategies in respect to soil water drainage and nitrate leaching. Additionally, the collection of data throughout the year provides greater insight into non-growing season drainage, showing that most nitrate loss occurs between the harvest date and the subsequent planting date.

Preplant Manure and Commercial P and K Fertilizer Effects on Alfalfa Production

Many dairy producers are being forced to consider applying manure onto their alfalfa (Medicago sativa L.) acres because of environmental concerns regarding overapplication of manure on their corn (Zea mays L.) acres. We compared the use of manure and commercial fertilizer prior to establishment on alfalfa herbage yield and nutrient concentrations. Three rates of manure (3000, 6000, and 12000 gal/acre) were broadcast and incorporated before the direct-seeding of alfalfa. Three commercial fertilizer treatments also were applied to provide P and K application rates similar to those in the manure. At all sites, establishment-year yields from the manure and fertilizer treatments were equal to, or greater (0-103%) than, the control yield. With «very high» soil P and K tests, production-year yields were similar for the manure and fertilizer treatments [...]

Urea-Ammonium Nitrate Management Techniques for Winter Wheat Production

Wet soils, a consequence of poor drainage common to soils in the winter wheat (Triticum aestivum L.) producing areas of the southern Midwest USA, frequently hamper spring topdress fertilizer applications and reduce N efficiency. This 2-yr field study was an effort to identify alternative N management techniques that could be successfully implemented at either preplant or topdress application time. The effects of urea-ammonium nitrate (UAN) time of application, method of application, and rate of dicyandiamide (DCD) nitrification inhibitor on the flag leaf N, grain N, and grain yield of winter wheat were measured in 1990 and 1991 at the University of Illinois Brownstown Agronomy Research Center on a Cisne silt loam soil (fine, montmorillonitic, mesic Mollic Albaqualf) []

Nitrogen Management in Furrow Irrigated, Ridge-Tilled Corn

Use of conservation tillage methods, including ridge-tillage increases crop residue cover which can increase loss of urea-based fertilizers. Objectives of this study were to evaluate N sources, rates, methods, and times of application for ridge-tilled, furrow-irrigared corn (Zea mays L.) on a Crete silt loam soil (fine, montmorillionic, mesic Pachic, Argiustoll) near Scandia, KS. When averaged over 5-yr, grain yields were less with urea-ammonium nitrate (UAN) broadcast and dribbled treatments than with anhydrous ammonia (AA) preplant knifed, 28% UAN solution preplant knifed, and split applications of UAN knifed or dribbled. Surface dribbled UAN proved to be no more effective than surface broadcasting [...]

Re-Seeding Wheat (Triticum aestivum) Following Preplant Treatments of Atrazine

When applied correctly, atrazine can be used safely in certain areas of the United States for weed control in winter wheat, but persistence in the soil may injure wheat replanted after crop failure. Studies were conducted at Moro, OR, in 1989–90 and 1990–91 to determine the effect of September preplant applications of atrazine at 0.56, 1.12, and 2.24 kg a.i. ha-1 (1X, 2X, and 4X label rates) on wheat seeded at that time and on wheat re-seeded 2 or 6 mo later. Yield of winter wheat re-seeded in November following September atrazine applications was not reduced at any rate. The September-planted wheat was killed with glyphosate in the spring to simulate winter killing, then plots were re-seeded to spring wheat. The commercial rate of atrazine, 0.56 kg ha-1, caused only minor injury to spring wheat, but injury at the 2X and 4X rates was excessive.

TOMATO FERTIGATION

Tomato trials with black plastic mulch, drip irrigation, and fertigation were conducted on a Lily sandy loam soil of medium fertility at Crossville, TN in 1990 and 1991. 'Mountain Pride' tomatoes were fertilized with a broadcast preplant application of 1120 kg ha–1 of 10-4.4-8.3 fertilizer with and without combinations of black plastic mulch and weekly applications of 0.64 cm of water for 12 weeks through drip irrigation. Three black plastic mulch and drip irrigation treatments supplied additional nitrogen and potassium fertilizer through the drip irrigation system. Yields were increased by use of black plastic mulch and by trickle irrigation in 1991. However, additions of fertilizer through drip irrigation had no effect on yields.

Nitrogen Fertilization of Spring Wheat by Point-Injection

Point-injection is a new method of fertilizer application with possible advantages for wheat (Triticum aestivum L.) growing areas of the Northern Great Plains. A study was conducted to evaluate point-injection for N fertilization of spring wheat in southern Alberta. Field experiments at seven site-year combinations compared point-injection of urea NH4NO3 solution with the following conventional methods of granular N application: banded urea, banded NH4NO3, broadcast urea, and broadcast NH4NO3. Banded treatments were applied only as a preplant application, while broadcast and point-injection treatments were applied at one of five times, including preplant. There were no yield differences among any of the preplant application methods, nor was there a consistent significant difference among methods at individual sites. When averaged across sites and common application times, grain yields in point-injection treatments were 2 bu/acre higher than those in broadcast NH4NO3 treatments. Regardless of application method, wheat yields declined significantly when N was applied at the tillering stage or later. At three sites showing significant differences in 1989, grain yields in treatments receiving N at the five-leaf, tillering, booting, and flowering stages, averaged 98, 91, 81, and 70%, respectively, of those receiving N at seeding. At two sites, protein concentration was significantly increased by delaying application of N but protein yields were not increased because of lower grain yields. Point-injection is a viable alternative to conventional methods of N application for spring wheat. Because it provides effective N placement after seeding, point-injection affords some flexibility in application time and allows adjustment in fertilizer rates in accordance with growing conditions.

Response of Corn to Preplant Applications of Nitrogen and to Nitrogen Plus Nitrapyrin

Several factors, including N rate, N source, timing of application, and use of nitrification inhibitors, can influence yield and N-use efficiency of corn (Zea mays L.). A field experiment was conducted for 7 yr to determine if the use of nitrapyrin [2-chloro-6-(trichloromethyl) pyridine] applied with preplant, broadcast N applications as urea or urea-NH4NO3 (UAN) solution could influence corn grain yield, grain moisture at harvest, ear weight, and other parameters. A zero N check and two rates of N with and without nytrapyrin were applied on the same plots each year for 6 yr. In the seventh year, a crop was planted on the test area without N application to evaluate residual effects due to various treatments. A consistent yield response was observed to N in all years, including the residual year. The use of nitrapyrin increased yields with both N rates with the greatest benefit occurring at the lower of the two N rates. Additionally, the yield produced with nitrapyrin and the low N rate were consistently equal to yields produced with the high N rate without nitrapyrin. Yield differences resulted from a combination of increased ears per plot and increased ear weight. Both increasing N rate and use of nitrapyrin resulted in lower grain moisture levels in some years. In the residual year, yields were higher where N had been applied previously. Higher yields occurred where nitrapyrin had been used, suggesting greater N carryover from product use.

Control of purple nutsedge (Cyperus rotundus) in cotton with benfuresate

The herbicide benfuresate applied preplanting to cotton (Gossypium hirsutum L.) fields infested with purple nutsedge (Cyperus rotundus L.) inhibited nutsedge growth for several weeks and was found selective for cotton. The best nutsedge control was achieved when the herbicide was mechanically incorporated following a preplant broadcast or band application which was activated by a sprinkler irrigation. The rate of benfuresate needed for effective and selective nutsedge control in cotton ranged from 0.80 to 1.60 kg/ha, the higher rates necessary in soils with higher clay and organic matter contents.

The effect of nitrogen fertilizer and irrigation on black point incidence in soft white spring wheat

Agronomic studies were conducted to examine the effect of fertilizer N on black point incidence in Fielder soft white spring wheat (Triticum aestivum L. em Thell.). Black point incidence rose with increases in the amount of N supplied either as fertilizer applied during the growing season in irrigation water or as soil N, specifically nitrate, from fertilizer N application in previous years. A comparison of four different irrigation regimes demonstrated that black point incidence was highest under frequent irrigation (irrigate to field capacity at 75% available moisture) and lowest under conventional irrigation (irrigate to field capacity at 50% available soil moisture). In each irrigation regime, disease incidence increased as N rates were raised from 0 to 120 kg ha-1. A residual fertilizer-N study demonstrated in 1985 and 1986 that black point incidence generally rose with increasing levels of nitrogen from either preplant applications in the spring or soil nitrate from the previous year. However, additions of fertilizer N were shown to slightly reduce black point incidence at soil nitrate levels above 150 kg ha-1. A two-year fertilizer N study demonstrated that in treatments receiving the same amount (90 kg ha-1) of fertilizer N, the amount broadcast as a preplant treatment versus the amount applied in irrigation water in a fertigation treatment had no effect on black point incidence, but all fertilized treatments had significantly higher levels of disease than the unfertilized check.

Nitrogen Fertilizer Management Effects on Corn Grain Yield and Nitrogen Uptake

Concern about the fate of N remaining in the soil after harvest has heightened interest in management techniques that will increase the ability of a growing crop to use N. There is considerable interest in sidedressing or split-applying N fertilizer as an inexpensive way to increase fertilization efficiency and thus to reduce the amount of N not used by the crop. The response of continuous corn (Zea mays L.) to (NH4)2SO4 incorporated to a depth of 4 in. was studied during 1986 and 1987 at two sites in Iowa. Preplant and sidedress (V6 growth stage) N applications were combined to create 21 treatments with six rates ranging from 0 to 175 lb N/acre. Nitrogen rate significantly increased grain yield, leaf-N content, grain-N content, and N uptake at both sites in both years. Grain yields in 1986 ranged from 70 bu/acre to 187 bu/acre at Site 1, and from 76 bu/acre to 223 bu/acre at Site 2. Grain yields in 1987 ranged from 77 bu/acre to 146 bu/acre at Site 1 and from 51 bu/acre to 175 bu/acre at Site 2. The difference in maximum yields attained was probably due to differences in growing season rainfall. Two types of regression equations describing the relative effects of preplant and sidedress application of N on the variables studied were fitted to the data. The models had similar R2s and exhibited similar trends. There was no effect of time of N application except for Site 1 in 1986, where sidedress application significantly increased grain yield, N uptake in the grain, and leaf N content compared with preplant application. The data show that response to time of N application was site specific and directly and positively related to growing season rainfall, and that the response was not due to an increase in efficiency of use.

Effects of fertilizer rate, application timing and plant spacing on yield and nutrient content of bell pepper

Abstract Bell pepper (Capsicum annuum var annuum L.), cv Pip, transplants were established at 31 and 46 cm in‐rows on bare soil and drip irrigated on a twice weekly schedule. A base rate of fertilizer was applied either in one preplant application or in two (preplant and first flower set) or three (preplant, first flower set, after the midseason harvest) split applications. Additional fertilizer was applied in excess of the base rate on a predetermined schedule or after significant yield decline ('as needed'). Concentrations of 12 elements in leaf and fruit tissues were determined throughout the growing season. The three‐split application of the base rate of fertilizer increased total yield. Plants spaced at 46 cm had increased total and marketable yield in one year. Interactions of fertilizer treatment and plant spacing did not affect total yield. In one year when additional fertilizer was applied ‘as needed’, plants spaced at 31 cm produced more marketable yield than plants spaced at 46 cm. Nutrients in leaves and fruit did not respond to fertilizer treatment or spacing. In leaves and fruit, concentrations of elements increased, decreased/or stayed the same in both years. For leaves, exceptions were Cu, Mn, and N. For fruit, exceptions were Al, Fe, K, and N. A base level application of fertilizer applied preplant was sufficient to support marketable fruit production.

The Effect of Urea Application Systems on Grain Yield of Three Corn Hybrids

(.)The effects of N rate, time of application and the use of a nitrification inhibitor with urea were evaluated on a Dakota loam (fine loamy over sandy skeletal, mixed over silicious, mesic Typic Argiudoll) at River Falls, WI. Delaying N application from fall to side dress increased average yields from 103.7 to 113.5 bu/acre, with preplant applications yielding 110.4 bu/acre (.)