Presidedress soil nitrogen test for corn in Virginia

Abstract

The presidedress soil nitrate test (PSNT) and the presidedress tissue nitrogen test (PTNT) have been developed to assess residual soil nitrogen (N) sufficiency for corn (Zea mays L.) in the humid eastern U.S. We conducted field studies at 47 sites during 1990 and 1991 to evaluate the use of the PSNT and PTNT for corn in Coastal Plain, Piedmont, and Appalachian Ridge and Valley regions of Virginia. Seven rates of fertilizer N (0, 45, 90, 135, 180, 225, and 270 kg/ha) were applied at corn height of 0.40 to 0.50 m and replicated four times in a randomized complete block design. Whole corn plants and soil to a depth of 0.30 m were sampled when corn height was 0.15 to 0.30 m to estimate available soil N prior to the application of fertilizer N treatments. Corn grain yield response to fertilizer N was used to assess residual soil N availability. Nitrogen concentration of whole corn plants at 0.15 to 0.30 m height was not an accurate indicator of plant‐available soil N. Corn yields were maximized without sidedress N at the 19 sites where soil NO₃‐N was at least 18 mg‐kg^‐1 and at the 17 sites where soil (NO₃+NH₄)‐N was at least 22 mg‐kg^‐1. The PSNT predicted corn N sufficiency regardless of soil physiographic region or surface texture; however, the critical values for NO₃‐N and (NO₃+NH₄)‐N were 3 to 5 mg‐kg^‐1 lower than those established in Pennsylvania and Maryland, where cooler soil temperatures may permit greater residence time of inorganic N.     

Poultry litter effects on unmanaged pasture yield,nitrogen and phosphorus uptakes,and botanical composition

Abstract

The poultry industry must dispose vast amounts of waste, mainly litter (PL), generated during production processes. This study was conducted to investigate the short‐term effects of various rates of PL application, i.e., cumulative 2‐year totals of 9.9, 19.4, 29.3, 39.0, and 48.9 mt ha^‐1, to unmanaged pasture on a Starr clay loam (fine‐loamy mixed thermic Fluventic Dystrochrepts). Dry matter yield, N and P concentrations, and changes in botanical composition were measured on a mixed species, tall fescue (Festuca arundinacea Schreb.) and bluegrass (Poa pratensis L.) pasture. Dry matter yields (r² = 0.99*), N uptake (r² = 0.99*), and P uptake (r² = 0.99*) increased curvilinearly with rate of PL application in both years. Yield increase was attributed to correction of N deficiency in pasture by the PL application. Lower levels of PL increased forage yields in 1992 compared with 1991, due to the residual effect of unmineralized N from PL applied in 1991. Nitrogen concentration in tissue increased with levels of PL application but P tissue concentration was not similarly affected. Based on environmental and economic considerations, the PL application rate of 11.4 mt ha^‐1 in 1991 followed by 8.0 mt ha^‐1 in 1992 was the most effective for pasture renovation when compared with the recommended inorganic N and P fertilizer rate. Forage yields on this treatment were 21.5 mt ha^‐1 versus 21.7 mt ha^‐1 for the inorganic N and P fertilizer treatment. All rates of applied PL increased the percentage of tall fescue (from approximately 50 percent to > 80 percent) and decreased the percentage of bluegrass in this mixed pasture. Rates of PL application of 22.9 mt ha^‐1 and above temporarily depressed plant growth. This research indicates that PL properly tested and applied at appropriate rates is a suitable source of fertilizer for pasture renovation and production.     

Nitrogen requirements associated with improved conservation tillage for corn production

Abstract

Excessive soil erosion and use of nitrogen fertilizer are costly to the Atlantic Coastal Plain corn (zea mays L., ’Funks G 4507') producer and both may serve to create environmental hazards. An in‐row chisel (36 cm deep) tillage method was compared with the standard 5 cm fluted coulter method for planting corn in premature wheat (Triticim aestivum L.) residues grown on an Orangeburg sandy loam (Typic Paleudult). Five orthogonal N levels ranging up to 440 kg of N/ha were used to determine an economic N optimum for each tillage method.

The in‐row chisel tillage method provides a possible yield advantage in the Atlantic Coastal Plain because of observed restricting soil layers within the normal corn rooting zone. The estimated profit‐maximizing quantities of N fertilizer were 262 and 295 kg of N/ha (234 and 263 1b of N/acre) for the fluted coulter and in‐row tillage procedures, respectively. Corn grain yields associated with these inputs were 9.6 × 10³ and 12.6 × 10³ kg/ha (153 and 200 bu/acre), respectively. The yield increase associated with in‐row chiseling through a 2.5 metric ton mulched surface is attributed to potentially improved rooting and more efficient water storage and use.     

Relationships between nitrogen rate,plant nitrogen concentration,yield and residual soil nitrate‐nitrogen in silage corn

Abstract

Nitrogen (N) fertilizer is a key factor of yield increase but also an environmental pollution hazard. The sustainable agriculture system should have an acceptable level of productivity and profitability and an adequate environmental protection. The objectives of this study were to determine the relationships between N rate, DM yield, plant N concentration (NC) and residual soil nitrate‐nitrogen in order to improve the predicted N rate in corn (Zea mays L.) silage. The experiment was conducted over a period of three years in the province of Quebec on three soil series in a continuous corn crop sequence. Treatments consisted of six rates of N: O, 40, 80, 120, 160, and 200 kg N ha^‐1 as ammonium nitrate applied at planting: broadcast and side banded. Four optimum N rates were calculated using different models: (i) economic rate base on fertilizer and corn price using the quadratic model (E); (ii) economic rate based on fertilizer and corn price using the quadratic‐plus‐plateau model (QP); (iii) critical rate based on linear‐plus‐plateau model (P); (iv) lower than maximum rate (L) corresponding to 95% of maximum yield. The optimum plant NC at all growing stages and the N uptake at harvest were calculated depending on these N rates and yields.

The NC of whole plant at 8‐leaf stage (25–30 cm plant height) of ear leaf at tasselling and of whole plant at harvest stage, the N rate, the N uptake at harvest and the DM yield were all significantly intercorrelated and affected by soils and years, but not affected by N fertilizer application method. The DM yield was linearly and significantly related to NC of whole plant at 8‐leaf stage (rv = 0.932**). At this stage, the average NC corresponding to the optimum N rate and yield was of 3.71, 3.68, and 3.66% as calculated with E, L, and P model, respectively. Our data suggest that the NC of whole plant at 8‐leaf stage may be used to evaluate the N nutrition status of plant and the required optimum N fertilizer rate. The NC of ear leaf at tassel stage was also significantly correlated to corn yield (r = 0.994**). It may be used as an indicator to evaluate the near‐optimum N rate in the subsequent years.

The N uptake by whole above‐ground plant at harvest was quadratically related to corn yield. Data show that at high fertilizer N rate, the N uptake still increased without significantly increasing yield. The N uptake was of 176.5, 163.0, and 155.0 kg N ha^‐1 using the E, L and P rates of 146, 126, and 115 kg N applied ha^‐1, respectively. The optimum N rate and yield were affected by soil type and year, but not by the method of N fertilizer application. The yield increased rapidly up to a N rate of about 120 kg N ha^‐1 and then quite slightly to a maximum N rate of 192 kg N ha^‐1. The optimum N rate was of 115 and 126 kg N ha^‐1 using the P and L model respectively and as high as 146.8 kg N ha^‐1 using the E model. The L model, using a much smaller N rate, gave a reasonably high yield compared to E rate (12.2 and 12.5 Mg ha^‐1, respectively). The data show that a relatively much lower N rate than maximum did not proportionally diminish the yield. Thus, for a difference of 40.4% between maximum N rate and P rate a difference of only 7.4% in yield was observed. Using the L model the differences in rate and yield were of 34.4% and 4.7%, respectively. The QP model gave no significant difference compared to E model.

At harvest the residual soil NO₃‐N increased significantly with increasing N fertilizer rate in whole of the 100 cm soil profile, but mainly in the top 40 cm soil layer. The total NO₃‐N found in 0–100 cm profile at rate of 0, 120 and 200 kg applied N ha^‐1 at planting was as high as 33.7, 60.5, and 74.5 kg N ha^‐1 respectively in a light soil and 37.5, 97.5, and 145.5 kg N ha^‐1 in a heavy clay soil. The difference in NO₃‐N content in the 60–100 cm layer between different applied N rate suggests that at harvest, part of fertilizer N applied at planting was already leached below the 100 cm soil layer. Results, thus, show that reasonably high corn yields can be obtained using more adequate N fertilizer rates which avoid the overfertilization and are likely to reduce the air and ground water pollution.     

Grain yield,stalk rot,and mineral concentration of fertigated corn as influenced by N P K

Peanut (Arachis hypoaaea L.) is a major cash crop in Georgia. Corn (Zea mays L.) is the preferred rotation crop, but is often not profitable because of large inputs costs. Fertilizer comprises approximately 50% of the variable production costs of irrigated corn. There is interest in reducing fertilizer inputs, in particular N, to reduce variable costs and decrease nitrate leaching to groundwater, but yields may suffer. Our objective was to investigate the effect of N, P, and K fertilizer rates on the yield of N‐fertigated corn in a corn/peanut rotation. Field experiments were conducted during 1987 and 1988 on a Tifton loamy sand (fine‐loamy, siliceous, thermic Plinthic Paleudult) at Tifton, GA. Treatments were three rates each of N, P, and K fertilizer in a complete factorial. Nitrogen, P, and K rates were 168, 252, 336 kg N ha^‐1 yr^‐1; 44, 73, 103 kg P ha^‐1 yr^‐1; and 84, 223, and 363 kg K ha^‐1 yr^‐1, respectively. Grain yields were large, 12.6 and 10.4 Mg ha^‐1 in 1987 and 1988, respectively, but not affected by N, P, or K rate. Since the lower rates of N, P, and K were less than recommended, fertilizer use efficiency for fertigated corn can be improved, for at least one year, by reducing N, P, and K fertilizer rates to less than current recommendations. Rates of N, P, and K did not result in a substantial difference in the concentration of essential nutrients. Stalk rot was limited (< 15%), but decreased with increasing K fertilizer rate.     

Impact of organic and inorganic fertilizers on yield,taste, and nutritional quality of tomatoes

In a greenhouse experiment, tomato plants were grown in sand culture to test whether different fertilization regimes (mineral or organic fertilizers) at low (500 mg N plant^–1 week^–1) and high (750 mg N plant^–1 week^–1) nitrogen levels affected yield, nutritional quality, and taste of the fruits. In the mineral‐fertilizer treatments, nitrate‐ or ammonium‐dominated nutrient solutions were used. Organic fertilizer was supplied as fresh cut grass‐clover mulch (a total of 2.4 kg and 3.6 kg were given per plant at low and high N level, respectively) without (orgN) and with additional sulfur fertilization (orgN+S). Yields of red tomatoes from the organically fertilized plants were significantly lower (1.3–1.8 kg plant^–1) than yields from plants that received mineral fertilizer (2.2–2.8 kg plant^–1). At the final harvest, yields of green tomatoes in the organic treatment with extra sulfur were similar (1.1–1.2 kg plant^–1) to the NO ‐dominated treatments at both nutrient levels and the NH ‐dominated treatment at high nutrient level. Organic fertilizers released nutrients more slowly than mineral fertilizers, resulting in decreased S and P concentrations in the leaves, which limited growth and yield in the orgN treatments. Analysis of tomato fruits and plants as well as taste‐test results gave no conclusive answer on the relationship between sugar or acid contents in the fruits, macronutrient content of plant leaves and fruits, and perceived taste. Sugar contents were higher in the fruits given mineral fertilizer, whereas acid contents were higher in the fruits given organic fertilizer. Preference in taste was given to the tomatoes from plants fertilized with the nitrate‐dominated nutrient solution and to those given organic fertilizer with extra sulfur. Thus, a reduction in growth, which was expected to lead to a higher concentration of compounds like sugars and acids, did not result in better taste. Overall, it can be concluded that an appropriate nutrient supply is crucial to reach high yields and good taste.     

On‐farm comparison of variable rates of nitrogen with uniform application to maize on canopy reflectance,soil nitrate,and grain yield

Recent development in canopy optical‐sensing technology provides the opportunity to apply fertilizer variably at the field scale according to spatial variation in plant growth. A field experiment was conducted in Ottawa, Canada, for two consecutive years to determine the effect of fertilizer nitrogen (N) input at variable‐ vs. uniform‐application strategies at the V6–V8 growth stage, on soil mineral N, canopy reflectance, and grain yield of maize (Zea mays L.). The variable N rates were calculated using an algorithm derived from readings of average normalized difference vegetation index (NDVI) of about 0.8 m × 4.6 m, and N fertilizer was then applied to individual patches of the same size of NDVI readings (0.8 m × 4.6 m) within a plot (2184 m²). Canopy reflectance, expressed as NDVI, was monitored with a hand‐held spectrometer, twice weekly before tasseling and once a week thereafter until physiological maturity. Soil mineral N (0–30 cm depth) was analyzed at the V6 and VT growth stages. Our data show that both variable and uniform‐application strategies for N side‐dressings based on canopy‐reflectance mapping data required less amount of N fertilizer (with an average rate of 80 kg N ha^–1 as side‐dressing in addition to 30 kg N ha^–1 applied at planting), and produced grain yields similar to and higher nitrogen‐use efficiency (NUE) than the preplant fully fertilized (180 kg N ha^–1) treatment. No difference was observed in either grain yield or NUE between the variable‐ and uniform‐application strategies. Compared to unfertilized or fully fertilized treatments, the enhancements in grain yield and NUE of the variable‐rate strategy originated from the later N input as side‐dressing rather than the variation in N rates. The variable‐rate strategy resulted in less spatial variations in soil mineral N at the VT growth stage and greater spatial variations in grain yield at harvest than the uniform‐rate strategy. Both variable‐ and uniform‐application strategies reduced spatial variations in soil mineral N at the VT stage and grain yield compared to the unfertilized treatment. The variable‐rate strategy resulted in more sampling points with high soil mineral N than the uniform‐rate strategy at the VT stage.     

Influence of nitrogen fertilization,tillage, and residue management on a soil nitrogen mineralization index

Abstract

Nitrogen, tillage, and residue management systems influence the ability of microorganisms to mineralize plant residues in soil. The objective of this research was to investigate the seasonal changes in autoclave extractable‐N (AN) as influenced by different N rates, tillage practices and residue management systems. A field study under a continuous corn rotation was initiated in 1980, with factorial combinations of 2 or 20 g N/m², roto‐tillage or no‐tillage, and residue (corn stover) returned or removed treatments. Soil water, AN, and inorganic N were measured at regular intervals over a three‐year period (1984 to 1986). AN, as a soil N mineralization index, was shown to be sensitive to changes in the nitrogen, tillage, and residue management systems. Correlations between corn yields and the N mineralization index suggest that AN was sampling a biologically‐active N pool.     

Dicyandiamide (DCD) research in agriculture in the mid‐Atlantic region

Abstract

Numerous experiments have been conducted in Maryland and Pennsylvania since 1981 to determine if adding the nitrification inhibitor dicyandiamide (DCD) to an ammonium‐containing or producing N fertilizer source would increase the efficiency of that source with turfgrass, wheat, or corn. Greater yields per unit of fertilizer N were attained in three of eight experiments with wheat when DCD was included with an early spring application of N as urea or UAN. There was no significant beneficial effect of DCD on turf clipping yields or color in the 3 years of the turf study or on corn grain yields in the 22 field comparisons of N fertilizer with and without DCD. In five of the 22 comparisons with corn, there was a significantly lower grain yield with DCD than when it was not included. In three of these five cases, it was hypothesized that the lower yields with DCD were due to increased NH₃ volatilization from urea or urea‐ammonium nitrate solutions containing DCD that were surface‐applied to no‐till corn. It was concluded that there was little likelihood that the inclusion of a nitrification inhibitor such as DCD with N fertilizer would increase N fertilizer efficiency with corn or turf on the predominantly well‐drained silt loam soils in the two states.     

Border row effect on corn grain response to sidedressed nitrogen fertilizer

Abstract

Nitrogen (N) fertilizer recommendations for corn (Zea mays L.) are normally developed from field experiments that determine yield response to applied N. The objective of this study was to examine the severity of border row competition with the harvest rows for sidedressed N in field experiments measuring grain yield. This study was conducted in 1993 and 1994 on a Sharpsburg silty clay loam (fine, montmorillonitic, mixed, mesic argiudoll). Ammonium nitrate was broadcast to the center two rows of a four row plot, all four rows of a four row plot and all six rows of a six row plot. Results showed that grain yield from four and six row plots were similar and indicated that while grain yields were much less in 1993 than 1994 (7.36 versus 12.06 Mg ha^‐1, respectively), corn yield response to N was similar regardless of the number of rows fertilized. Thus, there is little reason for plots larger than four rows. The results also lend credibility to sidedressing only harvest rows for soil test calibration studies where grain yield response is the primary response variable.     

By-Plant Prediction of Corn (Zea mays L.) Grain Yield using Height and Stalk Diameter

Methods for determining midseason nitrogen (N) rates in corn have used the parameter normalized difference vegetation index (NDVI) and, in some cases, plant height. The objective of this study was to analyze the relationship of stalk diameter along with predictors of yield, including NDVI and plant height with grain yield. Five site-years of data were analyzed, where several rows of corn plants were selected, and yield from plants within the row was recorded individually. Measurements of stalk diameter, plant height, and NDVI were taken from growth stages V8–VT. Using a value of stalk diameter × plant height gave the best correlation with grain yield (r² = 0.34, 0.55, 0.67; V8, V10, V12, growth stages respectively). This work showed that stalk diameter × plant height was positively correlated with by-plant corn grain yields, and this parameter could be used for refining midseason fertilizer N rates for growth stages V8–V12.     

Nitrapyrin,terrazole, atrazine and simazine influence on denitrification and corn growth

In modern agriculture, long‐term soil fertility and crop productivity are maintained by a combination of inorganic fertilizers and pesticide inputs which, in turn, create environmental and health concerns. Therefore, studies were initiated to evaluate two commonly used herbicides (atrazine and simazine) and two biological nitrification inhibitors (nitrapyrin and terrazole) applied with NO₃‐N source fertilizer for their effects on denitrification and on corn (Zea mays L.) growth and yields. Each chemical applied at the rate of 10, 50, or 100 mg a.i. L^‐1 suppressed denitrification of NO₃ ^‐ in a liquid medium inoculated with a Tifton loamy sand in a laboratory study. Nitrapyrin and terrazole selectively suppressed NO₃ ^‐ or NO₂ ^‐ or both reduction while atrazine and simazine suppressed NO₂ ^‐ or N₂O or both reduction. In greenhouse pot culture studies, chemical application resulted in higher percent N recovery relative to the control. When atrazine or simazine was part of the chemical treatment, concentrations of NO₃ ^‐ and NO₂ ^‐ in corn (Zea mays L.) plants increased, and plant growth was restricted due to NO₂ ^‐ toxicity. During two consecutive years of field studies using split‐banded applications of N fertilization with nitrapyrin and terrazole, corn ear yields increased 78% and 25% in the first and second year, respectively. With atrazine and simazine, however, yields increased significantly in the first season only. Mixing either herbicide with nitrapyrin or terrazole had no effect on yields during both seasons.

Chemical Names: atrazine = [2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine]; simazine = [2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine]; nitrapyrin = [2‐chloro‐6‐(trichloromethyl)pyridine]; terrazole = [ethoxy‐3‐trichloromethyl‐1,2,4‐thiadiazole].     

MAIZE GRAIN YIELD RESPONSE TO VARIABLE ROW NITROGEN FERTILIZATION

Crop yields are affected by the rate and method of nitrogen (N) fertilizer application. This study was conducted to determine the effects of applying variable N rates by row on maize grain yields. The effects of variable rates and row application were investigated at the R.L. Westerman Irrigation Research Facility near Stillwater, Oklahoma on a Port-Oscar silt loam (fine-silty, mixed, super active, thermic Cumulic Haplustolls) and at Hennessey, Oklahoma on a Bethany silt loam (fine, mixed, thermic Pachic Paleustolls). For 2005 that was characterized by high yields, significant yield differences occurred in non-fertilized rows adjacent to N (67, 100, 134 kg N ha^?1) fertilized rows, but not when adjacent to low N [34 and 67 (some cases) kg N ha^?1]. In 2006, which had a dry growing season, grain yields were significantly lower than those produced in 2005. With few exceptions, rows receiving N did not produce significantly higher yields in 2006. In 2007, trends were similar to those observed in 2005. Excluding 2006, all site-years showed a significant reduction in yield when N fertilizer was not applied to each row. In order to maximize corn grain yields, N fertilizer should be applied by row, while alternate row N application should be avoided.     

Evaluation of Nutrasweet sludge as a nitrogen fertilizer for corn and wheat

Abstract

NutraSweet sludge, a by‐product of the production of the noncarbohydrate sweetener aspartame, is often used as a N fertilizer for crops. However, its performance with respect to inorganic N fertilizers is not well understood. This work was conducted to compare NutraSweet sludge to ammonium sulfate and urea as an N fertilizer for wheat and corn. Samples from two soils were mixed with one of the three N sources to achieve rates of 0, 25, 50, 100, or 150 mg N kg^‐1. The treated soil was placed in pots, which were used to grow corn or wheat for 45 days in the greenhouse. Above‐ground dry matter yields of com and wheat increased as N rate increased from 0 to 50 or 100 mg N kg^‐1. Above 100 mg N kg^‐1, dry matter yields decreased. In general, at a given N rate, NutraSweet sludge produced dry matter yields that were equal to or higher than those obtained with ammonium sulfate or urea. The results suggest that NutraSweet sludge could be managed as an ammoniacal N fertilizer when applied to crops.     

Cover crop nitrogen availability to conventional and no‐till corn: Soil mineral nitrogen,corn nitrogen status,and corn yield

Abstract

Understanding seasonal soil nitrogen (N) availability patterns is necessary to assess corn (Zea mays L.) N needs following winter cover cropping. Therefore, a field study was initiated to track N availability for corn in conventional and no‐till systems and to determine the accuracy of several methods for assessing and predicting N availability for corn grown in cover crop systems. The experimental design was a systematic split‐split plot with fallow, hairy vetch (Vicia villosa Roth), rye (Secale cereale L.), wheat (Triticum aestivum L.), rye+hairy vetch, and wheat+hairy vetch established as main plots and managed for conventional till and no‐till corn (split plots) to provide a range of soil N availability. The split‐split plot treatment was sidedressed with fertilizer N to give five N rates ranging from 0–300 kg N ha^‐1 in 75 kg N ha^‐1 increments. Soil and corn were sampled throughout the growing season in the 0 kg N ha^‐1 check plots and corn grain yields were determined in all plots. Plant‐available N was greater following cover crops that contained hairy vetch, but tillage had no consistent affect on N availability. Corn grain yields were higher following hairy vetch with or without supplemental fertilizer N and averaged 11.6 Mg ha^‐1 and 9.9 Mg ha^‐1 following cover crops with and without hairy vetch, respectively. All cover crop by tillage treatment combinations responded to fertilizer N rate both years, but the presence of hairy vetch seldom reduced predicted fertilizer N need. Instead, hairy vetch in monoculture or biculture seemed to add to corn yield potential by an average of about 1.7 Mg ha^‐1 (averaged over fertilizer N rates). Cover crop N contributions to corn varied considerably, likely due to cover crop N content and C:N ratio, residue management, climate, soil type, and the method used to assess and assign an N credit. The pre‐sidedress soil nitrate test (PSNT) accurately predicted fertilizer N responsive and N nonresponsive cover crop‐corn systems, but inorganic soil N concentrations within the PSNT critical inorganic soil N concentration range were not detected in this study.     

Short-Term Effects of Poultry Litter Application On Silage Maize Yield and Soil Chemical Properties

If properly managed, poultry litter (PL) might be a good alternative to conventional fertilizers. This paper reports on a three-year field study to compare the effects of two consecutive PL and traditional mineral fertilizer applications on silage maize (Zea mays) production and soil chemical properties. The experiment was undertaken on volcanic soil in the Central-South Region of Chile. The PL was applied at doses of 10, 15 and 20 Mg ha^?1, with and without mineral fertilizer to 50 m² plots, and the outcomes compared with those obtained with two rates of nitrogen mineral fertilizer equivalent to the mid and high PL rates. Maize yield showed a positive response to all treatments, although the mean yield obtained with the PL treatments was higher than with the mineral fertilizer in the third year, in which no fertilizers were applied. The whole plant N concentration of the PL plants was significantly higher than that of the plants that received mineral fertilizer (this was the only nutrient variable for which such differences were found), but the values were not related to the amount of PL applied. After two annual applications of PL, slight increases in soil-available inorganic N and P were observed. However, the values obtained were low, highlighting the high P fixation capacity of the soil as well as its high capacity to stabilise organic matter. No other soil variables studied were significantly affected by any of the treatments.     

Effect of sulfur rate,application method,and source on yield and mineral content of corn

Abstract

Corn (Zea mays L.) grown on sandy Coastal Plain soils may be subject to sulfur (S) deficiency due to the low levels of available S in the soil. The diagnosis of S deficiency in the field is sometimes ambiguous since mineralization of soil organic matter or root growth into the subsoil may supply adequate S to the crop. Yield response to S fertilizers has been more frequent since incidental additions of S to the soil by air pollution and fertilizer applications have been reduced. This study was conducted to identify S deficiency in corn grown on sandy Coastal Plain soils and to determine the effects of S source, rate and method of application on grain yield. Irrigated corn was grown on Norfolk loamy sand and Tifton loamy sand near Leesburg and Moultrie, Georgia, respectively in 1987. Grain yields were increased with addition of 11 kg S ha^‐1 compared to the check treatment. Increased rates of S up to 88 kg ha^‐1 did not increase grain yields above the 11 kg ha^‐1 rate. There was no difference between banded or broadcast application of (NH₄)₂SO₄ or between elemental S and (NH₄)₂SO₄ as S sources. Earleaf S concentrations of 1.6 g kg^‐1 and extractable soil S concentrations of 4.0 to 8.7 mg kg^‐1 were associated with S deficiency. Visual symtoms of S deficiency were observed in the check treatments throughout the growing season at both experimental sites. The results indicate that visual symptoms and tissue analysis can be used to identify S deficiency. Extractable soil S may be useful in determining the possible response to S fertilizer especially if the subsoil is sampled.     

Long‐term fertilization impacts on corn yields and soil organic matter on a clay‐loam soil in Northeast China

A long‐term fertilization experiment with monoculture corn (Zea mays L.) was established in 1980 on a clay‐loam soil (Black Soil in Chinese Soil Classification and Typic Halpudoll in USDA Soil Taxonomy) at Gongzhuling, Jilin Province, China. The experiment aimed to study the sustainability of grain‐corn production on this soil type with eight different nitrogen (N)‐, phosphorus (P)‐, and potassium (K)–mineral fertilizer combinations and three levels (0, 30, and 60 Mg ha^–1 y^–1) of farmyard manure (FYM). On average, FYM additions produced higher grain yields (7.78 and 8.03 Mg ha^–1) compared to the FYM0 (no farmyard application) treatments (5.67 Mg ha^–1). The application of N fertilizer (solely or in various combinations with P and K) in the FYM0 treatment resulted in substantial grain‐yield increases compared to the FYM0 control treatment (3.56 Mg ha^–1). However, the use of NP or NK did not yield in any significant additional effect on the corn yield compared to the use of N alone. The treatments involving P, K, and PK fertilizers resulted in an average 24% increase in yield over the FYM0 control. Over all FYM treatments, the effect of fertilization on corn yield was NPK > NP = NK = N > PK = P > K = control. Farmyard‐manure additions for 25 y increased soil organic‐matter (SOM) content by 3.8 g kg^–1 (13.6%) in the FYM1 treatments and by 7.8 g kg^–1 (27.8%) in the FYM2 treatments, compared to a 3.2 g kg^–1 decrease (11.4%) in the FYM0 treatments. Overall, the results suggest that mineral fertilizers can maintain high yields, but a combination of mineral fertilizers plus farmyard manure are needed to enhance soil organic‐matter levels in this soil type.     

Previous Corn Row Effects on Potassium Nutrition and Yield of Subsequent No‐Till Soybeans

Abstract

Narrow‐row soybean [Glycine max (L.) Merr.] production in corn [Zea mays L.]–soybean rotations results in various distances of soybean rows from previous corn rows, yet little is known about soybean responses to proximity to prior corn rows in no‐till systems. The objective of this study was to evaluate the impacts of preceding corn rows on potassium (K) nutrition and yield of subsequent no‐till soybeans. Four field experiments involving a corn–soybean rotation were conducted on long‐term no‐till fields with low to medium K levels from 1998 to 2000 near Paris and Kirkton, Ontario, Canada. In the corn year, treatments included K application rate and placement in conjunction with tillage systems or corn hybrids. Before soybean flowering, soil exchangeable K concentrations (0–20 cm depth) in previous corn rows were significantly higher than those between corn rows. At the initial flowering stage, trifoliate leaf K concentrations of soybeans in preceding corn rows were 2.0 to 5.3 g kg^?1 higher than those from corresponding plants between corn rows. Yield of no‐till soybeans in previous corn rows increased 10 to 44% compared to those between previous corn rows. Positive impacts of prior corn rows on soil K fertility, soybean leaf K, and soybean yield occurred even when K fertilizer was not applied in the prior corn season. Deep banding of K fertilizer tended to accentuate row vs. between‐row effects on soybean leaf K concentrations in low‐testing soils. Corn row effects on soybeans were generally not affected by either tillage system or corn hybrid employed in the prior corn crop. Potassium management strategies for narrow‐row no‐till soybeans should take the potential preceding corn row impacts on soil K distribution into account; adjustments to current soil sampling protocols may be warranted when narrow‐row no‐till soybeans follow corn on soils with low to medium levels of exchangeable K.     

Effets des engrais N,P et K sur le rendement et la qualite de l'ensilage ue mais

Abstract

Thirteen fertility trials were made throughout Quebec's corn growing region during 1972–74. These included eleven fertilizer combinations with corn silage as the test crop and were carried out on nine soils. Total dry matter and digestible nutrients (TDN) varied greatly from year to year, though, mean yields increased by 23 and 30 percent respectively with the 50 kg N/ha treatment, compared to control receiving no nitrogen fertilization. However, 150 kg N/ha was required to attain a maximum yield of 1250 kg/ha crude protein. Despite a 0.2 percent nitrate content found in the silage grown on the most northerly site, a 120 kg P/ha combined with 100 kg N and K gave the highest mean TDN production (9580 kg/ha).

Potassium fertilization affected plant K content of corn grown at the most northerly site only, where a 0.5 percent was found with the control on a suit containing low potassium levels. Further, striking increases in Ca and Mg concentrations were observed with corn grown on that soil. However, magnesium concentration ranging from 0.11 to 0.14 percent were found with nine field trials out of twelve. Also, low K:(Ca + Mg) ratios were found on three trials, which were increased with potassium fertilization levels of 150 kg K/ha. Accordingly, it is suggested that uptakes of 200, 48, 200, 30 and 30 kg/ha of N, P, K, Ca and Mg are required for good corn silage crops.