Feekes Stage Research Articles

In-season assessment of agronomic nitrogen use efficiency and its components in winter wheat using critical nitrogen dilution curve.

Accurate and timely nitrogen (N) scheduling requires knowledge of in-season crop N deficit. Therefore, understanding the association between crop growth and crop N demand during its growth period is imperative for fine-tuning N scheduling decisions to actual crop N demand and to enhance N use efficiency. The concept of the critical N dilution curve has been employed to assess and quantify the intensity and time of crop N deficit. However, research regarding the association between crop N deficit and N use efficiency in wheat is limited. The present study was carried out to determine whether there are relationships between the accumulated nitrogen deficit (Nand) and agronomic N use efficiency (AEN) as well as with its components (N fertilizer recovery efficiency (REN) and N fertilizer physiological efficiency (PEN)) of winter wheat and to explore the potential capacity of Nand for predicting AEN and its components. Data acquired from five variable N rates (0, 75, 150, 225, and 300kg ha-1) field experiments using six winter wheat cultivars were used to establish and validate the relationships between Nand and AEN, REN, and PEN. The results indicated that plant N concentration in winter wheat was significantly affected by N application rates. Nand varied from -65.73 to 104.37kg ha-1 after Feekes stage 6 under different N application rates. The AEN and its components were also affected by cultivars, N levels, seasons, and growth stages. A positive correlation was observed between Nand, AEN, and its components. Validation using an independent data set showed the robustness of the newly developed empirical models to accurately predict AEN, REN, and PEN with an RMSE of 3.43kg kg-1, 4.22%, and 3.67kg kg-1 and RRMSE of 17.53%, 12.46%, and 13.17%, respectively. This indicates that Nand has the potential to predict AEN and its components during the growth period of winter wheat. The findings will assist in improving in-season N use efficiency by fine-tuning N scheduling decisions in winter wheat cultivation.

Sulfur uptake and distribution, grain yield, and quality of hybrid and inbred winter wheat (Triticum aestivum L.) varieties under early and late waterlogging

AbstractBackgroundWaterlogging at early and later growth stages could affect sulfur (S) uptake, distribution, yield, and quality of winter wheat. We hypothesized that the hybrid winter wheat variety (Hyvento), with a high degree of heterosis and genetic diversity, is likely to uptake and utilize S more efficiently and withstands waterlogging better than the inbred wheat variety (Kredo).AimsThe objective of the present study was to investigate the effect of 2‐week waterlogging at the end of tillering stage (Feekes Stage 6) and/or ear emergence stage (Feekes Stage 10.1) on grain yield, yield components, S‐uptake and its partitioning, and composition of grain storage proteins (glutenins and gliadins) of hybrid (Hyvento) and inbred (Kredo) winter wheat varieties.MethodsPlants were grown in large containers (120 L) in a semi‐controlled greenhouse and harvested three times immediately after each waterlogging treatment and at agronomic maturity. Grain yield, S concentration in different plant organs, total protein content, and patterns of gluten proteins (gliadin and glutenin) and their subunits (by sodium dodecyl sulfate–polyacrylamide gel electrophoresis) in grains were evaluated.ResultsGrain yield of the inbred variety was more negatively affected under early and late waterlogging than the hybrid variety and was associated with reduced grain size. The decline in grain yield was significantly higher under late waterlogging (30%–31%) than early waterlogging (17%–18%). Compared to the hybrid variety Hyvento, the waterlogging‐induced decline in S concentration in grains, husk, and straw was markedly lower in the inbred variety Kredo. While early waterlogging did not affect total grain protein content in either of the varieties, late waterlogging significantly reduced the total grain protein content (18%) in the inbred variety Kredo. Similarly, the grain gliadin content of the hybrid variety was not affected by both waterlogged conditions, whereas 32% and 23% reductions were recorded for the inbred variety under early and late waterlogging, respectively. Nevertheless, waterlogging significantly increased the proportion of S‐poor high‐molecular‐weight glutenin subunits and ω‐gliadin in the inbred variety.ConclusionIt could be inferred from the present study that hybrid winter wheat variety is relatively resistant to waterlogging than the inbred wheat variety, and thereby produces higher grain yield. Efficient uptake and metabolism of S could be one of the mechanisms conferring waterlogging resistance in winter wheat.

Use of an Active Canopy Sensor Mounted on an Unmanned Aerial Vehicle to Monitor the Growth and Nitrogen Status of Winter Wheat

Using remote sensing to rapidly acquire large-area crop growth information (e.g., shoot biomass, nitrogen status) is an urgent demand for modern crop production; unmanned aerial vehicle (UAV) acts as an effective monitoring platform. In order to improve the practicability and efficiency of UAV based monitoring technique, four field experiments involving different nitrogen (N) rates (0–360 kg N ha−1) and seven winter wheat (Triticum aestivum L.) varieties were conducted at different eco-sites (Sihong, Rugao, and Xinghua) during 2015–2019. A multispectral active canopy sensor (RapidSCAN CS-45; Holland Scientific Inc., Lincoln, NE, USA) mounted on a multirotor UAV platform was used to collect the canopy spectral reflectance data of winter wheat at key growth stages, three growth parameters (leaf area index (LAI), leaf dry matter (LDM), plant dry matter (PDM)) and three N indicators (leaf N accumulation (LNA), plant N accumulation (PNA) and N nutrition index (NNI)) were measured synchronously. The quantitative linear relationships between spectral data and six growth indices were systematically analyzed. For monitoring growth and N nutrition status at Feekes stages 6.0–10.0, 10.3–11.1 or entire growth stages, red edge ratio vegetation index (RERVI), red edge chlorophyll index (CIRE) and difference vegetation index (DVI) performed the best among the red edge band-based and red-based vegetation indices, respectively. Across all growth stages, DVI was highly correlated with LAI (R2 = 0.78), LDM (R2 = 0.61), PDM (R2 = 0.63), LNA (R2 = 0.65) and PNA (R2 = 0.73), whereas the relationships between RERVI (R2 = 0.62), CIRE (R2 = 0.62) and NNI had high coefficients of determination. The developed models performed better in monitoring growth indices and N status at Feekes stages 10.3–11.1 than Feekes stages 6.0–10.0. To sum it up, the UAV-mounted active sensor system is able to rapidly monitor the growth and N nutrition status of winter wheat and can be deployed for UAV-based remote-sensing of crops.

Nitrogen Management for Forage Winter Cereals in the Northeastern USA

Forage double cropping can be a beneficial practice for dairy farmers in the northeastern United States, providing an additional, harvestable crop plus many environmental benefits. Triticale (× Triticosecale Wittm.), winter wheat (Triticum aestivum L.), and cereal rye (Secale cereale L.) are forage double crop options in New York that require nitrogen (N) management. From 2013 to 2016, 62 N‐rate trials were conducted across New York with five N rates (0, 34, 67, 101, and 135 kg N ha−1) applied in four replications at spring dormancy break. Forage was harvested at flag‐leaf stage in May (Feekes stage 9). Soil samples were taken prior to N‐application at dormancy break. Management practices and field characteristics were evaluated as predictors (using classification tree analyses) for yield and the most economic rate of N (MERN) at dormancy break, determined using a quadratic plateau model. Approximately one‐third of the sites did not respond in yield to spring N application, averaging 4.3 Mg DM ha−1. Of the remaining sites, ∼80% had MERNs ranging from 47 to 112 kg N ha−1, averaging 77 kg N ha−1, with yields at the MERN from 2.2 to 6.9 Mg DM ha−1, averaging 4.2 Mg DM ha−1. Yield could not accurately be predicted statistically. However, low‐yielding sites lacked fall manure application and well‐drained soils. We conclude that forage winter cereal fields with well‐drained soils, recent manure applications, and timely planting may not need additional N at dormancy break, while others require approximately 19 kg N ha−1 per Mg DM ha−1.Core Ideas N management is needed for optimum performance of forage winter cereal crops in New York. Yields of 1.0 to 6.9 Mg DM ha−1 were found in New York (4.1 Mg DM ha−1 average). Winter cereals required approximately 19 kg of N per 1 Mg DM for optimum forage yield. Soil drainage, manure history, and planting date affected N needs. Nitrogen rates beyond plant needs for optimum yield can increase crude protein.

Spectral-temporal characterization of wheat cultivars through NDVI obtained by terrestrial sensors

ABSTRACT Remote sensing applications in agriculture are presented as a very promising reality, but research is still needed for the correct use of spectral data. The objective of this study was to evaluate the spectral-temporal patterns of eleven wheat cultivars (Triticum aestivum L.). The experiment was conducted in Cascavel, PR, in the year 2014. With the help of the GreenSeeker and FieldSpec 4 terrestrial sensors, spectral signatures were determined and the temporal profiles of the Normalized Difference Vegetation Index (NDVI) were created. Statistical differences between wheat cultivars were analysed using analysis of variance (ANOVA) and Scott-Knott test. Grain yields obtained with INSEY (In-Season Estimate of Yield) factors were correlated. NDVI normalized by degree-days accumulated from the Feekes growth stages 2 and 8 showed to be more consistent in the estimation of grain yield, explaining approximately 70% of the variation. At the Feekes stage 10.1, wheat cultivars presented different spectral patterns in the near and medium infrared bands. This suggests that these spectral bands can be used to differentiate wheat cultivars.

Effect of Pyrasulfotole Carryover to Peanut and Tobacco

In the southeastern United States, growers often double-crop soft red winter wheat with peanut. In some areas, tobacco is also grown as a rotational crop. Pyrasulfotole is a residual POST-applied herbicide used in winter wheat, but information about its effects on rotational crops is limited. Winter wheat planted in autumn 2014 was treated at Feekes stage 1 or 2 with pyrasulfotole at 300 or 600 g ai ha−1. Wheat was terminated by glyphosate at Feekes stage 3 to 4. Peanut was planted via strip tillage, while tobacco was transplanted into prepared beds after minimal soil disturbance. Peanut exhibited no differences in stand establishment, growth, or yield, and tobacco stand, growth, and biomass yields were not different from the nontreated control for any pyrasulfotole rate or treatment timing.

Effect of Application Timing on Winter Wheat Response to Metribuzin

Metribuzin will control many problematic weed species in winter wheat in the mid-Atlantic states, including herbicide-resistant biotypes, but it has not been recommended due to crop safety concerns. In a three-year trial, metribuzin was applied at 105 or 210 g ai ha−1to wheat at the PRE, 2-leaf (Feekes stage 1 to 2), early spring (Feekes stage 3 to 4), and late spring (Feekes stage 4 to 6) growth stages using wheat cultivars sensitive to metribuzin. Early spring applications had the least amount of injury, and injury at this timing was transient and yield was not reduced. Yield loss was observed with the other application timings in at least one out of three years. Rainfall shortly after application appears to increase the risk of wheat injury.

Nitrogen Nutrition Improves the Potential of Wheat (Triticum aestivum L.) to Alleviate the Effects of Drought Stress during Vegetative Growth Periods.

Efficient nitrogen (N) nutrition has the potential to alleviate drought stress in crops by maintaining metabolic activities even at low tissue water potential. This study was aimed to understand the potential of N to minimize the effects of drought stress applied/occur during tillering (Feekes stage 2) and jointing (Feekes stage 6) growth stages of wheat by observing the regulations and limitations of physiological activities, crop growth rate during drought periods as well as final grain yields at maturity. In present study, pot cultured plants of a wheat cultivar Yangmai-16 were exposed to three water levels [severe stress at 35–40% field capacity (FC), moderate stress at 55–60% FC and well-watered at 75–80% FC] under two N rates (0.24 g and 0.16 g/kg soil). The results showed that the plants under severe drought stress accompanied by low N exhibited highly downregulated photosynthesis, and chlorophyll (Chl) fluorescence during the drought stress periods, and showed an accelerated grain filling rate with shortened grain filling duration (GFD) at post-anthesis, and reduced grain yields. Severe drought-stressed plants especially at jointing, exhibited lower Chl and Rubisco contents, lower efficiency of photosystem II and greater grain yield reductions. In contrast, drought-stressed plants under higher N showed tolerance to drought stress by maintaining higher leaf water potential, Chl and Rubisco content; lower lipid peroxidation associated with higher superoxide dismutase and ascorbate peroxidase activities during drought periods. The plants under higher N showed delayed senescence, increased GFD and lower grain yield reductions. The results of the study suggested that higher N nutrition contributed to drought tolerance in wheat by maintaining higher photosynthetic activities and antioxidative defense system during vegetative growth periods.

Inheritance of resistance to Ug99 stem rust pathogen in selected barley lines

Stem rust (Puccinia graminis tritici) race Ug99 is a devastating disease of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). Barley is the world's fourth most important cereal crop after wheat, maize (Zea mays L.) and rice (Oryza sativa L.). The seedlings of F2 populations were inoculated 7–10 d after planting and when the first leaf was fully emerged (Feekes stage 1). The observed resistant (R):susceptible (S) ratio of the F2 populations HKBL-1385-13×08-UT-86 (χ20.05 = 0.480, P ≥ 0.488), HKBL-1385-13×09-N2-19 (χ20.05 = 0.641, P ≥ 0.424), ND2649 × 09-AB-78 (χ20.05 = 1.05, P ≥ 0.309) and ND25882×09-AB-78 (χ20.05 = 3.599, P ≥ 0.058) exhibited Mendelian segregation of 3R:1S suggesting that the resistance is conferred by major genes. In addition, F2 populations derived from the crosses Karne×09-N2-19 (χ20.05 = 1.343, P ≥ 0.246), Nguzo×09-AB-78 (χ20.05 = 0.429, P ≥ 0.512), ND26249×09-N2-52 (χ20.05 = 2.576, P ≥ 0.111) and ND25882×09-AB-78 (χ20.05 = 0.980, P ≥ 0.322) conformed to a phenotypic ratio of 9:7 indicating that there are genes modifying the resistance to Ug99. The results of this study suggest that there are valuable major genes for stem rust resistance that could be used to improve susceptible barley and wheat germplasm.

Nitrogen‐Fertilizer Equivalence of Poultry Litter for Winter Wheat Production

The N availability of manure applied to summer‐grown crops has been frequently researched, but information regarding the N‐fertilizer equivalence of manure for winter‐grown crops is lacking. Our objectives were to determine the inorganic N‐fertilizer value of poultry litter (PL) compared with applying urea‐N fertilizer to wheat (Triticum aestivum L.) in late winter and examine the inorganic‐N content in PL‐amended soils at 5, 15, and 25°C. Six field experiments compared PL applied preplant or at planting at 84 and 168 kg N ha−1 to wheat fertilized with urea–ammonium sulfate blend (UASB) rates of 0 to 191 kg N ha−1. The apparent N uptake efficiency of PL‐N ranged from 0 to 63 and 8 to 56% for wheat receiving 84 and 168 kg PL‐N ha−1, respectively. The time of PL application had no effect on wheat N uptake and yield at four of five sites. The mean potentially available N (PAN) values for N uptake at Feekes stage 10.5 and grain yield were 0.31 and 0.39 kg UASB‐N kg−1 PL‐N, respectively. Soil amended with PL incubated at 15 and 25°C showed that 19 to 31% of the added PL‐N was mineralized and recovered as NO3–N in 28 to 44 d. When the incubation temperature was reduced to 5°C, 17 to 19% of the PL‐N was recovered as NO3–N or NH4–N with <3% recovered as NO3–N. The results suggest winter wheat growers that apply PL in the fall can subtract 30 to 40% of the PL‐N from the late‐winter N fertilizer rate.

Traits associated with winter wheat grain yield in Central and West Asia

Improved adaptation of winter wheat (Triticum aestivum L.) to drought and heat may be influenced by days to heading, plant height, biomass, canopy temperature (CT) at grain filling, and rate of senescence. This study shows that, under supplemental irrigation or rainfed conditions, days to heading and plant height together explain up to 68% of grain yield (GY) variation, and these associations were further confirmed in several locations across West and Central Asia. Days to heading can be slightly reduced below that of check line Karahan to further improve GY while avoiding the effect of late frosts. Plant height has been decreased in recent germplasm, but further reductions below that of check line Karahan could still improve GY in a wide range of environments. However, in Iranian sites, taller genotypes showed better adaptation with higher biomass and increased reserves for grain filling. Canopy temperature and rate senescence were not associated with GY. A normalized difference vegetation index, used to estimate biomass (Feekes stages 4-5), had intermediate heritability across environments and correlated positively with GY under low plant density and should be explored further as a tool for early selection.

Italian Ryegrass (Lolium perenne) Control and Winter Wheat Response to POST Herbicides

Field studies were conducted to evaluate Italian ryegrass control and winter wheat tolerance to applications of diclofop, mesosulfuron plus methylated seed oil (MSO) alone or with 30% urea ammonium nitrate (UAN), mesosulfuron plus thifensulfuron plus tribenuron plus MSO, mesosulfuron plus MCPA plus MSO, or flufenacet plus metribuzin. Treatments were applied to wheat PRE, two- to three-leaf wheat (2–3 LF) at Feekes stage 1.0 or to one- to two-tiller wheat (TILL) at Feekes stage 3.0, depending on label recommendations. Studies were conducted in Williamson, GA, and Plains, GA, from autumn 2003 to spring 2005. Italian ryegrass control was variable, depending on location and year. Maximum and most-consistent Italian ryegrass control (> 90%) occurred with mesosulfuron plus MSO and UAN. Without UAN, control of Italian ryegrass with mesosulfuron varied from 44 to 97%. That variability was partially attributed to unfavorable environmental conditions associated with cold night time temperatures at or below 0 C, following applications. Wheat injury observed in response to herbicide treatments was minimal (< 15%) and transient; wheat recovered with no differences in yield.

Waterlogging and Hypoxia have Permanent Effects on Wheat Root Growth and Respiration

AbstractWaterlogging causes long‐lasting damage to wheat (Triticum aestivum). Root growth and respiration were investigated after heading in waterlogged, pot‐grown, wheat plants and also in hydroponically grown, wheat seedlings exposed to a hypoxic treatment. In the pot experiment, plants were subjected to 8 days of waterlogging after heading. This period of waterlogging resulted in reduced shoot and root growth through to maturity. The root CO2 emission rates of previously waterlogged and well‐drained plants were about 220 and 140 nmol g−1 per s, respectively, with the rate differences persisting from 10 days after anthesis through to maturity. In the hydroponic experiments, seedlings (Feekes stage 2.0) were exposed to root‐zone, hypoxic treatment for 10–19 days. The roots showed 27 % higher CO2 emission rates and 37 % higher O2 consumption rates, compared with untreated roots. In whole root systems, the high respiration rates found during hypoxic treatment disappeared during recovery under aerated conditions as a result of the appearance of newly initiated roots. However, measurements of the respiration of the previously hypoxic roots showed abnormally high respiration rates. In roots exposed to hypoxic treatment, total sugar concentrations were 3.6‐times higher than in untreated roots indicating that this elevation of sugar may be responsible for the continued high respiration rate. This study shows that roots exposed to waterlogging or to hypoxic treatments do not increase their weights and thus recover from the metabolic disturbances resulting from these treatments.

Winter Wheat Yield Response to a Urea Amended with a Urease Inhibitor and Fertilization Time

Amending urea with a urease inhibitor may be of benefit in reducing NH losses and increasing winter wheat (Triticum aestivum L.) grain yield. Our primary objective was to evaluate wheat yield as affected by urea amended with and without the urease inhibitor Agrotain applied at four different times at a suboptimal N rate. A secondary objective was to evaluate wheat yield response to N rate across four N application times. Six trials were established on silt loam soils in eastern Arkansas with 75 lb N/acre as urea and Agrotain-treated urea applied from mid-February through early April. Five trials also included 125 lb N/acre as Agrotain-treated urea to evaluate wheat yield response to N fertilization rate and time. Averaged across 24 N applications, wheat fertilized with Agrotain-treated urea produced yields that were 3% greater than urea alone. Categorizing the N source yield differences for each fertilization event showed that Agrotain-treated urea increased wheat grain yields by 0%, 6.9%, 10.3%, and 27.1% above that of wheat fertilized with urea for 14, 5, 3, and 2 of the 24 fertilization events, respectively.. Wheat receiving 125 lb N/acre produced yields that were 7% to 15% greater than wheat receiving 75 lb N/acre at four of five sites. Wheat yield response to N application time depended on site-year and suggested that N should be applied before Feekes stage 6.

Effect of selenium fertilizer source and rate on grain yield and selenium and cadmium concentration of durum wheat

Field studies were conducted for 3 yr at two locations in Manitoba, Canada, to evaluate the effect of various sources and rates of Se fertilizer on crop growth and the Se and Cd concentrations of durum wheat. Selenium concentration in durum wheat grown without Se application ranged from 195 to 532 µg kg-1 over the 6 site-years. Selenium seed coating, “Selcote” commercial granular fertilizer, and a foliar spray of sodium selenate solution applied at Feekes stage 5 all increased Se concentration in durum wheat grain at all locations, without negative effects on crop stand, biomass yield or grain yield. Regardless of treatment, Cd concentration in the grain was generally below proposed regulatory limits. Application of Se did not reduce Cd concentration in the grain, regardless of Se source. Selenium fertilization can be used to increase Se concentration of durum wheat, but is not an effective means of reducing the grain Cd concentration. Key words: Selcote, sodium selenate, seed-coating, selenium, cadmium

Foliar Nitrogen Application Timing Influence on Grain Yield and Protein Concentration of Hard Red Winter and Spring Wheat

Foliar N applications on wheat (Triticum aestivum L.) have increased grain protein. Foliar N timing evaluations have been minimal. The objectives were (i) determine the optimal timing of foliar N for increased grain protein of hard red winter wheat (HRWW) and spring wheat (HRSW), (ii) evaluate effect of foliar N on grain yield, and (iii) determine relationship of grain protein to foliar N application and grain yield. Foliar N was applied at Feekes stage 10.0 (boot) or 10.8 (postpollination) on two cultivars of HRWW and HRSW each year from 1995 to 2000. The foliar N rate (33.7 kg N ha−1) was applied as 1:1 solution of urea ammonium nitrate (UAN) and water. Fertilizer N for a 3360 kg ha−1 grain yield goal was broadcast as UAN after planting. Soil type was Estelline silt loam (fine‐silty over sandy or sandy‐skeletal, mixed, superactive, frigid Calcic Hapludoll). Postpollination foliar N gave the highest grain protein during all years. Grain yield was significantly reduced 5% by boot stage foliar N for HRSW. Neither timing application significantly reduced HRWW grain yield. All wheat data were pooled to relate grain yield level and protein response to foliar N. Grain protein and yield from plots without foliar N were inversely related (r2 = 0.57). Postpollination foliar N increased protein 70% of the time when yield goal was exceeded compared with only 23% when it was not. These results show that postpollination foliar N gave higher grain protein and was most effective when planned yield goal was exceeded.

Foliar Nitrogen Application Timing Influence on Grain Yield and Protein Concentration of Hard Red Winter and Spring Wheat

Foliar N applications on wheat (Triticum aestivum L.) have increased grain protein. Foliar N timing evaluations have been minimal. The objectives were (i) determine the optimal timing of foliar N for increased grain protein of hard red winter wheat (HRWW) and spring wheat (HRSW), (ii) evaluate effect of foliar N on grain yield, and (iii) determine relationship of grain protein to foliar N application and grain yield. Foliar N was applied at Feekes stage 10.0 (boot) or 10.8 (postpollination) on two cultivars of HRWW and HRSW each year from 1995 to 2000. The foliar N rate (33.7 kg N ha−1) was applied as 1:1 solution of urea ammonium nitrate (UAN) and water. Fertilizer N for a 3360 kg ha−1 grain yield goal was broadcast as UAN after planting. Soil type was Estelline silt loam (fine-silty over sandy or sandy-skeletal, mixed, superactive, frigid Calcic Hapludoll). Postpollination foliar N gave the highest grain protein during all years. Grain yield was significantly reduced 5% by boot stage foliar N for HRSW. Neither timing application significantly reduced HRWW grain yield. All wheat data were pooled to relate grain yield level and protein response to foliar N. Grain protein and yield from plots without foliar N were inversely related (r2 = 0.57). Postpollination foliar N increased protein 70% of the time when yield goal was exceeded compared with only 23% when it was not. These results show that postpollination foliar N gave higher grain protein and was most effective when planned yield goal was exceeded.

Relationship of nitrogen management to winter wheat yield and grain protein in South Dakota

The effects of nitrogen (N) management systems on Rose and Arapahoe hard red winter wheat (Triticum aestivum L. Emend. Thell.) were measured. Nitrogen fertilizer rates of 0,55,110, and 165 kg N ha‐1 were surface broadcast as a full N rate application atpreplant or were split‐applied as two half N rates applied in the fall and spring. Supplemental N was also applied as a foliar spray treatment after anthesis at either 0 kg N ha‐1 or 33 kg N ha‐1 as a diluted urea‐ammonium nitrate solution. The grain yield of Arapahoe was generally higher than Rose across treatments, but protein was slightly lower. Splitting the N application lowered yield somewhat in both varieties compared to the entire N rate applied at preplant, but grain protein increased by nearly 0.8% with the split application over the preplant application. Grain protein also increased up to 1.6% with a late season foliar N application despite some leaf damage compared to no foliar N. Grain yield was correlated to many agronomic parameters measured throughout the growing season, but grain protein was correlated only to shoot N concentration in samples harvested at the soft dough stage (Feekes stage 11.2).

Quantitative Relationship Between Leaf Rust and Wheat Yield in Mississippi.

Yield losses in wheat (Triticum aestivum) caused by leaf rust were evaluated in cultivar trials at five locations in Mississippi over a 4-year period from 1986 through 1989. Different levels of disease developed in the various trials over the 4-year period. There was no significant interaction between location and cultivar when yield data were collected from sites in the north and central areas of the state. A model derived from data for eight cultivars at two locations showed a negative linear relationship between yield and leaf rust. Total grain yield was reduced by 1% for each 1% increase in rust when the percentage flag leaf area covered by pustules was assessed visually at Feekes stage 11.1. Using this model, and rust ratings from three additional locations, predicted yields were statistically similar to recorded yields.

Prophylactic Control of Aphids in Spring Wheat, Crookston, Mn, 1994

Abstract Plots 25 ft X 50 ft were established in bulk wheat at the Northwest Experiment Station. The wheat was planted on 18 May and chemical applications were applied at tillering (Feekes stage 3), flag leaf (Feekes stage 8) and at late milk (Feekes stage 11.1). Insecticides and fungicides were mixed separately and applied individually. Treatments were arranged in a RCB design. Two treatments with neither insecticide nor fungicide resulted because aphid numbers did not reach our present action level of 85% of stems with one or more aphids per stem. The total volume of material applied per acre was 40 gallons. Aphid populations were sampled at early dough by collecting 20 heads, placing them into alcohol, and counting aphids at a later date. Yields were collected using a small grain plot combine and harvesting a 5 ft swath 50 ft in length. The grain was dried and moisture adjustment made for final tabulated yields.