Information on nitrogen (N) fertilization of no‐till (NT) cotton (Gossypium hirsutum L.) is needed to optimize lint yields and earliness. We evaluated five N rates and three application methods for NT cotton production on Loring silt loam (fine‐silty, mixed, active, thermic Oxyaquic Fragiudalfs) with natural winter annuals as a cover; and on Memphis silt loam (fine‐silty, mixed, active, thermic Typic Hapludalfs) having corn (Zea mays L.) stover as a cover and on Lexington silt loam (fine‐silty, mixed, active, thermic Utlic Hapludalfs) having winter wheat (Triticum aestivum L.) as a cover. Nitrogen rates of 0, 34, 67, 101, and 134 kg ha−1 were either broadcasted as ammonium nitrate (AN) or injected as urea–ammonium nitrate (UAN) at planting. Additional treatments included broadcasting 67 kg N ha−1 as AN at planting with either 34 or 67 kg N ha−1 banded 6 wk later. Relative to no N, broadcasting 67 kg N ha−1 as AN increased 4‐yr average NT lint yields on Loring silt loam from 739 to 1281 kg lint ha−1 and 2‐yr average yields on Lexington silt loam from 1086 to 1535 kg ha−1. A higher N rate (101 kg N ha−1) was needed to increase 2‐yr average yields on Memphis silt loam from 821 to 1169 kg ha−1. Broadcasting AN was a satisfactory placement method producing yields equal to or higher than injecting UAN or splitting AN for NT cotton produced on these loessial soils despite different covers and residues.

Spring N applications increase wheat (Triticum aestivum L.) grain yields in the Mid‐South. The interactive effect of increased N rates and foliar fungicide applications on the common Mid‐South winter wheat foliar diseases—leaf blotch (Septoria tritici Rob. in Desm.), glume blotch and leaf spot [S. nodorum (Berk.) Berk.], and leaf rust (Puccinia recondita Rob. ex Desm. f. sp. tritici)—is not clearly understood. Research was initiated in 1984 on a Collins silt loam soil (coarse‐silty, mixed, acid, thermic Aquic Udifluvents) and continued each year through 1987 to evaluate the effect of N rates and fungicide applications on disease severity in wheat. Spring N rates of 0, 30, 45, 60, 90, and 120 lb/acre were applied at Feekes' growth stage (GS) 3. Fungicides were applied twice during the spring at GS 8 to 9 and GS 10.1 to 10.5. The research was continued between 1988 and 1990 on a Loring silt loam soil (fine‐silty, mixed, thermic Typic Fragiudalfs), but with a reduced number of N treatments. Experimental sites were changed each year on these two soils. The effects of N rates and fungicide applications to wheat were evaluated through grain yields, kernel weights, test weights, and estimated percentage plant foliage and heads infected by diseases. The applied N rates did not have the same effect on increasing yields during the years of the experiment. Generally, yields were increased to a level and then decreased with higher N rates. Fungicide applications had a greater effect on yields produced at the higher N rates. Severity of diseases differed with year, N rate, and fungicides. The severity of the three diseases was increased with N rate, especially when fungicides were not applied, but fungicides reduced disease severity. Yield reductions could not be attributed to any single disease but to a combination of diseases, and reductions could not be ascertained from kernel weights or test weights. Research Question Throughout the Mid‐South, wheat yields may be reduced by one or more plant diseases that may incraese with incraesed N fertilization. This study evaluates spring N and foliar fungicide effects on grain components and disease severity of wheat. Literature Summary Diseases have had a negative but inconsistent effect on grain yields. Not only is severity inconsistent with years, but the predominate disease may differ. In this region, one or more diseases may affect wheat during the growing season. High N rates tend to increase infection by increasing plant susceptibility to these diseases. The disease severity increases with applied N when fungicides are not applied. Study Description Spring N rates and fungicides were applied over 7 yr, evaluating their effect on wheat. Experiment Design: Main‐plots, spring N rates of 0, 30, 45, 60, 90, and 120 lb/acre plus a split N rate (45 lb applied at Feekes’ GS 3 + 45 lb applied 3 to 4 wk later) were applied to a Collins silt loam soil for 1984 through 1987. Main plot N rates plus the split‐rate were applied to a Loring silt loam soil. Sub‐plots, fungicides, Bayleton p...

Continuous no‐till production of cotton may result in vertical stratification of nutrients similar to that observed for band fertilizer applications. If so, special soil sampling techniques may be required to adequately address the fertility status of no‐till soils. The objective of this study was to evaluate nutrient stratification relative to the planted row and with soil depth on three soils having broadcast K at various rates applied annually for 6 years to no‐till cotton (Gossypium hirsutum L.). Rows were planted within a few centimeters of the rows from the previous year; a common practice in no‐till agriculture. The selected soils were Memphis silt loam (fine‐silty, mixed, active, thermic Typic Hapludalf), Lexington silt loam (fine‐silty, mixed, thermic Ultic Hapludalf), and Loring silt loam (fine‐silty, mixed, active, thermic Oxyaquic Fragiudalf). Potassium rates of 0, 28, 56, and 112 kg ha−1 were broadcast annually beginning in 1991. Experimental design was a split plot with five replications. Samples were collected from individual plots in the planted row (IR) and between the row (BR) to a depth of 30 cm. The soil samples were divided into 0‐ to 8‐cm, 8‐ to 15‐cm, and 15‐ to 30‐cm depths and Mehlich‐1 P and K were evaluated. Mehlich‐1 P varied with soil, sampling position, and soil depth. Differences in extractable P levels due to sampling position would not affect soil test ratings; however, additional years in no‐till production may magnify position influences and so affect P fertilizer recommendations. Mehlich‐1 K was greater for the IR sampling position of the 0‐ to 8‐cm sampling depth for the three soils. Sampling only the BR position may in some instances give a lower soil test value, resulting in higher fertilizer applications. These differences varied with soil‐applied K rates and may increase with additional time in no‐till cotton.

Shortterm, splitroot experiments were conducted with cot ton seedlings (Gossypium hirsutum) in which the upper por tion of the root medium was a sandy loam surface soil and the lower portion was either a nutrient solution or a subsoil material at various Ca levels. The Ca required in subsurface media for penetration was dependent upon the Ca/totalcation ratio rather than the Ca concentration per se. The Ca require ment was apparently the same in soil solutions in situ as in nutrient solutions, namely, between Ca/totalcation ratios of 0.10 and 0.15 in all cases. Critical levels of exchangeable Ca were equal in Norfolk and Dickson subsoils when Ca was expressed as a ratio of Ca to total exchangeable cations even though the clay fraction of Norfolk is kaolinite while the clay fraction of Dickson is vermiculite with some montmoril lonite. Norfolk subsoil at pH 5.0 and Dickson subsoil at pH 4.6, as obtained from the field, contained adequate Ca for nor mal growth of primary cotton roots.

Rotations have long been used to improve crop yields. No‐tillage production acreage is increasing, and production information on rotation effects on yields and soybean cyst nematode populations is needed for this system. Field experiments were initiated in 1985 and continued through 1992 to evaluate P‐K fertilization effects on yield of a corn‐soybean [Zea mays L.‐Glycine max (L.) Merr.] rotation and on populations of soybean cyst nematode (Heterodera glycines Ichinohe) (SCN). The research was conducted on a Loring silt loam soil (a fine‐silty, mixed, active, thermic Oxyaquic Fragiudalf), using no‐tillage management. The experimental design was a split‐plot for corn evaluation and split‐split‐plot for soybean evaluation. Individual treatments were replicated five times. Main plots were broadcast P‐K rates of 0–0, 15–28, 29–56, 44–84, and 59–112 kg ha−1. The split‐plots were continuous corn, continuous soybean, a corn‐soybean rotation, and a soybean‐corn rotation. The split‐split‐plots were two soybean cultivars possessing different levels of SCN resistance. Yields of both crops were increased by the fertilization. In this study, corn yields were increased 14% and soybean yields increased 11% with the rotation. Rotating the two cultivars produced similar yields and nonrotated yields of resistant TN 4‐86 were higher than susceptible Essex, indicating an effect of SCN. The primary benefit of corn in the rotation was to reduce SCN populations. However, within Essex rotations the SCN population recovery was rapid, while populations remained relatively low in the TN 4‐86 rotations. The SCN populations were greater when rotations were fertilized with the two lowest P‐K rates, compared with populations within the unfertilized check and the highest P‐K rate. Soybean producers should consider a no‐tillage system of rotating corn with SCN‐resistant soybean cultivars, fertilized at high P and K rates for yield improvement and reduced SCN populations.

Earliness of maturity is essential for adaptation of cotton (Gossypium hirsutum L.) to regions with short growing seasons, and it may be influenced by potassium nutrition. Our objectives were to determine effects of K fertilization on interception of photosynthetically active radiation and earliness, and to describe the relationship between earliness and light interception at different in‐canopy heights. Research was conducted with no tillage on a Memphis silt loam (fine‐silty, mixed, active, thermic Typic Hapludalf) with low extractable K. Using a split‐plot randomized complete block design, 0 and 112 kg K ha−1 were soil‐applied before planting each year as mainplot treatments, and 0 and 4.1 kg K ha−1 were foliar applied four times per season as subplot treatments. Canopy interception of photosynthetic photon flux density (PPFD) was measured at 23‐cm vertical increments in 1993 and 1994. Plots were spindle‐picked twice each year. Earliness was measured as the percent of total yield picked at first harvest. Relative to no fertilizer K, soil‐applied K increased canopy PPFD interception at all heights measured. Neither soil‐applied nor foliar K affected earliness in 1993, a drought year, but soil‐applied K decreased percent first harvest from 78 to 65% in 1994. Foliar K did not affect canopy light interception in 1993, and it increased interception in 1994 only with no soil‐applied K. At 111 d after planting, percent first harvest was negatively correlated with PPFD interception at all measured heights in the canopy, suggesting that higher K fertility delayed maturity as it increased upper‐canopy light interception. In short‐season environments, optimum K fertilization needs to be accompanied by cultivar selection and management that promote earliness of maturity.

Surface applying urea‐containing N fertilizers may result in greater N losses by volatilization of NH3 as urea hydrolyses than nonurea containing materials. The objective of this study was to evaluate the N efficiency of urea‐ammonium nitrate (UAN), urea and urea‐urea phosphate (UUP) at 56, 112, 168, and 224 kg ha−1 N rates applied broadcast, surface banded, and injected for no‐till corn (Zea mays L.). Yield, ear‐leaf N concentration, and N uptake were used to estimate N availability. Broadcast ammonium nitrate (AN) and injected anhydrous ammonia (AA) were used as controls for evaluating N efficiency of urea‐containing N sources and their application methods. The method of applying the urea‐containing N sources has a significant effect on apparent N fertilizer availability. Injecting UAN and urea resulted in significantly higher yield, leaf N concentration, and N uptake when compared with broadcast and surface band application methods. Surface banding UAN at 168 and 224 kg ha−1 resulted in higher yields than urea or UUP. Yield, leaf N concentration and N uptake differences among the three urea‐containing N sources were not observed when broadcast applied. Broadcasting AN at 168 and 224 kg ha−1 resulted in higher yields than UAN, urea or UUP. Injecting the N sources resulted in higher yields when compared with broadcasting AN.

on soils having Mehlich-1 extractable K of 177 kg ha Ϫ1 or less. Yield response to foliar K continued through Foliar applications of K may be used to supplement soil applications two years of soil-applied 112 kg K ha Ϫ1 plus two years to maximize yields of cotton (Gossypium hirsutum L.). Response to foliar K applications may be improved by choice of K source, buffering of foliar-applied K (four applications per year at 4.1 kg the spray solution, or applying K with B. Research was conducted ha Ϫ1 each). Oosterhuis (1993) indicated that responses on a Collins silt loam (coarse-silty, mixed, acid, thermic Aquic Udifluto foliar K can probably be expected when Mehlich-3 vents) and on a Memphis silt loam (fine-silty, mixed, active, thermic soil K level is 308 kg K ha Ϫ1 or lower. This extractable Typic Hapludalfs) to evaluate KNO 3 , K 2 SO 4 , K 2 S 2 O 3 , and KCl as K K level is similar to the 177 level reported above, using sources. A second study evaluated foliar KNO 3 and K 2 SO 4 solutions Mehlich-1 extractant, since Mehlich 3 extracts approxiapplied unbuffered and buffered to pH 6 and 4 on cotton K nutrition mately 1.5 times more K than Mehlich 1 (H.G. Savoy, and yield. Foliar K in both studies was applied at 4.1 kg K ha Ϫ1 per personal communication, 1998). Tillage system may also application. A third study evaluated combinations of soil-applied and contribute to the response to K fertilization. Howard foliar-applied B and K. Foliar treatments were applied in 93.5 L ha Ϫ1 et al. (1997) reported that no-tillage cotton yields were water at early flower or 2 wk after and repeated on a 9-to 14-d interval between the four applications. Yields from the four K sources increased by applying K to a soil having 225 kg Mehaveraged 10% higher than the untreated check and yields with KNO 3 lich-1 extractable K ha Ϫ1 , but conventional-till yields were 4% higher than the other K sources. Buffering two K source were not increased by applying K to a soil having 193 solutions to pH 4 resulted in 10% higher yields than the check or kg extractable K ha Ϫ1. unbuffered K solutions. Adding a surfactant (ethoxylated alkyl aryl The foliar-applied K source may also affect yield rephosphate esters) to KNO 3 resulted in 5% higher yields then the sponse to foliar fertilization. Miley and Oosterhuis check. Compared with untreated check yields, soil-applied B at 0.56 (1994) summarized three years of evaluating KNO 3 , kg B ha Ϫ1 increased yields by 6%, four foliar applications of 0.11 kg K 2 SO 4 , K 2 S 2 O 3 , KCl, and K 2 CO 3 as foliar K sources and B ha Ϫ1 increased yields by 8%, and four foliar applications of 0.11 reported that KNO 3 increased lint yields, relative to the kg B plus 4.1 kg K ha Ϫ1 increased yields by 13%. Foliar K solution other sources, in two of the three years. Mullins and buffering and/or the inclusion of foliar B are relatively inexpensive ways of improving yield response. Based on yield increases in this Burmester (1995) reported that lint yields were instudy, these treatments should return 8 to 10 times the pr...