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Split fertilizer N application has been proposed for improving N uptake efficiency in wheat (Triticum aestivum L.) production systems, but results have been inconsistent. In this field study, 75 and 150 kg N ha−1 was applied either all preplant or in two, three, or four split applications based on wheat growth stage (GS) to determine N timing effect on wheat yield and apparent fertilizer N recovery. Vegetative samples were also collected at Feekes GS 4, 6, and 10 to determine treatment effects on tissue N concentration during the growing season. Soil samples were collected after harvest to evaluate residual N quantity and movement in soil relative to N rate and time of application. The soil used was a Fluventic Ustochrept‐Udic Chromustert intergrade. Nitrogen rate and application timing appeared to have less effect than year on yield and N parameters. Significant grain yield increases were achieved with split applications of N fertilizer when N was topdressed at GS 4 or 6 in 1989 as compared with all preplant or application at GS 10. Split N application at GS 10 produced greater grain yield than application at GS 4 or 6 in 1990. Nitrogen uptake efficiency was greatest with 75 kg N ha−1 and split application. Soil NO‐3–N concentration was significantly higher at 150 kg N ha−1 than at 75 kg N ha−1. Significantly lower residual NO‐3‐N with the preplant treatment was not accounted for by greater grain or straw N content.

Nitrogen is an important agronomic input for bermudagrass production in the southern USA. Fertilizers that can efficiently provide N to grass pastures and hay meadows are an important issue because of increasing costs and environmental problems associated with N losses. This experiment was designed to determine the effectiveness of various N sources on ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] production and N uptake efficiency. Nitrogen was applied at 0, 45, 90, and 135 kg ha−1 harvest−1 as urea–ammonium nitrate (UAN), urea, ammonium nitrate (AN) and ammonium sulfate (AS) on Gallime (Glossic Paleudalf) and Lilbert (Plinthic Paleudult) soils. Mixtures of S with UAN and of Ca and B with urea were also evaluated. Bermudagrass was periodically harvested and subsampled for total N analysis. At termination of the study soil samples were collected for pH and extractable NO3–N analyses. Bermudagrass yield responses to N sources were significant only in the Gallime soil. In this soil, AN and AS increased yields and resulted in greater N uptake compared to urea and UAN. Lilbert soil showed no effect of N sources on dry matter (DM) production. There was a yield response to N rates and maximum bermudagrass production was generally achieved at the 90 kg ha−1 N rate regrowth−1. Fertilizer efficiency declined as the N rate was increased. Soil acidity increased in response to N application, particularly for the AS treatments. Selection of N sources and rates should be carefully planned to avoid detrimental effects on soil acidity and, consequently, fertilizer efficiency.

Alfalfa (Medicago sativa L.) is a rare forage crop on Coastal Plain soils. Acid soils, wet conditions, and the prevalence of perennial, warm‐season grasses limit alfalfa production. Development of grazing‐tolerant varieties raised interest in growing alfalfa on the Coastal Plain. This three‐year dryland field study was conducted to evaluate coincident production of ‘Alfagraze’ alfalfa and ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] as a sustainable forage system. Limestone (effective calcium carbonate equivalence ECCE 72%) at a rate of 6.1 t ha−1 was incorporated by roto‐tilling 15 cm deep in an established sod of Coastal bermudagrass on a Darco loamy fine sand (loamy, siliceous, thermic Grossarenic Paleudults) in late winter 1990, with an additional 3 t ha−1 surface‐applied in June 1991. Alfalfa was seeded in October 1990 at 23, 46, 69, and 92 cm between rows in main plots of a split‐plot design. Nitrogen rates from 0 to 112 kg ha−1 in increments of 28 kg ha−1 were applied to subplots for every bermudagrass regrowth cycle. Other plant nutrients (including P, K, Mg, S, B, Zn, and Cu) were applied at rates considered adequate for alfalfa on a low‐fertility soil. Yield of alfalfa at the 23‐cm row spacing in 1991 was 8.8 t ha−1 and declined to 6.7 t ha−1 at 69cmtrue(P=0.05true), while yield of bermudagrass increased from 3.2 to 5.7 t ha−1, respectively, at these row spacings. In 1992, alfalfa yield increased an additional 2.2 t ha−1 at each row spacing, with a compensating decline in bermudagrass production. Alfalfa yielded 11 t ha−1 at all row spacings in 1993, despite a midseason drought, while bermudagrass yield was <450 kg ha−1. Row spacing had no effect on total forage production in any year. Higher N rates increased bermudagrass yield the first two years. Applied N increased alfalfa yield at certain harvests, but had no effect on total annual production. Crude protein in alfalfa declined or remained similar as row spacing was widened. Soil pH was lowered by increasing N rates and by narrower alfalfa row spacings. Results indicate that alfalfa competes well with Coastal bermudagrass, even in drought conditions.

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