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Agronomy Journal Abstract -

Yield and Quality of a Warm-Season Grass Mixture Treated with N, P, and Atrazine1


This article in AJ

  1. Vol. 76 No. 5, p. 731-734
    Received: Sept 1, 1983

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  1. G. W. Rehm2



Warm-season grasses can be important in pasture systems in the eastern Great Plains. Currently, production from the majority of pastures which contain these grasses is quite low and improvement is needed. In previous research with warm-season prairie grasses, the effect of fertilization as well as the influence of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] has been investigatd in separate studies. Only limited research has been conducted to evaluate the combined effects. This study evaluated the rate and frequency of fertilizer N and P with and without use of atrazine on yield and protein content of warm-season prairie grasses. Three management systems (annual fertilizer with no atrazine, annual fertilizer with atrazine, biennial fertilizer with atrazine) were randomized and replicated in the experimental area. The soil was a Crofton silt loam [fine-silty, mixed (calcareous) mesic Typic Ustorthent]. Applications of N (0, 34, 67, 101, and 134 kg ha−1) and P (0, 6, 12, 18, and 24 kg ha−1) were applied to the systems involving annual fertilization. These rates were doubled when applied on alternate years (1974, 1976, 1978). Atrazine (1.12 kg ha−1) was applied in early April in 1974, 1976, and 1978. All fertilizer treatments were applied in late May. The response to P was linear in all situations. The response to N was linear where atrazine was not used and curvilinear where atrazine was applied. Atrazine effectively controlled weeds and encroachment of cool-season species. Compared to the system where no herbicide was used, atrazine applied every 2 years resulted in higher forage production in 4 out of 6 years. Crude protein concentration of the forage increased by about 35 g kg−1 with the use of fertilizer N. Neither applied P nor atrazine affected crude protein concentration.

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