Abstract

FRIGERIO, K.L et al. Curva de dilución e índice de nutrición nitrogenada para Digitaria eriantha cv. Irene bajo diferentes regímenes de agua y nitrógeno. RIA. Rev. investig. agropecu. [online]. 2016, vol.42, n.2, pp.175-185. ISSN 1669-2314.

The main environmental factors that influence the productivity of pastures are the water condition and the availability of nitrogen in the soil. Temperature is also cause seasonal fluctuation in biomass production. In Digitaria there are insufficient studies that relate dynamics of nutrition with N under different levels of nitrogen fertilization and soil water condition. It is proposed to obtain the curve of theoretical and experimental nitrogen dilution; estimating the nitrogen nutrition index (INN) and to evaluate the degrees relative to days of growth (GDC), for two cycles of growth Digitaria eriantha cv. Irene subject to natural and potential conditions contribution to water and nitrogen in spring and summer. Two soil moisture levels were evaluated: natural condition (CN) and field capacity (CC) between November 2007 and February 2009.Two levels of N input were applied in CN 0 (CN0) y 150 kg.ha-1 (CN150), and three levels of N input were applied en CC 0 (CC0), 150 (CC150) y 300 kg.ha-1 (CC300).Dilution curve, critical and theoretical N concentration, nitrogen nutrition index were obtained. Also, nitrogen accumulation curves related to growing degree days. The input of nitrogen to the soil increased the N concentration in biomass in both cycles and for the two seasons evaluated. In both seasons curves with lower N inputs (CN0 and CC0) were those that produced less biomass, even with sufficient water availability. However, with adequate supply of N, water becomes the limiting factor (CN150). Lower values of INN were obtained in the treatments without any application of N. The accumulation of nitrogen increased with increasing degree days in spring and summer. The maximum value of accumulation is reached around 500 GDC, regardless of treatment. For this species and the environmental conditions described, adequate levels of accumulation of nitrogen in plant dependent on the availability of N in the soil. The availability of N for the plant has more effect when there is water available in the soil. The combination of both factors synergizes their individual effects. In both seasons accumulation values were reached sufficient temperature for the plant to obtain an adequate level of nitrogen, subject to the availability of N and soil moisture effect.

Keywords : Growing season; C4 grasses; Water condition; Nitrogen fertilization.

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