Effect of root growth characteristics on nitrogen use efficiency of tropical maize (Zea mays L.) varieties.
1995
Heuberger H.T. | Kling J.G. | Horst W.J.
In the cultivation of maize under high rainfall conditions in the lowland wet tropics, nitrogen is the most limiting nutrient. Considerable work has been undertaken to improve nitrogen use efficiency of maize through crop management and breeding. Yet, little is known about the effect of root characteristics on N use efficiency. Plants with a deeper root system at an early stage of development may be better able to capture the first flush of mineralized N, which is readily leached down from the top soil. In a field study, 11 varieties of tropical maize were grown under 3 rates of nitrogen fertilizer (0, 30 and 90 kg N ha-1) on a deep Alfisol in the South Nigerian forest zone. Root length densities (RLD) were determined 32 days after planting (DAP) down to a maximum rooting depth of 60 cm. In addition, plant dry matter, N uptake, and grain yield were determined. Varietal differences in dry matter, N concentration and N uptake 32 DAP and at silking, and grain yield were detected. Dry matter accumulation and N uptake at silking were related to grain yield. Under low N, yield was correlated with N uptake and dry matter production early in crop growth. Due to high variation in root data, it was not possible to detect differences in RLD at each depth, although some trends were visible. We could not generalize that varieties with larger root systems take up more nitrogen. When screening seedling root growth in pots, varieties differed in root length and in their ability to penetrate a wax layer in the soil. These traits were not correlated with each other nor with root growth in the field. Experimental modifications to reduce variability of root data and to obtain a closer relationship between root growth in the field and in pots are suggested.
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