NUTRIENT AND STRUCTURAL CARBOHYDRATE PARTITIONING IN PEARL-MILLET

Cereal stovers and other crop residues are vital feeds for ruminants during the 6- to 8-mo dry season in mixed farming systems of semiarid West Africa. Reducing the competition between livestock and soil fertility is crucial to the sustained productivity of these farming systems. A 2-yr field study was conducted in Niger on a sandy siliceous isohyperthermic Psammentic Paleustalf to determine the effects of fertilizer N (15 and 45 kg ha-1) and P (4.4 and 17.4 kg ba-1) on dry matter (DM), N, P, and structural carbohydrate distribution in plant parts of pearl millet [Pennisetum glaucum (L.) R. Br.]. Fertilizer N increased total millet DM by 13%, N uptake by 63%, and P uptake by 29%. Fertilizer P increased total millet DM by 100%, N uptake by 80%, and P uptake by 140%. Fertilizer N increased millet grain yield only during the year of adequate rainfall, whereas fertilizer P increased yields during both years. Fertilizer N increased and fertilizer P decreased the N concentrations in millet stover. Fertilizer P increased the P concentrations in all upper plant parts. The average total millet DM of 2.75 Mg ha-1 was partitioned into grain (18%); animal feed consisting of chaff, immature panicles, upper stover and tillers (41%); and middle and lower stover components for soil conservation (41%). Partitioning was not affected by fertilizer addition. Of the total N (33.4 kg ha-1) and P (5.2 kg ha-1) uptake, 32 and 40% were contained in grain, 41 and 40% in animal feed, and 27 and 20% in components for soil conservation. Results of our study show the importance of N and especially P in increasing grain and forage yield and quality, and that stover can be managed more effectively to raise both crops and livestock in a more sustainable manner.