J. .\pw>oiny & Crop Science 177, 207—215 (19%) ©1996 BbckweD WTissenschafts-Veriag, Betin ISSN 0931-2250 f.ftjo PndiKtim Pnffamat, .4bubakar T4aa» Balema Ummsity, PMB 0248, Bmtdn, Response of Rainfed Sunflower {HeUatahus anntms L.) to Nitrogen Rates and Plant Population in the Semi-arid Savanna Region of Nigeria V. A. TENKBK, U. R. PAL, C. A. C. OKONKTCO and B. M. AtWALt: Authors" address: Dr V. A. TrKfiBR, Prof. U. R. P.U, Dr C. A C OKtiNKWO and Dr B. M. A|-KAU:. SchiKd of e. Abubakar Tafawa Balewa Universit\-, PMB 0248. Bauchi, Nigeria [ Tith 4 tebks ami 2 f^rts Ktaivei Manb 4. f996; acaptedJiar 17, 1996 Abstract Field expenments were conducted during die wet sea.«ms of 1991,1992 and 1993 at the Abubakar Tafawa Bale»a University' Faim, Bauchi (10 " 22 "N, 09 "47 'E) to study the response of sunflower {HibaHthm animus L.) to N rates and plant populaUon under rainfed condirions. Four N rates (0, 50, KM) and 150kgN ha ') and fout planr popuiatKms (40000,80 000,120 000 and 160(KX> plants ha ') were facroriaJly combined in a randomized complete block design widi three replications. Leaf area index, shoot diy weight and seed yiekl (kgha"') mcteased significantly with increasing N rates fnimOtoiOOkgNha"'. The grtwth and weld parameters per plant decrea.scd significantly widi increasing plant populations from 40 000 to 160 00(1 plants ha" , but rhe seed VKAA (kji; ha ) ' obtained at KOfKKl plants hi ' wa.<; sipnificandy higher than all the other plant populations. The interactions of K X plant pi^ularion confounded the njain effect of each factor on the growth and >Held of sunflower. The seed lidd (3425 kg ha"') obtained from the use of 100 kg N ha"' at 80 (MK> pbnts ha ' was stj?nilicandy higher thai thtw obtained from all other combinanons of N >: population and out-yielded die main effects of HjO kg N ha and BO 00ft plants ha"' by 18 % and 25 %, tespecrively. The use of 100 kf> N ba"' at HO O(XI plants ha is therefirte tccnmmencied for maximum viekJ of sunflower in Bauchi. Introduction ainnost completely lacking for tbe northern Guinea savanna region of Nigeria. Recommenda- The semi-arid northern Guinea savanna regjon of tions on fertilizer N firom other parts of the Nigeria is characterized by soils wbich are mainly world are cotitradictorv'. t>ptiinum rates of N sandy to sand>' loam, chacacterisdcaffly low in N applicadon for maximum yields were reported to and Carbon (SiNtjn 1986). TTie annual rainfaU differ wids m^Ttonments with figures tanging onges f^om 800 to 1000mm mosdy distributed fiom 30 kgN ha (CHAUDHARY and PATI'RDE between the montbs of May and'September. 1981) to 120kgN ha (VIVTK and CHAKOR Consequendy. apart frcan groundnuts, the major 1992). The effect of plant population on die <Mt crops of economic importance in Nigeria arc field performance of sunflower bas also been the lurt adapted to the northern Guinea savanna. On subject of several investigations (MASSKV 1971 fhe otiier band, there is ample evidence tbai this NARWAL and MAUK 1986, KHAROAKHARATK and vast agro-ecokgical complex is suitable for NlR«ou. 1993). Various optimum population senflower production (ADO and TANIMU 1987, levels have been reported for various agro- Tf^HBE and UMARU 1989, TANJMU et al. 1991). ecok^cal zones (ZuBwaa and ZIMMERMAN However, a predse agronomic package for the 1974, BiNtJKA and KHAKW.MW 1992). SimUarly, ptoducdon of this vital higb quality oil crop is results obtained by different workers for die * '^ t^owngb, a « » « c««r Code s«o««t 0931-2250/96/770.3-0207|l 1.50/0