Demand-Driven Technologies for Sustainable Maize ... - IITA

184ha -1 . Fields were planted on June 27 in 2002 and July 5 in 2003. Atplanting, P in the form of single superphosphate and K as muriate ofpotash were applied at the rate of 40 kg ha -1 each. N in the form ofcalcium ammonium nitrate was applied in two equal splits. One halfwas applied one week after planting (WAP) and the other half at 5WAP. Weeds were controlled manually at 2 and 5 WAP and by usingparaquat (1:1-dimethly-4,4’-bipyridinium dichloride) at 7 WAP.GenotypesThree drought-tolerant (Menkir et al. 2001; Kamara et al. 2003),fi ve low-N tolerant (J. Kling, personal communication), two hybridsand four adapted or Striga tolerant, late maturing open-pollinatedvarieties (OPV) developed at IITA, were evaluated in this study (Table2). One of the OPVs (ACROSS 8328 C7 BN) was developed at theInternational Center for Maize and Wheat Improvement (CIMMYT)using recurrent selection procedures. One of the hybrids (Oba Super2) has been found to be N-effi cient (Sanginga et al. 2003) while oneof the OPVs (TZB-SR), though widely grown in the Guinea savanna ofWest Africa, is N-ineffi cient.Data collectionData were collected from the two central rows leaving the outsiderows and the plants at the beginning and end of each row to serveas borders. Days to 50% pollen shed (anthesis date) and 50% silkextrusion (silking date) were recorded and the anthesis-silking interval(ASI) was calculated as the difference in days between 50% silking and50% anthesis. Plant and ear heights were determined approximatelytwo weeks after anthesis.Stay-green scores were recorded in the N-defi cient plots on a scaleof 1 to 9; where 1 = almost all leaves below the ear were greenand 9 = virtually all leaves below the ear were dead. Grain yield wasrecorded for 26 plants harvested from the two central rows of eachplot (4.7 m 2 ), excluding the end plants of each row. The total numberof plants and ears were counted in each plot at the time of harvest.The number of ears/plant was then calculated as the total numberof ears at harvest divided by the total number of plants harvested.Ears harvested from each plot were shelled and the percentage grainmoisture was determined using a Dickey-John moisture tester (Model14998, Dickey-John Corporation, Auburn, USA). Grain yield adjustedto 12% moisture was computed from the shelled grain.Data analysisThe General Linear Model procedure (GLM) of the Statistical AnalysisSystems (SAS) Package (SAS Institute Inc. 1990) was used to analyzethe data and signifi cant differences among varieties were compared