GRAIN YIELD OF MAIZE VARIETIES OF DIFFERENT MATURITY GROUPS UNDER MARGINAL RAINFALL CONDITIONS

This study was conducted to evaluate the yield performance of different maturity groups of maize varieties at different planting dates under the marginal rainfall conditions of the rainforest ecology of Nigeria and identify the high yielding ones. The maize varieties were evaluated on five and three different planting dates in 2001 and 2005 late cropping seasons respectively. Seven planting dates were used in 2002 and 2006 early cropping seasons. All plantings were done at a weekly interval. Data were obtained on grain yield and yield components. Grain yield and yield components decreased as planting was delayed in the late seasons while in the early seasons they showed contrasting trend. To obtain optimum yield for the maturity classes evaluated, the varieties must be planted about the end of August or first week of September for the late season and about the middle of April in the early season. At the optimum planting date TZEEWSRBC s and ACR 90 POOL16-DT with grain yield of 3.8 tons ha1 and 6.4 tons ha1 were the highest yielding varieties in 2001 and 2002 respectively. In 2005 late cropping season, TZECOMP3DT (1.7 tons/ha) was the highest yielding while in 2006 early cropping seasons, ACR 95 TZECOMP4C3 (4.37 tons/ha) was the highest yielding variety. I n t r o d u c t i o n Maize (Zea mays L.) originated and survived in an area of alternating wet and dry seasons in Mexico, which is universally accepted as its most probable centre of origin. The broad adaptation of maize to all agro-ecological zones in Nigeria is, therefore, not surprising. Maize has become a major food item in Nigeria and it is consumed in many forms. It is consumed as green maize when the ear is boiled or roasted. When dried, the grain may be processed into different forms of products; for example, pap (ogi) and starch. Maize is also fast becoming an industrial crop in Nigeria. 1 Department of Crop Production and Protection, Obafemi Awolowo University, email: boluwaranti@oauife.edu.ng 2 Coordinator, WECAMAN, UTA, P.M.B. 5320, Ibadan 184 A.Oluwaranti et al. Flour mills, feed mills, breweries as well as breakfast cereal and baby food industries all use maize as the primary raw material. Observations by F a k o r e d e and A k i n y e m i j u (2003) at IIe-Ife (7°28'N 4°33'E, 244 m) in the marginal areas of the rainforest ecology of south-western Nigeria suggest that the global climatic change is already impacting maize production practices and yield. According to these authors, rainfall at lIe-Ife has been characterized by false starts, which showed a tendency to be more i ntense in the later than earlier years of the period under study. The combination of reduced rainfall and false starts of the rainy season provides an explanation for a shorter cropping season and increased drought probability in March, April and May observed at this location in recent years. S a k a (1997) inferred from the analysis of climatic data collected at the Teaching and Research Farm (TRF) of Obafemi Awolowo University that effective rainy season begins in May and ends in October at lIe-Ife. He concluded that for maize production to be successful, planting should not be done earlier than the first week of April for the early season planting. As for the late season, planting should starts from the fourth week of July to the second week of August to avoid the effect of drought during the grain filling stage of the late season crop ( S o d i m u 1991). More recently, in the United State of America, initiation of corn planting now averages approximately 2 weeks earlier relative to the early 1980's ( K u c h a r i k 2006). It has however been reported by K u c h a r i k (2008) that early planting of maize allows late maturing varieties to give higher yield in comparison to late planting in the Central United States. Wi l l i a m and L i n d q u i s t (2007) noted that crop planting date and canopy density influence interactions between weeds and sweet corn. They further observed that late planting date resulted in 9% taller crop plants with 36% lower maximum leaf area index (LAI) as a result of weed interference on sweet corn. As noted by F a k o r e d e (1985), high maize yield can be obtained in the rainforest zone if drought-tolerant or drought-escaping varieties are available to the farmers. Through collaborative research involving maize programs in West and Central Africa, the West and Central Africa Collaborative Maize Research Network (WECAMAN), International Institute of Tropical Agriculture (UTA) and the Maize and Wheat Improvement Center (CIMMYT), Mexico developed early maturing maize varieties that produce dry grains in about 90-95 days and extra early varieties that produce dry grains in 80-85 days and could be eaten as fresh maize in about 65 days after planting. Availability of the early and extra-early varieties is a strategy for adapting maize to the gradually shortening rainy season, so that maize could escape the drought stress that occurs during the grain-filling stage in the late season. The early and extra-early varieties were specifically developed for cultivation in the northern fringes of the northern Guinea savanna (NGS) and the Sudan savanna (SS) ( F a j e m i s i n 1989; B a d u A p r a k u and F a k o r e d e 1999; O n y i b e et al. 1999). Although the early and extra-early maize varieties could also increase maize production under the marginal rainfall conditions Maize grain yield under rainfall conditions 185 of the rainforest zones, their performance in this ecology has not been evaluated. This study was thus conducted to evaluate the performance of all the maize maturity groups under the marginal rainfall conditions of the rainforest ecology of south western Nigeria, and t o identify the maize varieties in all the maturity groups that are high yielding under such conditions. Material and Methods Field experiments were conducted at the Obafemi Awolowo University Teaching and Research Farm (7°28'N, 4°33'E, altitude 224 m above sea level) during the late cropping seasons of200l, 2005 and early cropping seasons of 2002, 2006. The treatments were a combination of planting dates and different varieties of maize. Twenty and twenty-one varieties of maize were used in 2001, 2005 and 2002, 2006 late and early cropping seasons respectively. Five and three planting dates at weekly intervals were used in 2001 and 2005 respectively while seven planting dates were used in 2002 and 2006. The planting dates were 20 August-17 September (2001), 13 March-24 April (2002), 7-21 September (2005) and 3 April-24 May (2006). The experiments were laid out as randomized complete blocks in four replicates. Each plot was a single row, 5 m long, spaced 0.75m apart and within row spacing of 0.5 m. Fertilizer NPK was applied at a total rate of 180 kg N, 90 kg P20S and 90 kg K2 0 /ha in two splits; first at three weeks after planting and finally at five weeks after planting. Weeds were controlled by spraying primextra one day after planting at the rate of 5 liters/ha. Weeds were also controlled by hand weeding as necessary after the crop had established. Grain yield and yield components (ear number and weight, ear length and kernel moisture) data were collected. The grain yield data were adjusted to 15% moisture content. The data were analysed as 5 x 20, 3 x 21 and 7 x 20, 7 x 21 factorial experiments in 2001, 2005 and 2002, 2006 late and early cropping seasons respectively, with planting dates and varieties as the factors. Furthermore, regression analyses were performed to determine the trends in response of varieties to planting dates. Significant differences between mean grain yield for all the varieties were compared using the LSD. Results and Discussion Means squares due to variety and planting date effects were significant (P<O.Ol) for all traits measured in 2001 late and 2002 early cropping seasons except for varietals effect for kernel moisture which was not significant (Tables 1). Analysis of variance for the 2005 late and 2006 early copping season’s data produced results similar to those obtained in 2001 and 2002 but for ear length which showed no varietals significant difference (Tables 2). These results were expected as (1) the varieties recorded in the studies were of different 186 A.Oluwaranti et al. maturity classes; including, early, extra-early, intermediate and late maturity, (2) the varieties were bred for different traits such as drought tolerance, downy mildew resistance and streak resistance and (3) the varieties have different genetic backgrounds. The observed significant differences among the planting dates could be ascribed to differences in amounts of rainfall received, which is the most important climatic factor determining the performance of maize in the rainforest zone of Nigeria (F a k o r e d e and A k i n y e m i j u 2003 ). In all the years of evaluation of these varieties under study, the coefficients of variability (CVs) were generally high for grain yield and yield components (Tables 1 and 2). Tab. 1 – Means Squares from the analysis of variance for grain yield and yield components of 20 maize varieties evaluated on five and seven planting dates at the Teaching and Research Farm of Obafemi Awolowo University, lIe-Ife during the late and early cropping Seasons of 2001 and 2002 respectively. *, ** Significant at 0.05 and 0.01 levels of probability, respectively CV = Coefficient of variability YEAR 2001 Sources of variation d.f Ear No Ear Length Kernel Moisture Grain Yield Replication 3 248.450** 14.559** 18.896 3.135 Planting Date (P) 4 948.025** 298.892** 1977.207** 53.455** Variety (V) 19 104.121 ** 8.240** 72.308** 5.501 ** P x V 76 13.058 2.427* 35.786 2.348 Error 297 11.149 1.812 34.347 2.310 Total 399 29.181 5.530 51.880 2.990 CV (%) 28.97 16.45 27.29 50.9

Flour mills, feed mills, breweries as well as breakfast cereal and baby food industries all use maize as the primary raw material.
Observations by F a k o r e d e and A k i n y e m i j u (2003) at IIe-Ife (7°28'N 4°33'E, 244 m) in the marginal areas of the rainforest ecology of south-western Nigeria suggest that the global climatic change is already impacting maize production practices and yield.According to these authors, rainfall at lIe-Ife has been characterized by false starts, which showed a tendency to be more i ntense in the later than earlier years of the period under study.The combination of reduced rainfall and false starts of the rainy season provides an explanation for a shorter cropping season and increased drought probability in March, April and May observed at this location in recent years.S a k a (1997) inferred from the analysis of climatic data collected at the Teaching and Research Farm (TRF) of Obafemi Awolowo University that effective rainy season begins in May and ends in October at lIe-Ife.He concluded that for maize production to be successful, planting should not be done earlier than the first week of April for the early season planting.As for the late season, planting should starts from the fourth week of July to the second week of August to avoid the effect of drought during the grain filling stage of the late season crop ( S o d i m u 1991).More recently, in the United State of America, initiation of corn planting now averages approximately 2 weeks earlier relative to the early 1980's ( K u c h a r i k 2006).It has however been reported by K u c h a r i k (2008) that early planting of maize allows late maturing varieties to give higher yield in comparison to late planting in the Central United States.Wi l l i a m and L i n d q u i s t (2007) noted that crop planting date and canopy density influence interactions between weeds and sweet cor n.They further observed that late planting date resulted in 9% taller crop plants with 36% lower maximum leaf area index (LAI) as a result of weed interference on sweet corn.
As noted by F a k o r e d e (1985), high maize yield can be obtained in the rainforest zone if drought-tolerant or drought-escaping varieties are available to the farmers.Through collaborative research involving maize programs in West and Central Africa, the West and Central Africa Collaborative Maize Research Network (WECAMAN), International Institute of Tropical Agriculture (UTA) and the Maize and Wheat Improvement Center (CIMMYT), Mexico developed early maturing maize varieties that produce dry grains in about 90-95 days and extra early varieties that produce dry grains in 80-85 days and could be eaten as fresh maize in about 65 days after planting.Availability of the early and extra-early varieties is a strategy for adapting maize to the gradually shortening rainy season, so that maize could escape the dr ought stress that occurs during the grain-filling stage in the late season.The early and extra-early varieties were specifically developed for cultivation in the northern fringes of the northern Guinea savanna (NGS) and the Sudan savanna (SS) ( F a j e m i s i n 1989; B a d u -A p r a k u and F a k o r e d e 1999; O n y i b e et al. 1999).Although the early and extra-early maize varieties could also increase maize production under the marginal rainfall conditions of the rainforest zones, their performance in this ecology has not been evaluated.This study was thus conducted to evaluate the per formance of all the maize maturity groups under the marginal rainfall conditions of the rainforest ecology of south western Nigeria, and t o identify the maize varieties in all the maturity groups that are high yielding under such conditions.The experiments were laid out as randomized complete blocks in four replicates.Each plot was a single row, 5 m long, spaced 0.75m apart and within row spacing of 0.5 m.Fertilizer NPK was applied at a total rate of 180 kg N, 90 kg P20S and 90 kg K2 0 /ha in two splits; first at three weeks after planting and finally at five weeks after planting.Weeds were controlled by spraying primextra one day after planting at the rate of 5 liters/ha.Weeds were also controlled by hand weeding as necessary after the crop had established.

Field
Grain yield and yield components (ear number and weight, ear length and kernel moisture) data were collected.The grain yield data were adjusted to 15% moisture content.The data were analysed as 5 x 20, 3 x 21 and 7 x 20, 7 x 21 factorial experiments in 2001, 2005 and 2002, 2006 late and early cropping seasons respectively, with planting dates and varieties as the factors.Furthermore, regression analyses were performed to determine the trends in response of varieties to planting dates.Significant differences between mean grain yield for all the varieties were compared using the LSD.

Results and Discussion
Means squares due to variety and planting date effects were significant (P<O.Ol) for all traits measured in 2001 late and 2002 early cropping seasons except for varietals effect for kernel moisture which was not significant (Tables 1).Analysis of variance for the 2005 late and 2006 early copping season's data produced results similar to those obtained in 2001 and 2002 but for ear length which showed no varietals significant difference (Tables 2).These results were expected as (1) the varieties recorded in the studies were of different maturity classes; including, early, extra-early, intermediate and late maturity, (2) the varieties were bred for different traits such as drought tolerance, downy mildew resistance and streak resistance and (3) the varieties have different genetic backgrounds.The observed significant differences among the planting dates could be ascribed to differences in amounts of rainfall received, which is the most important climatic factor determining the performance of maize in the rainforest zone of Nigeria (F a k o r e d e and A k i n y e m i j u 2003 ).In all the years of evaluation of these varieties under study, the coefficients of variability (CVs) were generally high for grain yield and yield components (Tables 1 and 2).trend was observed (Figure 1).This in corroboration with the findings of Saseendran et al. (2005) as observed in Northeastern Colorado.Grain yield showed decreasing trend for the first five plantings but increased as from the fifth planting date in 2002, on the contrary in 2006, an increasing trend was observed for the first four dates but decreased thereafter.The later part of the late season and the earlier part of the early cropping season are characterized by drought.Therefore optimum planting dates for the maturity classes evaluated in this study are about the middle of August for the late season and mid-April for the early season.

Tab. 3 -Means grain yield (tons/ha) and maturity groups of the 20 maize varieties planted at the Teaching and Research Farm, Obafemi Awolowo University, lIe-Ire in the late and early seasons of2001 and 2002 respectively.
In 2001, most of the early maturing varieties out-yielded the intermediate maturing varieties while the only extra-early variety was among the poorest yielders that season (Table 3).Contrary to what was observed in 2001, the yields of the intermediate varieties were better than the yield of most of the early maturing varieties in 2002 (Table 3).This corroborates the findings of Dwyer et al. (1994) who found in Canada that the later the maturity of maize, the higher the grain yield.In 2005, the drought tolerant varieties (TZECOMP3DT and ACR90POOL16DT) out-yielded the other varieties with grain yield of 1.70 tons/ ha and 1.60 tons/ha respectively (Table 4).Likewise in 2006 early cropping season, these drought tolerant varieties out-yielded most of the other varieties with grain yield of 3.67 tons/ha and 3.83 tons/ha except ACR95TZECOMP4C3 with• 4.37 tons/ha grain yield (Table 4).Generally, the yields of the maize varieties in the early seasons of this study were higher than those obtained in the late seasons (Tables 3 and 4).Data obtained from this study afforded an opportunity to test the hypothesis of Fakorede and Akinyemiju (2003

C o n c l u s i o n
Generally, performance of the maize varieties during the early seasons of 2002 and 2006 was better than that of the late seasons of 2001 and 2005.To obtain optimum yield for the maturity classes evaluated, the varieties must be planted about the end of August or first week of September for the late season and about the middle of April, when the soil would have received enough rainfall for the plant's growth, in the early season.TZEE-WSRBC s and ACR 90 POOLI6-DT with grain yield of3.8 tons ha-1 and 6.4 tons ha- experiments were conducted at the Obafemi Awolowo University Teaching and Research Farm (7°28'N, 4°33'E, altitude 224 m above sea level) during the late cropping seasons of200l, 2005 and early cropping seasons of 2002, 2006.The treatments were a combination of planting dates and different varieties of maize.Twenty and twenty-one varieties of maize were used in 2001, 2005 and 2002, 2006 late and early cropping seasons respectively.Five and three planting dates at weekly intervals were used in 2001 and 2005 respectively while seven planting dates were used in 2002 and 2006.The planting dates were 20 August-17 September (2001), 13 March-24 April (2002), 7-21 September (2005) and 3 April-24 May (2006).
4 .F a k o r e d e , M.A.B. (1985) Response of maize to planting dates in a tropical rainforest location.Expl.Agric 21: 19-30.5 .F a k o r e d e , M.A.B. and O.A. A k i n y e m i j u (2003) Climatic change: effects on maize production in a tropical rainforest location.Pp 272-282 In B. Badu-Apraku, M.A.B Fakorede, M. Ouedraogo, R.J. Carsky and A. Menkir (eds) Maize Revolution in West and Central Africa.Proceedings of Regional Maize Workshop, 14-18 May 2001, IITA-Cotonou, Benin Republic.WECAMAN/IITA.6 .K u c h a r i k C.J. (2006) A multidecadal trend of earlier corn planting in the Central USA.Agron.J. 98: 1544-1550 7 .K u c h a r i k C.J. (2008) Contribution of planting date trends to increased maize yields in the Central United States Agron.J. 100: 328-336 Awolowo University, lIe-Ife during the late and early cropping Seasons of 2001 and 2002 respectively.Tab. 2 -Means Squares from the analysis of variance for grain yield and yield components of 21 maize varieties evaluated on three and seven planting dates at the Teaching and Research Farm of Obafemi Awolowo University, IIe-Ife duringthe late and early cropping seasons of 2005 and 2006 respectively.
1 *, ** Significant at 0.05 and 0.01 levels of probability, respectively Grain yield decreased as planting was delayed in 2001 and 2005 late cropping seasons while in 2002 and 2006 early cropping seasons; a contradicting that availability of early/ extra-early or drought tolerant maize for planting during the early part of the early cropping season would increase maize production in the rainforest zone.TZECOMP3DT, ACR 90 POOL 16 DT, TZEEWSRBC s and TZE-WPOP x 1368STRCI were among the highest yielding varieties in the first three planting dates of the 2002 and 2006 early cropping seasons, which were characterized by drought stress.
1 were the highest yielding varieties at the optimum planting dates in 2001 and 2002 respectively.In 2005 late cropping season, TZECOMP3DT (1.7 tons/ha) was the highest yielding while in 2006 early cropping seasons, ACR 95 TZECOMP4C3 (4.37 tons/ha) was the highest yielding variety.Proceedings ofa Regional Maize Workshop, 4-7 May, 1999, IITA-Cotonou, Benin Republic.WECAMAN/IITA 2 .D w y e r , L. M., B.L. Ma, E v e s o n and R.L. H a m i l t o n (1994) Maize physiological traits related to grain yield and harvest moisture in mid to short season environments.Crop Sci 34:985-992 3 .F a j e m i s i n , J.M (1989) Development of early maturing varieties of maize and potential for increased production in West African semi-arid savanna zones.Paper presented at a Workshop on Appropriate Technologies/or Achieving Sustainable Food Crop Systems in the Semi-Arid Tropical Africa, Ouagadougou Burkina Faso, 11-14 April, 15pp.