Yield Components Of Maize Research Articles

Maize and Pea Yield and Yield Components of Morphologically Contrasting Maize and Pea Cultivars in Sole and Intercrops in Temperate Conditions

Field experiments were conducted in 2000 and 2001 cropping seasons at the Field Unit of the School of Plant Sciences of the University of Reading at Shinfield to determine the effects on yield of intercropping morphologically contrasting maize and pea cultivars. The maize varieties were ‘Sophy' with a planophile leaf habit and \'Nancis\' with an erect leaf habit. The two pea varieties were \'Maro\' with a normal leaf habit and \'Princess\' with a semi-leafless habit. In both years pea intercropped with maize resulted in smaller maize yields compared to their sole crop counterparts. However the reduction in yield was variable between pea cultivars and years. In 2000 maize intercropped with \'Maro\' resulted in 58% yield reduction and 27% for ‘Princess'. However in 2001 intercropping maize with \'Princess\' reduced yield by 66% compared with 30% for \'Maro\'. Intercropped maize in 2000 had slightly greater harvest index than sole maize. In 2001 maize intercropped with ‘Maro' had the greater harvest index. In 2000 \'Maro\' intercropped with \'Nancis\' had the largest yield whilst in 2001 intercropping pea with \'Nancis\' had comparable yield with sole pea. \'Maro\' in both sole and intercrops in 2000 had greater yield than \'Princess\' whilst in 2001 \'Princess\' in both cropping systems had greater yield than \'Maro\' In both years intercropped pea had consistently more seeds m-2 than sole pea. Mean pea seed weight was greater for intercropped pea in 2000 whilst in 2001 sole pea had greater mean seed weight than intercropped pea. Intercropped pea in 2000 had greater harvest index than sole pea whilst in 2001 sole pea had greater harvest index than intercropped pea. Intercropped maize yields were consistently smaller compared to their sole cropped counterparts but the reduction was greater with normal leaved pea ‘Maro' than the semi-leafless pea \'Princess'. Les expériments du terrain étaient entameś lors de la saison 2000 et 2007. Le lieu d\' expériments était à l\'université de Reading, précisement au terrain de l\' école phytotechnologie de l\'université de Reading à shinfield. L\'objectif était à déterminer les effets sur le rendement morphologiquement opposés. Les variétés du maїs étaient “sophy” et “nancy” avec les caractéristiques hébreuses planophilies et les caractéristiques hébreuses érigées respectivement. Dans le cas des pois, les variétés étaient “maro” et “princess” avec les caractéristiques hébreuses normales et démi-normales respectivement. Dans tous les deux ans, l\'intercalaire des pois et des maїs ont abouti à un rendement réduit dans le cas du maїs par repport à la cultivation unique. Pourtant la réduction en rendement était variable entre les pois et les années. En 2000, l\'intercalaire du maїs et “maro” a abouti à 58% réduction en rendement et 27% dans le cas de “princess”. Pourtant en 2001, l\' intercalaire du maїs avec “princess” a réduit le rendement par 66% par rapport à 20% pour “maro”. L\'intercalaire du maїs en 2000 a indiqué un rendement plus élevé que la culture unique. En 2001, l\'intercalaire du maїs et “maro” avait indiqué un rendement plus éléve. En 2000 l\'intercalaire des “maro” et “Nanci” avait indiqué le plus élevé rendement alors qu\'en 2001 l\'intercalaire des pois et “Nanci” avait indiqué un rendement comparable à pois unique. En 2000, “maro” avait indiqué un rendement plus élevé que “princess” dans tous les deux cas c-à-d la culture unique et la culture intercalaire. Pourtant en 2001 le rendement du “princess” était plus élevé que celui du “maro''. Dans tous les deux ans l\'intercailaire des pois avait régulièrement plus de semences m-2 que les pois unique. Le poids moyen de la semence était plus grand dans le cas des pois intercalaires en 2000 alors qu\'en 2001 le pois unique avait un poids moyen de la semence plus grand que le pois intercalairé. Le pois intercalairé en 2000 avait une plus grande récolte que le pois unique alors qu\' en 2001 le pois unique avait une plus grande récolte que le pois intercalairé. Le rendement du maїs intercalairé était régulièrement petit par rapport à leur éguivalent c-à-d culture unique, mais la réduction était plus grande avec le “maro” que le “princess”. Keywords: Intercropping, plant morphology, maize, pea, yield. Agricultural and Food Science Journal of Ghana Vol. 6 2007 pp. 501-517

Improving the CERES‐Maize Model Ability to Simulate Water Deficit Impact on Maize Production and Yield Components

Crop models are potential tools for designing water‐efficient strategies and should be tested for accurate prediction of water deficit effects on production. The objective of this research was to test and improve the CERES‐Maize model (CERES‐4.0) for ability to predict accurately maize biomass and grain yield components under water‐limiting conditions in an environment where the model had previously given good predictions under irrigated conditions. Under a water‐limited environment in northwest Spain, CERES‐4.0 failed to simulate sufficiently high growth and yield; thus we evaluated aspects of model believed responsible for the poor performance. The model was tested with two evapotranspiration options [Priestley‐Taylor (PT) and Penman–Monteith reference method (PFAO56, FAO no. 56 manual)] and with two values for the coefficient (KEP) that partitions evapotranspiration (ET) between crop transpiration and soil evaporation (default: KEP = 0.685; alternate: KEP = 0.500). The PT option with KEP = 0.685 underpredicted grain yield and biomass due to too early and too severe simulated water extraction. Predictions of biomass and grain yield with both PT and PFAO56 were improved when a KEP of 0.500 was used instead of the default 0.685. The PFAO56, the less water demanding of the tested crop reference (ETo) equations, gave the best predictions. In addition, a systematic underprediction of grain number and grain size with the default model in response to water deficit was observed, regardless of ET option or KEP value. Model predictions of the latter two variables was improved by replacing the default CERES‐4.0 function that computes seed number per plant with the function of Edmeades and Daynard (1979).

Improving the CERES-Maize Model Ability to Simulate Water Deficit Impact on Maize Production and Yield Components

Crop models are potential tools for designing water-efficient strategies and should be tested for accurate prediction of water deficit effects on production. The objective of this research was to test and improve the CERES-Maize model (CERES-4.0) for ability to predict accurately maize biomass and grain yield components under water-limiting conditions in an environment where the model had previously given good predictions under irrigated conditions. Under a water-limited environment in northwest Spain, CERES-4.0 failed to simulate sufficiently high growth and yield; thus we evaluated aspects of model believed responsible for the poor performance. The model was tested with two evapotranspiration options [Priestley-Taylor (PT) and Penman–Monteith reference method (PFAO56, FAO no. 56 manual)] and with two values for the coefficient (KEP) that partitions evapotranspiration (ET) between crop transpiration and soil evaporation (default: KEP = 0.685; alternate: KEP = 0.500). The PT option with KEP = 0.685 underpredicted grain yield and biomass due to too early and too severe simulated water extraction. Predictions of biomass and grain yield with both PT and PFAO56 were improved when a KEP of 0.500 was used instead of the default 0.685. The PFAO56, the less water demanding of the tested crop reference (ETo) equations, gave the best predictions. In addition, a systematic underprediction of grain number and grain size with the default model in response to water deficit was observed, regardless of ET option or KEP value. Model predictions of the latter two variables was improved by replacing the default CERES-4.0 function that computes seed number per plant with the function of Edmeades and Daynard (1979).

Effect of Calcium/Magnesium Ratio in Soil on Magnesium Availability, Yield, and Yield Components of Maize

The effect of calcium (Ca)/magnesium (Mg) ratio in the soil on Mg availability, yield, and yield components of maize (Zea mays L.) was investigated both in the greenhouse and the field at eight different Ca/Mg ratios ranging from 1∶1 and 8∶1. In the greenhouse, exchangeable Ca/Mg ratios of 2∶1 to 3∶1 gave optimum yield of maize without Mg‐deficiency symptoms. The Ca/Mg ratios in the soil were positively and significantly correlated with Ca content and negatively and significantly correlated with Mg content. The Ca/Mg ratio in the soil was also positively and significantly correlated with observed Ca/Mg ratio in the maize plant tissue. The Ca/Mg ratio in the soil could be a limiting factor for Mg nutrition of the maize plant. Under field conditions, exchangeable Ca/Mg ratios in the soil showed no significant effects on the Ca and Mg contents of the maize earleaf. However, optimum maize yield was obtained at an exchangeable Ca/Mg ratio of 6∶1.

The effect of phosphorus(P) placement and genotype differences on yield and yield components of maize(<i>Zea mays L.</i>)

The effect of phosphorus(P) placement and genotype differences on yield and yield components of maize(<i>Zea mays L.</i>)

Effect of some rice based herbicides on yield and yield components of maize

Field trials were conducted during 2001 and 2002 rainy seasons in the Northern Guinea Savanna zone of Nigeria, to evaluate the performance of some pre-emergence herbicides used in rice for weed control in maize. Weed dry weight was significantly reduced by cinosulfuron and the two hoe weedings in 2001 and butachlor in 2002. All the treatments with the exception of piperophos and cinosulfuron significantly increased crop vigour. Plant height and plant dry matter was increased by all the treatments with the exception of cinosulfuron. Cob length of maize was significantly increased by butachlor, oxadiazon and the two hoe weedings in both years. The grain yield of maize was significantly increased by all treatments except piperophos and cinosulfuron and the weedy check in both seasons. These trials show that butachlor and oxadiazon can be used for effective weed control in maize in Nigeria.

EFFECT OF PHOSPHORUS RATES AND METHODS OF ZINC APPLICATION ON MAIZE YIELD AND ITS COMPONENTS

EFFECT OF PHOSPHORUS RATES AND METHODS OF ZINC APPLICATION ON MAIZE YIELD AND ITS COMPONENTS

Influences of irrigation and N fertilization on maize (Zea mays L.) properties

Water quantity and the application period are highly significant for achieving high yield. Also, the best results can be obtained with the proper amount of macro and micro nutrients, especially nitrogen. However, nitrogen is ecologically a very sensitive element. The climatic factors and irrigation have a great effect on the efficiency of fertilization. Therefore, the objective of this study was to examine the effects of supplemental irrigation and nitrogen fertilization on grain maize yield and yield components. The maize grain yield and yield components showed statistical differences between the 2000 growing season (10.64 t ha-1) and 2002 (12.14 t ha-1). Irrigation variant A1 (keeping soil water from 80 to 100% FWC) gave the best results in yield and in all the researched components. Medium (B2) and higher nitrogen level (B3) also gave the best results in the research except grain/ear ratio which had the best results with B1 (100 kg N ha-1). The highest level of irrigation (80-100% FWC) and nitrogen level (200 kg N ha-1) did not give statistically significant higher yield and yield components. Applying 150 kg N ha-1 in the year 2000 also proved environmentally suitable quantity of nitrogen on the researched soil since the higher level of N (B3) did not increase the yield.

MAIZE (ZEA MAYS L.) GROWTH AND YIELD RESPONSE TO ETHEPHON APPLICATION UNDER WATER STRESS CONDITIONS

The aim of the present investigation was to study the growth, yield and yield components of maize (Zea mays L.) single cross 704 under different levels of irrigation, plant density, and ethephon in southern Iran where this particular crop has not yet been studied in detail. A field experiment was performed in the 2004 5 growing season at the experimental farm of the College of Agriculture, Shiraz University, Shiraz, Iran, located at Badjgah. The experimental design was a randomized complete block with four replicates where the treatments had a split split plot arrangement. Irrigation level (low and high) was the main plot, plant density (53,333 and 80,000 plants/ha) the subplot, and ethephon level (0, 0.56, 0.84 kg/ha a.i., applied at the 6 leaf stage) the sub subplot. The results showed that the rates of foliar application of ethephon could play an important role in maize growth indices, and attribute to grain yield components. Application of ethephon was associated with a decrease in Leaf Area Index (LAI), Leaf Area Index Duration (LAID) and Crop Growth Rate (CGR). Furthermore, ethephon reduced plant and ear height. Increasing the application rates of ethephon showed a significant reduction in early season plant height and LAI, LAID. The control plants had lower grain yield than those treated with different rates of ethephon. Indeed, this research showed that under conditions of water stress, the maize plant is able to make better use of available water if vegetative growth is partially restricted early in the season. The results also indicated that the yield response of maize to ethephon application would vary with plant density and available water conditions. Ethephon treatment was found to be more beneficial for grain yield with higher plant densities and under water stress conditions.

Epistatic interaction is an important genetic basis of grain yield and its components in maize

A population of 294 recombinant inbred lines (RIL) derived from Yuyu22, an elite maize hybrid extending broadly in China, has been constructed to investigate the genetic basis of grain yield, and associated yield components in maize. The main-effect quantitative trait loci (QTL), digenic epistatic interactions, and their interactions with the environment for grain yield and its three components were identified by using the mixed linear model approach. Thirty-two main-effect QTL and forty-four pairs of digenic epistatic interactions were detected for the four measured traits in four environments. Our results suggest that both additive effects and epistasis (additive × additive) effects are important genetic bases of grain yield and its components in the RIL population. Only 30.4% of main-effect QTL for ear length were involved in epistatic interactions. This implies that many loci in epistatic interactions may not have significant effects for traits alone but may affect trait expression by epistatic interaction with the other loci.

Effect of tillage system and nitrogen fertilization on yield and yield components of maize in Western Ethiopia

The western part of Ethiopia has a high maize production potential as a result of favourable environmental conditions. However, maize production is constrained by non-sustainable cropping practices, particularly plough- or hoe-based cultivation, soil and water loss due to erosion, as well as N deficiency. Experiments were therefore conducted to determine the integrated effects of tillage system and N fertilization on the productivity of maize from 2000 to 2004 at five sites. Three tillage systems (MTRR = minimum tillage with residue retention, MTRV = minimum tillage with residue removal and CT = conventional tillage) and three N levels (the recommended rate and 25% less and 25% more than this rate) were combined in factorial arrangement with three replications. The recorded grain yield in the experiments ranged from 4649 to 8030 kg ha−1 with an average of 6104 kg ha−1. Grain yield was positively and significantly correlated with several yield components, especially total biomass yield and thousand seed weight. During the initial two years of the experiments, there was no significant difference in grain yield between MTRR and MTRV and both were significantly superior to CT. However, during the final two years of the experiments, there was no significant difference between MTRV and CT and both were significantly inferior to MTRR. On average, MTRR increased grain yield by 6.6 and 12.2% compared to MTRV and CT, respectively. The application of N increased grain yield regardless of tillage system and the recommended fertilization rate of 92 kg N ha−1 for conventional tilled maize was also found adequate for minimum tilled maize. These results proved that MTRR can be introduced successfully in western Ethiopia.

Yield components of nodulated cowpea (Vigna unguiculata) and maize (Zea mays) plants grown with exogenous phosphorus in different cropping systems

A 2-factorial experiment, involving three levels of phosphorus (0, 40, and 80 kg/ha) and four cropping systems (mono crop, maize–cowpea inter-row, maize–cowpea intra-row, and maize–cowpea intra-hole cropping) was conducted in the field for two consecutive years in 2003 and 2004 at Nietvoorbij (33°54′S, 18°14′E), Stellenbosch, South Africa. Plant density (number of plants per hectare) was 166 666 for sole cowpea, 111 111 for maize–cowpea inter-row, 55 555 for maize–cowpea intra-row and 55 555 for maize–cowpea intra-hole cropping. Applying 40 or 80 kg phosphorus (P)/ha significantly increased cowpea grain yields by 59–65% in 2003 and 44–55% in 2004. With maize, the increases in grain yield were 20–37% in 2003 and 48–55% in 2004 relative to the zero-P control. In both cropping seasons, the number of pod-bearing peduncles per plant, the number of pods per plant, the number of seeds per pod, and grain yield per cowpea plant were significantly increased with the application of exogenous P. In contrast, the number of pod-bearing peduncles per plant, the number of pods per plant, the number of seeds per pod, and the grain yield per plant were all significantly depressed by mixed culture relative to mono crop cowpea. There was also a significant interactive effect of P and cropping system on cowpea, such that, all cowpea yield components were generally lower in intercrop relative to mono crop. In all instances, the yield component of mono crop cowpea and, to some extent, inter-row cowpea, were markedly increased by the provision of 40 or 80 kg P/ha relative to the zero-P control. Intercropping maize with cowpea produced higher total yields per unit land area than the mono crop counterpart.

Optimum lateral spacing for drip-irrigated corn in the Mediterranean Region of Turkey

This study was carried out to determine the effects of different lateral spacings, and the full and deficit irrigation on yield and yield components of maize under the Mediterranean climatic conditions in Adana, Turkey. Experimental site was located at the Research Field of the Agricultural Structures and Irrigation Department (altitude 20 m above sea level, 36°59′N and 35°18′E) on a clay textured soil. Pioneer 3394 hybrid corn variety was used in this study. Irrigation treatments consisted of three different lateral spacings ( A 1: 0.70 m, A 2: 1.40 m, and A 3: 2.10 m) and two different water amounts ( I 100, I 67). In the I 100 treatment, soil water deficit in the 90 cm soil profile depth was replenished to field capacity. For deficit irrigation treatment I 67, 33% less water was applied as compared to I 100 treatment plots. A 7-day irrigation interval was used in the study. The highest seasonal water use (ET) was determined in the A 1 I 100 treatment as 758 mm; and the lowest ET was found in the plant row 1.05 m away from the drip lateral in the treatment A 3 I 67 (569 mm). Lateral spacings and irrigation levels resulted in significantly different yields. The highest grain yield was obtained in A 2 I 100 treatment with 9790 kg ha −1, and the lowest yield was found in the plant row 1.05 m away from the drip lateral in A 3 I 67 treatment with 6180 kg ha −1. Yield from the 1.4 m spacing with full irrigation treatment ( A 2 I 100) was significantly higher than in the other two spacings. According to the research results, optimum lateral spacing for corn plant was found to be 1.4 m. Significant second degree polinomial relationships between corn grain yield ( Y) versus irrigation water ( I) and water use (ET) were found as Y = −0.0037 I 2 + 5.835 I − 1397.7 ( R 2 = 0.62 **) and Y = −0.0039ET 2 + 5.926ET − 1365.1 ( R 2 = 0.54 *), respectively. The highest water use efficiency (WUE) was found in A 2 I 100 (1.40 kg m −3) and the lowest one was found in the plant row 1.05 m away from the drip lateral in A 3 I 67 (1.09 kg m −3). Thus a lateral spacing of 1.4 m (one drip lateral per two crop rows) was recommended for drip-irrigated corn in the Mediterranean Region under those specific conditions.

Quantitative trait loci mapping and epistatic analysis for grain yield and yield components using molecular markers with an elite maize hybrid

The aim of this investigation was to map quantitative trait loci (QTL) associated with grain yield and yield components in maize and to analyze the role of epistasis in controlling these traits. An F2:3 population from an elite hybrid (Zong3 × 87-1) was used to evaluate grain yield and yield components in two locations (Wuhan and Xiangfan, China) using a randomized complete-block design. The mapping population included 266 F2:3 family lines. A genetic linkage map containing 150 simple sequence repeats and 24 restriction fragment length polymorphism markers was constructed, spanning a total of 2531.6 cM with an average interval of 14.5 cM. A logarithm-of-odds threshold of 2.8 was used as the criterion to confirm the presence of one QTL after 1000 permutations. Twenty-nine QTL were detected for four yield traits, with 11 of them detected simultaneously in both locations. Single QTL contribution to phenotypic variations ranged from 3.7% to 16.8%. Additive, partial dominance, dominance, and overdominance effects were all identified for investigated traits. A greater proportion of overdominance effects was always observed for traits that exhibited higher levels of heterosis. At the P ≤ 0.005 level with 1000 random permutations, 175 and 315 significant digenic interactions were detected in two locations for four yield traits using all possible locus pairs of molecular markers. Twenty-four significant digenic interactions were simultaneously detected for four yield traits at both locations. All three possible digenic interaction types were observed for investigated traits. Each of the interactions accounted for only a small proportion of the phenotypic variation, with an average of 4.0% for single interaction. Most interactions (74.9%) occurred among marker loci, in which significant effects were not detected by single-locus analysis. Some QTL (52.2%) detected by single-locus analysis were involved in epistatic interactions. These results demonstrate that digenic interactions at the two-locus level might play an important role in the genetic basis of maize heterosis.

Response of Maize to Different Levels of Sulfur

A field experiment was conducted to assess the effect of different levels of sulfur (S) on yield and yield components of maize crop grown on silt loam soils at the Agriculture Research Station Baffa, district Mansehra. The soil contained 1.17% organic matter, 10% CaCO3, and 39 mg SO4‐S kg−1. Sulfur was applied at 0, 20, 40, 60, 80, 100, and 120 kg ha−1 as gypsum along with 120 kg N, 90 kg P2O5, 60 kg K2O ha−1 replicated thrice in RCB design. Soil samples at silking and harvesting stage from each treatment plot along with leaf samples were collected for the determination of S. Yield and yield components of maize were significantly (p<0.05) enhanced with the application of S compared with control. Sulfur at 60 kg ha−1 produced highest yield of fresh matter, dry matter, stover, 1000‐grain and total grain, resulting in increases of 41, 55, 58, 5, and 43%, respectively. Application of S above 60 kg S ha−1 reduced yield and yield components, suggesting a classical yield response curve. The analysis of soil samples at silking and harvesting stage from each treatment plot revealed that soil SO4‐S concentration increased significantly by S application reaching the level of 108.4 and 99.7 mg kg−1, respectively, with 120 kg S ha−1. Sulfur concentration of leaves was significantly increased with the application of S compared with the control. Application of sulfur at 60 kg ha−1 produced leaf S concentrations of 0.46%, which is less than the critical level of 0.5%, whereas higher treatments increased S concentration ranging from 0.67 to 0.94%, which exceeded the value considered as high (0.5%) and excessive (0.8%). Elevated tissue sulfate concentrations induced by treatments greater than 60 kg ha−1 corroborate with the corresponding yield decreases of maize. Maize growers of the area may add S up to 60 kg ha−1 to obtain maximum yield.

INTERCROPPED WITH GROUNDNUT ON GROWTH, YIELD AND YIELD COMPONENTS OF BOTH CROPS

Two field trials were carried out at South Tahrir Research Station (Ali- Moubark). These trials were conducted in 2003 and 2004 to evaluate three planting dates of maize (the over story shade crop) intercropped with groundnut i.e, on 1st June, 10th June and 20th June, and four plant densities of maize intercropped with groundnut, i.e, maize was spaced at 50 and 100 cm apart leaving one or two plants/hill. Groundnut (the main crop) was grown on all rows. The data obtained indicate that ear length, ear diameter, number of rows/ear, number of kernels/row and the weight of 100grains increased with increasing maize spacing as well as with diminishing the number of plants remained per hill after thinning (to one plant/ hill). On other hand dense planting resulted in higher yield of maize whether by narrowing maize spacing or increasing the number of maize plants per hill after thinning. Yield and yield components of maize were significantly decreased by delaying planting date of maize up to the latest date. Yield /fed and yield components of groundnut were associated with maize density and distribution. The more the shade offered by maize the less the values of these traits were obtained. Highest values were obtained when maize was spaced at 100cm. and thinned to one plant/ hill. Increases in the values of yield and yield components of groundnut were associated with delaying the planting date of maize. Delaying the planting date of maize resulted in increases in the values of land equivalent ratio (LER) and the relative crowding coefficient. The treatment effect at any planting date of maize exerted very low competitive pressure when aggressivity was measured. With delaying seeding maize, competitive ratio (CR) diminished to the least. Spacing maize at 50cm. apart and leaving two plants / hill after thinning resulted in highest value of LER and relative crowding coefficient (RCC). Nor any maize density had any heavy competitive pressure on groundnut when aggressivity was measured

The effect of a high selection intensity on the change of maize yield components' additive variance

A set of 31 SSD lines from ZP-Syn-1 Co and 37 from ZP-Syn-1 C3 maize population was studied in this paper. After line selection and seed multiplication in 2000, the trials were carried out in 2001-2002. at Krusevac and Zemun Polje, in RCB design. After three cycles of recurrent selection we observed a significant decrease of homozygous progenies' means of root and stalk lodged plants percent, plant and ear height, but also of row number per ear. The means of grain number per ear and 1000 grain mass were increased, and the differences in ear length and grain yield were not significant. After three cycles, a significant narrowing of additive variance happened for root and stalk lodged plant percent, ear length, and row number per ear, but this narrowing was not significant for the other traits. We also found significant values of narrow-sense heretability.

Control of Imperata cylindrica (L.) Raeuschel (speargrass) with nicosulfuron and its effects on the growth, grain yield and food components of maize

Imperata cylindrica (speargrass) is one of the most invasive weeds in the moist savannah zone of sub-saharan Africa. This study was conducted in 2001 and 2002 at Ijaye and Ilorin, Nigeria, to investigate the influence of four nicosulfuron doses (35, 70, 105, and 210ga.i./ha) on the performance of maize, and its efficacy in the control of Imperata. The experiment was designed as a split-plot with three replications. Nicosulfuron was applied 2 weeks after planting maize. Hoe weeded and unweeded treatments were controls. In both years, 7 weeks after treatment, the unweeded control had lower maize leaf area index (LAI) (19% at Ijaye and 25% at Ilorin) than the weeded control. Maize LAI was highest in plots that received 35ga.i./ha of nicosulfuron at Ijaye and the weeded control at Ilorin in both years. All plots that received nicosulfuron had significantly higher maize grain yield than the unweeded control at both locations in both years. Maize grain yield in the weeded control was similar to plots that received nicosulfuron at 35–210ga.i./ha at Ijaye in 2002, 70–210ga.i./ha at Ilorin in 2001, and 35ga.i./ha at Ilorin in 2002. The protein content of maize in the weeded control and at 70ga.i./ha was similar and higher than that at doses of 105 and 210g a.i./ha (P⩽0.01) while the carbohydrate content was not significantly different. The unweeded control had significantly higher weed LAI, shoot and rhizome biomass than all other treatments at both locations in both years (P<0.05). An increase in the nicosulfuron dose led to a decrease in weed LAI. Imperata rhizome biomass in the weeded control was similar to that in all nicosulfuron-treated plots. The findings of this study show that nicosulfuron is a suitable postemergence herbicide for speargrass control in maize in the moist savannah of Nigeria.

Model Concepts to Express Genetic Differences in Maize Yield Components

Maize (Zea mays L.) grain yield is closely related to kernel number per unit area. The quantification of genetic differences among maize cultivars to kernel number plant−1 (KNP) is critical for accurate yield simulation but remains one of the less accurate components of yield modeling. Our objective was to document the recently published KNP data and revise CERES Maize model (V3.5). The duration of a critical window for KNP simulation was 327°C days (227°C days before and 100°C days after silking—base temperature 8°C) when ears actively grew. The KNP was curvilinearly related to cumulative intercepted photosynthetically active radiation plant−1 (CIPAR) during the critical window. Potential kernel ear−1 and kernel produced per unit CIPAR were the genetic coefficients needed to simulate KNP. Apical ears produced maximum KNP at a plateau CIPAR of 64 MJ, and prolific hybrids produced secondary ears when CIPAR exceeded 64 MJ. The genetic differences in prolificacy in low plant density were expressed by another coefficient. Below a threshold CIPAR of 11 MJ, all plants were barren, and a barrenness coefficient expressed genetic differences among old and modern hybrids to produce KNP in high plant density. Sensitivity analysis with limited testing indicated that the revised model simulated yield reasonably well [root mean square error (RMSE) = 0.63 Mg ha−1] compared with the original model (RMSE = 1.25 Mg ha−1) across a wide range of plant densities. However, rigorous testing of the model will be required to gain greater confidence in the proposed concepts.

Model Concepts to Express Genetic Differences in Maize Yield Components

Model Concepts to Express Genetic Differences in Maize Yield Components