Zinc deficiency is a global nutritional problem especially in shale soils of tropical region of south-eastern Nigeria. In view of this, the present study was carried out to evaluate the critical limits of Zn for mungbean producing areas and to establish the optimum rates of Zn fertilizer required to achieve maximum Zn uptake and yield performance of Mungbean. Hydrated Zn sulphate fertilizer was applied to the soils at five levels (0, 5, 15, and 20 kg ha-1) for the greenhouse and at seven levels (0, 3, 6, 9, 12, 15 and 18 kg ha-1) for the field studies. Results shows that, the shale soils were sandy loam (SL), very strongly acidic (4.73), low in OC (1.08 gkg-1), ECEC (4.38 cmol kg-1) and in EDTA-extracTable Zn (0.52 mgkg-1). The critical limits of Zn for mungbean production soils, were established. Results of the greenhouse and field studies shows that levels of Zn significantly (P

Mycorrhiza is obtained from two Greek expressions, namely: mykes (fungus) and rhiza (root). In otherwise, mycorrhiza means fungus-root as coined by Frank in 1885. So, mycorrhiza association is defined as the mutual relationship between fungus and plant root in which the fungus derive carbon from its host plant while the host plants obtain minerals from the fungus. Mycorrhizas are found in different biomes ranging from high latitudes and altitudes, deserts, lowland tropical forest to aquatic ecosystems. It is a known fact that several plants cannot thrive in their natural habitats without this mutualism, as 95-99 % of all plant species have been estimated to belong to genera that generally form mycorrhizas. It is only three families of plant that do not enter into mutual relationship with fungus. These families are as follows: Cyperaceae, Chenopodiaceae, and Brassicaceae. There are now seven types of mycorrhizas among which are arbuscular (AM) endomycorrhiza, ericoid endomycorrhizas, arbutoid endomycorrhizas, monotropoid endomycorrhizas, orchidaeous endomycorrhizas, ectomycorhizas and ectendomycorrhizas. The benefits of mycorrhiza association cannot be overemphasized as studies have shown that it improves nutrient supply of carbon, phosphorus and nitrogen to both plant and fungus that might not normally be made available to plant roots in large amount. It also enhances the performance of plant growing in soils with high amounts of heavy metals and water absorption of desert plants.

The application of zinc to some selected legumes (cowpea - Vignaunguiculata L. Walp., soybean – Glycine max L. Merr. or mungbean - Vigna radiate L. Wilczek) intercropped with upland rice (OryzaesativaL.) may improve the presence of residual nitrogen in the cropping system andprotein in-take of farmers faced with protein and mineral deficiency, especially zinc in their daily food menu. Information on the effect of zinc on legumes and rice is inadequate. The study investigated zinc rate effectsonshoot zinc status, grain yieldand productivity of the crop species in sole and intercrop with upland rice. There were three separate trials laid out in a randomised complete block design with three replications. Zinc rate (0, 2, 4 and 6 Kg•ha-1) were applied to the sole and intercrop in the trials. Intercropping legumes with rice exhibited a high degree of complementarity. On average, 2 Kg Zn•ha-1 gave the highest total land equivalent ratio (LER 1.89) in soybean/rice, followed by 4 Kg Zn•ha-1 (LER 1.64) in mungbean/rice compared to other zinc rates.The application of 6 Kg Zn•ha-1 in cowpea/rice intercrop gave the highesttotal gross monetary and net returns (NR) but lowest benefit–cost ratio (BCR) compared to the other trials at the same Zn rate.In mungbean/rice intercrop,highest NR (₦263692:77•ha−1)and BCR(0.90) were exhibited at 4 Kg Zn•ha-1. The application of 4 or 6 Kg Zn•ha-1in intercropping to the selected legumespecies with upland rice enhanced productivity and financial returns in the systems.

Intercropping fruit vegetable crops with legumes may influence performance of component crops and improve residual nitrogen contribution to the cropping system. Eggplant (Solanum spp.) genotypes whose fruit and leaves are a good source of income and provide essential vitamins and minerals for good health were intercropped with vegetable Cowpea (Vigna unguiculata Walp ssp. sesquipedalis) in 2 years. Eggplant was monocropped using genotypes ‘Ex-Lantan’, Solanum macrocarpon L., S. melogena L, S. aethiopicum L. (mikky mikky-Gilo), ‘Nsukka green’, and ‘Nsukka white’. A semiprostrate vegetable cowpea was grown in monocrop and the crops were intercropped. Eggplant fruit yield, pod yield of cowpea, and interrelationships between yield characters, as well as the biological and economic productivity of the system, were studied. Intercropping eggplant with cowpea produced a high degree of complementarity. The mono- and intercropped eggplant genotypes exhibited wide genotypic variation. On average over two cropping seasons, ‘Nsukka green’/cowpea intercrop followed by ‘Nsukka white’/cowpea intercrop had the highest total land equivalent ratio (LER; 1.78) and land equivalent coefficient (0.79) compared to other mixes. The ‘Ex-Lantan’/cowpea intercrop had the highest mean gross monetary and net returns (NR); the S. melogena/cowpea intercrop produced the highest total cost of production (TCP) among intercrops; the highest benefit–cost ratio (BCR) was for monocropped S. macrocarpon. Among intercrops, the BCR of S. macrocarpon/cowpea mix was highest compared to ‘Ex-Lantan’, S. melongena, S. aethiopicum, ‘Nsukka green’, and ‘Nsukka white’, at 0.57%, 21.58%, 33.46%, 26.30%, and 19.89%, respectively. There was a positive but weak linear relationship between LER and NR and between LER and BCR. Intercropping eggplant with cowpea enhances productivity and financial return.

The study evaluated four soybean genotypes in 2012 and 2013 cropping seasons in the humid tropics for growth, seed yield and other reproductive characters. A split plot in randomised complete block design with four replications was used at National Cereals Research Institute, Amakanma sub-station, Abia State, Nigeria (latitude 05º 28´ N, longitude 07º 29´ E, 154.25 m asl). Sowing date was the main plot treatment while soybean genotypes were fitted into the subplots. Sowing date significantly affected soybean yield and yield components with the month of July pointing out as most appropriate sowing time for the crop in the humid tropics of southeast Nigeria. TGx1485-1D soybean genotype consistently exhibited high performance in seed yield and in most of the characters studied across both environments while TGx1987-10F had the least, hence can be tipped as good breeding material for development of high yielding soybean varieties that would have high adaptation to the agro-ecology. Correlation and path analysis revealed that number of pods plant-1 among other traits was the most important contributor to seed yield and demands close attention as selection index for crop improvement. TGx1485-1D though high yielding exhibited low yield stability across both environments in the GGE bi-plot ranking where it ranked closest to the ideal genotype, hence, can be recommended as suitable for cultivation in the humid tropics of southeast Nigeria. Also, the genotype could be exploited for future breeding programs aimed at boosting research in developing high yielding, adaptable, disease resistance and stable genotypes for the region.

The response of three cucumber varieties (Ashley, Betalpha, and marketmore) to different rates of fertilizer (NPK 15:15:15) application were evaluated in two seasons (early and late) under rain-fed conditions in 2011 cropping season. The experiment was laid out in a split-split-plot in randomized complete block design with three replications. Seasons, (early and late rains) constituted the main plots, while cucumber varieties were fitted into the sub-plots with NPK fertilizer rates into sub-sub-plots. The results revealed significant increase in fruit yield of cucumber during the early planting season under rain-fed conditions in the humid tropics. During both cropping seasons, the application of N:P:K 15:15:15 fertilizer increased fruit yield of cucumber significantly up to 120 kg/ha. However, further increase did not affect fruit yield, which implies that 120 kg/ha fertilizer rate is the optimum quantity required for increased cucumber fruit yield. The interaction between cucumber variety and planting season significantly induced higher fruit yield in market-more compared to the other varieties tested. Principal component analysis showed that PC1, PC2 and PC3 with eigen-vector value loads greater than unity accounted for the cumulative variance of 70%, which exhibited the degree of influence the plant characters had on fruit yield. Pearson correlation indicated a highly significant (P<0.01) and positive correlation between fruit yield and weight of fruit (0.574**) as well as number of fruits per plant (0.574**). Cause and effect analysis revealed that maximum direct effect on fruit yield of cucumber was achieved through fruit weight (0.565) and number of fruits per plant (0.457). This implies that in selection for high yields, premium should be placed on these characters.

Seven promising vegetable cowpea (Vigna unguiculata(L.) Walp)genotypes were evaluated at Michael Okpara University of Agriculture, Umudike, Nigeria (05°29´N, 07°33´E, 122 masl) in 2011 early and late cropping seasons using split plot in randomized complete block design with four replications. Planting season constituted the main plot while vegetable cowpea genotypes were assigned into the sub-plots. The objectives of the study was to evaluate the growth, yield and yield components of seven vegetables cowpea genotypes as influenced by planting seasons in the humid tropics of south eastern Nigeria. The results revealed that planting season significantly (P IT98K-131-1>Akidi-ani>IT03K-324-9>Akidi-enu>IT98K-692>IT99K-377-1. Among the cowpea genotypes evaluated in the study, IT99K-377-1, IT98K-692 and Akidi-enu gave significant pod yields that were higher by 30.46%, 28.86% and 22.38%, respectively compared to the lowest pod yielding genotype (IIT04K-339-1). These promising high yielding genotypes can be evaluated on-farm for farmers’ benefits as well as to enhance food security and improve the protein intake of people living in sub-Sahara Africa.

Thirty-eight high and low cyanide cassava genotypes were evaluated for growth and yield. The experiment was fitted in a randomized complete block design with three replications. Analysis of variance (ANOVA) revealed significant difference (P<0.05) in growth and yield parameters, indicating strong genetic variations among the genotypes. Significant (P<0.05) highest average storage root weight of 1.5 and 1.8 kg were obtained from TMS 94/0035 (high cyanide cassava genotype) and TMS 98/0505 (low cyanide cassava genotype), respectively. Correlation analyses indicated significant (P<0.05) and positive associations between number of storage roots per plant, average storage root weight and root yield in the two types of cassava genotypes tested, indicating that the parameters are good indices that can be improved upon during breeding and selection to enhance root yield. Four high cyanide cassava genotypes (TMS 99/2123, TMS 96/1642, TMS 98/0068 and TMS 94/3200ï´¿ were outstanding in fresh root yield performance. To improve fresh root yield in cassava, the inter-relationships among the various agronomic character of the cassava genotypes demands appropriate attention. The study gives more information on the improvement of fresh storage root yield of cassava. Key words: High cyanide cassava genotypes, low cyanide cassava genotypes, correlations, growth, yield.

The study evaluated the slips of four landraces and five hybrid varieties of white yam for growth and minituber yield in 2011 and 2012 cropping seasons at the National Root Crops Research Institute, Umudike, south east Nigeria. The experiment was laid out in a randomised complete block design with three replications. Landrace Hembamkwase had the longest vine (163.3cm), followed by hybrid TDr 89/02665 while Ame produced the shortest vine. Hembamkwase also out-yielded other genotypes except Ame in 2011 and Nwopoko in 2012. Generally, slips of the hybrid varieties, especially TDr 89/02665 and TDr 97/19177 performed poorly in tuber yield compared to the landraces. Mini-tuber weight showed significant and positive correlation with tuber yield while simple linear regression also showed high coefficient of association between tuber weight and yield. The higher yield associated with the landrace Hembamkwase was attributed to greater slip size, indicating that the landrace can be hybridized and the trait selected for in yam improvement. Keywords : Dioscorea rotundata , yam slips, genotypes, mini-tubers

Field study was conducted during 2001/2002 and 2002/2003 cropping seasons to evaluate the effect of cassava planting methods (horizontal or slanting) and soybean sowing dates (4 and 2 weeks before cassava, simultaneous with cassava, 2 and 4 weeks after cassava) on the yield and yield components and biological productivity of the crop species grown in sole and intercrop. The treatments were arranged in a 2 x 5 factorial laid out in randomized complete block design with three replications. Intercropping significantly (P < 0.05) reduced the yield of cassava and soybean compared with their sole crops. Horizontal method of planting cassava (P < 0.05) depressed yield and yield components of the crop species in the mixture. Soybean yields were generally low due to the shading effect of the cassava component in both cropping seasons. In 2001/2002 and 2002/2003, sowing soybean four weeks before cassava increased grain yield than when sown two weeks before, simultaneously, and two or four weeks after cassava planting. There was no interaction effect between cassava planting method and soybean sowing date in the two cropping seasons. Regardless of the cassava planting method used, soybean sown 4 or 2 weeks before cassava gave the highest monetary returns and net profit than soybean sown at any other time in the mixture or by growing the component crops separately.

The productivity of cassava (Manihot esculentus Crantz)/okra (Abelmoschus esculentus L. Moench) intercropping system as influenced by okra planting density (0; 14,000; 28,000; 42,000 and 56,000 plants/ha) in intercropping with cassava (10,000 plants/ha) were investigated in 2000/2001 and 2001/2002 cropping seasons at Umudike, a rainforest location in south-eastern Nigeria. The results showed that sole cassava plants were shorter than the intercrops between 6 to 12 weeks after planting (WAP) in 2000/2001 but throughout the growing period (6 - 48 WAP) in 2001/2002 as okra planting density in the mixture increased. Similarly, sole okra plants were shorter than the intercropped ones. The leaf production and the leaf area index (LAI) of okra were reduced by high okra planting densities intercropped with cassava. The LAI of cassava increased up to 36 WAP and thereafter declined while in okra it declined up to 10 WAP in both years. It was always higher in sole okra than in the intercrops. Intercropping reduced the total number of tubers but the tuber yield was not affected. Intercropping significantly (P< 0.05) reduced the number of fresh pods, pod length and diameter, pod weight per plant and pod yield/ha. Within the intercrops, okra pod yield was not affected by okra planting density in 2000/2001 whereas in 2001/2002 season, 42,000 plants/ha okra plots yielded higher than the other intercrops. The results showed that it was more productive to grow the two crops together as depicted by yield advantages of 25-30% and that there was higher monetary returns in the mixtures. The optimum okra planting density for intercropping with cassava was 42,000 plants/ha as it had the highest yield advantage of 30% in both seasons and gross monetary returns of N 142,000.00 and N 153,900.00 in 2000/2001 and 2001/2002 seasons, respectively.

SUMMARY A field experiment was conducted during 2002 and 2003 cropping seasons to assess the effect of four N:P:K (20:10:10) fertilizer rates (0, 100, 200, 300 kg/ha) and two cropping systems (sole and intercrops) on the yield and productivity of the component. The treatments were laid out in a split plot arrangement in a randomised complete block design with three replications. The cropping systems were assigned to the main plots and the fertilizer rates were in the subplots. Intercropping reduced the yields of soybean and maize compared with their sole crops. Soybean yields were generally low due to the shading effect of the maize component. Applying fertilizer significantly increased the yield of the component crops in both seasons than when no fertilizer was applied. The results further showed that soybean benefited more from the highest rate (300 kg N: P: K/ha). There was no interaction between cropping system and fertilizer rate in both seasons. The productivity of soybean/maize mixture showed yield advantage of 68 (2002) and 79 % (2003). The highest monetary returns (N72, 717.10 and N87, 165.40/ha) were achieved at the highest fertilizer rate used in the study in soybean/maize intercrop in both cropping seasons. This implies that the optimum productivity and monetary return of the mixture should be investigated beyond 300 kg/ha NPK fertilizer application.

SUMMARY A field experiment was conducted during 2002 and 2003 cropping seasons to assess the effect of four N:P:K (20:10:10) fertilizer rates (0, 100, 200, 300 kg/ha) and two cropping systems (sole and intercrops) on the yield and productivity of the component. The treatments were laid out in a split plot arrangement in a randomised complete block design with three replications. The cropping systems were assigned to the main plots and the fertilizer rates were in the subplots. Intercropping reduced the yields of soybean and maize compared with their sole crops. Soybean yields were generally low due to the shading effect of the maize component. Applying fertilizer significantly increased the yield of the component crops in both seasons than when no fertilizer was applied. The results further showed that soybean benefited more from the highest rate (300 kg N: P: K/ha). There was no interaction between cropping system and fertilizer rate in both seasons. The productivity of soybean/maize mixture showed yield advantage of 68 (2002) and 79 % (2003). The highest monetary returns (N72, 717.10 and N87, 165.40/ha) were achieved at the highest fertilizer rate used in the study in soybean/maize intercrop in both cropping seasons. This implies that the optimum productivity and monetary return of the mixture should be investigated beyond 300 kg/ha NPK fertilizer application.

The effects of three cassava genotypes (NR 8212, TMS 91934 and TMS 30572) grown sole or intercropped with soybean were investigated in two field experiments in 2000/2001 and 2001/2002 cropping seasons at Umudike in the lowland humid forest zone of south-eastern Nigeria. The plant height, canopy diameter, number of leaves per plant and leaf area index (LAI) of soybean and cassava were significantly (P