Pearl Millet Nutritional Quality and Fertilization of Sweet Corn in Senegal
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Agricultural production is the main source of income and major employer in many countries in Africa, including Senegal. Commercial sweet corn (Zea mays L. ssp. saccharata) production in Senegal is increasing in response to global marketing opportunities and offers producers the ability to increase income and diversify the cropping base. Production of optimum sweet corn yield and quality depends on adequate nutrient supply, particularly, nitrogen (N). Current N recommendations are based on recommendations specific to corn for grain. This study aimed to identify tools to estimate sweet corn N status and determine the most appropriate fertilizer dosage for sweet corn. Non-destructive remote sensing tools and ion exchange resin membranes (IEMs) were used to evaluate the effect of fertilizer dose. No differences in ear yield or yield components, normalized difference vegetation index (NDVI) values, biomass, N uptake or leaf N concentration due to fertilizer dose were detected at Ndiol. However, significant relationships existed between NDVI values and yield, biomass, and N uptake at the V9 growth stage. Only yield was affected by fertilizer dose at Sangalkam, and no consistent relationships were found between chlorophyll meter readings and others measured parameters. Treatment differences due to fertilizer dose for available NH4+ at V9 (Ndiol), and NO3- at V5 (Sangalkam) were found, however further research is needed to fully evaluate the usefulness of IEMs to measure available soil N. Based on these studies, sweet corn fertilizer rates should likely be based on 75% of the dose applied to field corn, however more work is needed to confirm this finding. Pearl millet (Pennisetum glaucum (L) R. Br.) is the most widely grown staple crop in Senegal. Introduction of drought tolerant millet genotypes has helped mitigate the effect of increased water shortage in the region, but little is known about the nutritional composition of these genotypes. Our objective was to compare millet grain nutritional composition among and between putative drought tolerant and drought sensitive pearl millet lines under drought stress and well-watered conditions. One field experiment was conducted in 2014 at the National Center for Agronomic Research (CNRA) of Bambey, Senegal (16°30' and 16° 28' N; 15o44' and 15o42' W). The experiment utilized a split-plot design with four replications. Water regime was the main plot experimental factor while genotype, a total of 20 was the sub-plot. Pearl millet genotypes were divided into three contrasting groups based on drought tolerance for comparisons. Water stress did not affect 100-grain weight, test weight, protein, soluble protein, starch, sugars, amino acids or vitamin B2 content of grains among VPD-groups. Accumulation of these constituents of pearl millet grain appear to be genetically controlled and are probably not affected by late drought stress. However, differences were noted among genotypes as the sensitive VPD-group accumulated greater soluble protein, starch and soluble sugars (except sucrose) than the tolerant and medium VPD-groups. The tolerant VPD-group, however, accumulated greater protein and vitamin B2 content. Arginine, proline and serine content was greater in the sensitive VPD-group, while lysine, aspartic acid, and glutamic acid were greater in the tolerant VPD-group. Glycine, histidine, threonine, alanine, tyrosine, valine, methionine, leucine, isoleucine, and phenylalanine were relatively equal in tolerant and sensitive VPD-groups. Calcium and Na levels were affected by water stress in the sensitive VPD-group, but differently. Calcium content was greatest for the sensitive group under drought stress, while sodium was the lowest. Iron accumulation in sensitive VPD-group increased under water stress. Potassium decreased for all VPD-groups under stress, while across water regime, K levels in the drought-sensitive group were lower. Selection for drought appears to effect many of the nutritional constituents of pearl millet grain, however many of these differences appear to be directly related to parameters known to effect plant water relations.
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