OPTIMIZED INORGANIC FERTILIZER APPLICATION ON SORGHUM YIELD AND NITROGEN USE EFFICIENCIES IN THE NIGERIAN SAVANNA

ABSTRACT

Sunflower is an important oilseed crop due to its health related values. Induced mutations are often used to create new genetic variability where sufficient variation does not exist naturally as in the case of sunflower. This study was carried out at the laboratory and research farm of the Institute for Agricultural Research (IAR), Samaru, Zaria to assess the response of the sunflower seeds to different EMS doses and determine optimal doses for successful mutation; estimate genetic variability for agronomic traits among the M₂ mutant lines and identify some desirable mutants for oil content and other agronomic traits; assess the degree of association among oil content, grain yield and other agronomic traits and assess the degree of similarity among the selected mutants. Two sunflower varieties (SAMSUN2 and SAMSUN4) obtained from Institute of Agricultural Research were treated with EMS concentrations of 0.1, 0.2, 0.3, 1.0 and 1.5% for 2, 4, 6 and 8 hrs with controls to ascertain optimum EMS concentration and exposure time to bring about desirable mutation. The laboratory study showed progressive decrease in seed germination as EMS concentration and exposure durations were increased. Optimum doses were observed at 0.1% EMS for 6 hrs, 0.2% EMS for 4 hrs, 0.2% EMS for 6 hrs, 0.3% EMS for 4 hrs and 0.3% EMS for 6 hrs for the two varieties out of which 0.2% EMS for 4 hrs, 0.2% EMS for 6 hrs, 0.3% EMS for 4 hrs and 0.3% EMS for 6 hrs were chosen to generate M₁ population in the research farm. A total of 78 M₁ plants with substantial seed set were used to raise M₂ population in progeny rows. Surviving 418 mutant progenies as well as two checks were evaluated for desired agronomic traits in M₂ generation using 16 x 5 lattices design with two replications. The analysis of variance for agronomic traits revealed significant (P<0.05) differences amongst the mutants progenies. Sixty (60) mutants professing higher seed yield per plant (11 – 23 g) were evaluated for oil content. The correlation study showed that grain yield per plant was

ABSTRACT
Groundnut (Arachis hypogeaa L.) productivity in Nigeria has remained low over the years due to the inherent low fertility status of the soils of the savanna, a region where it is mostly grown by small holder farmers with limited imputs. Groundnut can fix atmospheric nitrogen through symbiotic association with native rhizobia but unfortunately, the amount of N2 fixed is usually not enough due to the presence of ineffective or low numbers of native rhizobia. This study was designed to investigate the comparative response of groundnut to rhizobium inoculation and nitrogen fertilizer with or without phosphorus fertilizer on an Alfisol in the Northern Guinea Savannah of Nigeria. Soil samples were collected from a P-deficient plot on the Institute for Agricultural research/ Faculty of Agriculture (IAR/FOA) experimental farms located in Samaru Zaria and used to conduct two screen house trials using the groundnut genotype “SAMNUT 24” as the test crop. The first experiment consisted of six (6) inoculants (four indigenous rhizobial strains namely: SNN 343, KBU 26, SBG 234, SAMFIX 703 one commercial inoculant (HISTICK) and a reference strain (NC 92) alone, the inoculants each combined with 20 kg N ha-1mineral nitrogen as starter dose, and mineral nitrogen alone at 0, 20, or 40 kg N ha-1, adding up to fifteen treatments all termed as nitrogen (N) sources. The second factor was phosphorus at three rates (0, 30 or 60 kg 2O5 ha-1) applied as single super phosphate. The N sources (SNN 343, KBU 26, SBG 234, SAMFIX 703, NC 92, HISTICK, SNN 343 +20N, KBU 26 +20N, SBG 234 +20N, SAMFIX 703 +20N, NC 92 +20N, HISTICK +20 N, 0 kg N ha-1, 20 kg N ha-1and 40 kg N ha-1) and P rates (0 kg P2O5 ha-1, 30 kg P2O5 ha-1
and 60 kg P2O5 ha-1) were factorially combined (fifteen x three) to give a total of forty five (45) treatments and were laid down in a Randomized Complete Block Design replicated three times. The second trial was set up to assess the residual benefit of rhizobium inoculation on following crops. Soils previously inoculated with SNN 343, KBU 26, SBG 234, SAMFIX 703, NC 92 and HISTICK and a control, were combined factorially with three levels of P (0, 30 or 60 kg P2O5 ha-1) to give a total of twenty one (21) treatments. The RCBD was also used with three replications. A non- nodulating groundnut variety (ICGL 5) was included as a reference crop to estimate the amount of biological nitrogen fixed. In the first trial, the use of mineral nitrogen either alone or in combination with rhizobium inoculants suppressed nodulation. Addition of 20 kg mineral nitrogen per hectare to rhizobium inoculation as starter dose reduced nodule number by an average of 12.2 % but increased groundnut shoot dry weight by an average of 9.5 % and 9.8 % compared to inoculation alone and control respectively. The use of this starter dose of mineral nitrogen also increased the amount N2 fixed by 58.4 % compared to inoculation alone and by 51.7 % compared to the control. A similar trend was also observed for % Ndfa. The application of P at 60 kg P2O5 ha-1 gave rise to significant increases in all the parameters measured. However, P uptake efficiency and P agronomic efficiency decreased when P rate increased from 30 kg P2O5/ha to 60 kg P2O5 ha-1. Inoculation alone increased phosphorus uptake efficiency by 29.3 % while addition of starter nitrogen at 20 kg per hectare gave an increase of 35.4 % compared to the control. In the second trial, the residual effects of inoculation failed to produce a significant increase in most of the parameters measured. On average, shoot dry matter declined by 46.3 %, nodule number by 45 %, nodule dry weight by 53 % across all treatments when plants depended on the residual effect of the previous inoculation. Similarly the amount of nitrogen fixed decreased by an average of 34 % across all treatments except KBU 26 which indicates lack of persistence of the rhizobium strains and the need for inoculation with each sowing. KBU 26 amongst all the inoculants increased the amount of nitrogen fixed and % Ndfa by 18.1 % and 52.8 % respectively compared to the first trial indicating that the strains persisted in the soil. The result of this study shows the importance of the use of rhizobium inoculants coupled with a starter dose of mineral nitrogen at 20 kg N/ha to enhance BNF. It also shows that the application of P at 60 kg P2O5 ha-1greatly enhanced yield components and BNF indicating the beneficial role of phosphorus fertilizer on the growth and productivity of groundnut even though P supplied at 30 kg P2O5 ha-1was more efficiently used by the crop than at 60 kg P2O5 ha-1. The residual effect of KBU 26 amongst all the inoculants increased the amount of nitrogen fixed and % Ndfa indicating that the strains persisted in the soil. This potential when fully assessed and harnessed may constitute an evident advantage over the use of inorganic nitrogen fertilizer which has to be applied frequently for consistent high yields.

Bio-fertilizers as key player in enhancing soil fertility and crop productivity

ABSTRACT

Plants nutrients are essential for the production of crops and healthy food for the world’s ever increasing population. Soil management strategies today are mainly dependent on inorganic chemical-based fertilizers, which cause a serious threat to human health and the environment. Bio-fertilizer has been identified as an alternative for increasing soil fertility and crop production in sustainable farming. The exploitation of beneficial microbes as bio-fertilizers has become of paramount importance in agricultural sector due to their potential role in food safety and sustainable crop production. Bio-fertilizer can be an important component of integrated nutrients management. Microorganisms that are commonly used as bio-fertilizer components include;nitrogen fixers potassium and phosphorus solubilizers, growth promoting rhizobacteria (PGPRs), endo and ecto mycorrhizal fungi, cyanobacteria and other useful microscopic organisms. The use of bio-fertilizers leads to improved nutrients and water uptake, plant growth and plant tolerance to abiotic and biotic factors. These potential biological fertilizers would play a key role in productivity and sustainability of soil and also in protecting the environment as eco-friendly and cost effective inputs for the farmers.