INFLUENCE OF COMPACTION AND MOISTURE REGIME ON PERFORMANCE OF RHIZOBIUM-INOCULATED SOYBEAN (Glycine max L. Merill) IN AN ALFISOL OF NORTHERN GUINEA SAVANNA OF NIGERIA

INFLUENCE OF COMPACTION AND MOISTURE REGIME ON PERFORMANCE OF RHIZOBIUM-INOCULATED SOYBEAN (Glycine max L. Merill) IN AN ALFISOL OF NORTHERN GUINEA SAVANNA OF NIGERIA

Abstract:

An experiment was conducted to determine the effect of soil moisture deficit (stress), soil compaction and nitrogen sources on performance of soybean. The trial was conducted in two phases; the first was a screen-house experiment in the Department of Soil Science, Ahmadu Bello University, Zaria while the second was a field trial at the University Research Farm of the Institute for Agricultural Research, Samaru, Zaria. The screen house experimental treatments involved three (3) soil compaction levels [no compaction (C0), compaction at 1.3 kg F cm-2 (C1) and 1.7 kg F cm-2 (C2)] , three (3) sources of nitrogen [Legumefix (commercial rhizobium inoculants), Mineral nitrogen fertilizer (20 KgN/ha, urea) and negative control (no rhizobium and nitrogen)] and four (4) levels of available soil moisture deficit [0%, 25%, 50% and 75%] arranged in a factorial combination using randomized complete block design (RCBD) and replicated three times. The field experiment was laid in RCBD in split-split plot arrangement with four (4) available soil moisture deficit level [ASMD (0, 25%, 50%, and 75%) ] as main treatments, two compaction levels [no compaction (C0) and compaction at 1.5 kgF cm2 (C3) (representing conventional and minimum tillage)] as sub-treatments and three nitrogen sources (sub-sub treatment) involving Rhizobium, Mineral nitrogen (20 kg N/ha) and a negative control (without nitrogen). In both experiments, parameters observed were plant height, root length, shoot and root fresh weight, shoot and root dry weight, leaf area, nodule number, nodule fresh and dry weight, bulk density and penetration resistance, nitrogen concentration of the plant. The amount of nitrogen fixed, chlorophyll index, total dry matter, grain yield and hundred seed weight were only observed in the field trial. In the screen-house, soil compaction at C1 significantly (P≤0.05) increased root length by 7.77% and decrease by 5.09% at C3 relative to the control (C0). The result showed that compaction at C0 and C1 were statistically similar in leaf area and both were higher than C3. There was a decrease in nodule number and nodule fresh weight with an increase in soil compaction level. Plant height, root length, shoot and root fresh weight, shoot and root dry weight, leaf area, nodule number, nodule fresh weight, nodule dry weight were found to decrease with each increase in the soil moisture deficit. Nitrogen sources significantly (P≤0.05) influence root length, nodule number and nodule fresh weight. Rhizobium gave the highest mean value for both nodule number and nodule fresh weight compared to mineral N. However, in the field trial, soil compaction had significant (P≤0.05) influence on plant height, root length, root fresh weight, chlorophyll content, soil bulk density (BD) and penetration resistance (PR). There was increase in soil BD with increase in soil compaction level at 0-5 cm, 5-10 cm and 10-15 cm depths except at 15-20 cm where soil BD decreases with increase in soil compaction level. Up to 15.11% increase in PR was observed in the compacted soil over the un-compacted soil. Available soil moisture deficit significantly (P≤0.05) affected plant height, root length, root fresh weight, shoot dry weight, nodule number, total dry matter, and leaf area. The results also showed no significant influence of N sources on these parameters except total dry matter. Accumulation in soybean mineral nitrogen significantly (P≤0.05) increased total dry matter by 27.82% over the unfertilized controlled. The amount of nitrogen fixed by the soybean ranged between 77.02 kg/ha to 152.22 kg/ha. It can be concluded that stressing soybean plant to 25% ASMD would result in similar or even higher yield characters than with full irrigation (0% ASMD). In some cases soybean performance was found to be better in moderately compacted soil (compaction value of 1.3 kg F cm-2). The three nitrogen sources only significantly (P≤0.05) affected total dry matter.

INFLUENCE OF COMPACTION AND MOISTURE REGIME ON PERFORMANCE OF RHIZOBIUM-INOCULATED SOYBEAN (Glycine max L. Merill) IN AN ALFISOL OF NORTHERN GUINEA SAVANNA OF NIGERIA

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