Effect of Pymarc with NPK 17-17-17 and intra-row spacing on soil and bush bean (Phaseolus vulgaris L.) yield in volcanic highland, Rwanda

Bush bean is the poor families’ meat in Rwanda and grown in many corners of the country. However, unevenness application of organic and inorganic  amendments brought soil degradation including soil toxicity or deficiency and low bush bean production. The objective of this study was to evaluate the  effect of pymarc rates with NPK and spacing on Soil organic matter, physical parameters and bush bean yield parameters in volcanic highland. The design  was RCBD with four replications and the experiment had two factors; Pymarc rates: P0(control), P1(250Kg ha-1 NPK), P2(10 tons ha-1 pymarc+250  Kg ha-1 NPK), P3(15 tons ha-1 pymarc+250Kg ha-1 NPK) and P4(20 tons ha-1 pymarc+250Kg ha-1 NPK) and spacing levels: S1(40cm x15cm), S2(40cm x  20cm) and S3(40cm x 30cm). Results showed that, highly significant difference (p<0.01) was in treatments and greatest improvements were brought out  by P2S1 with lowest Bd(0.95 g cm-3), highest WHC(38.34 %) and porosity(42.18 %) at harvesting with mean yield of 3.03 t/ha compared to P0S3 with least  values of studied attributes. Highest SOM content was found out in P4S3 and P3S1 of 9.84 % and 9.75 % sequentially. The correlation analysis results  between WHC, Porosity, SOM and yield varied from weak to strong (0.4>r, r>0.7), significant (p<0.05) and positive while the same relationship but negative  existed between Bd and other parameters. Therefore, sowing the bush bean at the spacing of 40cm x15cm with application of 10t  ha-1 pymarc+250 Kg ha-1 NPK 17-17-17 could be recommended to agronomists and farmers from volcanic highland in Rwanda for bush bean optimum  yield.