Open Agriculture. 2017; 2: 600-610 bean genotypes and most of their interactions. Significant correlations were found between all germination variables and between most growth parameters. From the effect of salt application, the common bean genotypes namely KEB-CB049, KEB-CB053 and Mac-33 were the most tolerant while KEB-CB055 and KEB-CB050 were the most sensitive. The results confirm that there is genotypic variation in salinity tolerance and that the most tolerant genotypes should be further explored in selection programs, with the aim that they should be promoted for cultivation in tropical zones affected by salinity.

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Soil salinity represents a major constraint limiting crop production in arid and semi-arid countries. The effect of salinity induced by sodium chloride (NaCl) at five levels (0, 50, 100, 150 and 200 mM) was investigated on four germination traits and thirteen seedling growth characteristics in twenty cowpea [Vigna unguiculata (L.) Walp.] genotypes (ET11, KEB-CP004, KEB-CP006, KEB-CP009, KEB-CP 010, KEB-CP020, KEB-CP033, KEB-CP038, KEB-CP039, KEB-CP045, KEB-CP051, KEB-CP054, KEB-CP057, KEB-CP060, KEB-CP067, KEB-CP068, KEB-CP118, MTA22, NO74 and NO1036). The germination tests were carried out on Petri dishes in the laboratory while seedling growth experiments continued in plastic pots in the greenhouse, both setting up using a randomised complete block design with three replications. Genotypic responses were significant for all germination traits (p < 0.001). Germination percentage, germination rate index, and coefficient of velocity of germination were all decreased by salt stress. However, the mean germination time increased with increasing saline conditions. Significant differences were found between genotypes for most growth attributes. Growth rate (centimeter increased in height per week) decreased significantly with increasing salinity, starting at 100 mM NaCl (24.20% reduction, 2.66 cm / week) with maximum reduction (38.58%) corresponding to 2.16 cm/week observed at 200 mM NaCl, compared to control (3.51 cm/week growth rate). Also, significant decline in shoot weights, number of functional leaves and dry matter production were observed under salinity. Salinity also reduced water content in shoot and root and did not affect root weights. Under salinity, significant correlations were found between all germination variables (p < 0.001). Growth rate was significantly associated with ten out of the twelve other seedling growth traits. Also, the dry matter production under salinity was significantly associated with all other seedling growth characteristics with the exception of root water content. Given the effect of salt stress, cowpea genotypes, namely NO1036, KEB-CP004, KEB-CP038 and KEB-CP051, were the most tolerant while KEB-CP068 and ET11 were the most sensitive ones. The results confirm substantial genetic variation in salt stress tolerance among the studied genotypes. The most tolerant genotypes should be further explored in genetic improvement programs and should be promoted for culture in regions affected by salinity.

Nitrate-N (NO3-N) leaching in intensive crop production systems is an important issue due to its potential as a pollutant and a valuable resource. This study aimed at evaluating NO3-N leaching using on-farm measurements and modeling of 12 commercial fields of leafy vegetables characterized by an array of farm management. Real-time monitoring of the soil moisture, temperature and bulk electrical conductivity using a capacitance/resistance sensor was carried out to verify the temperature index and the leaching constant integrated in the soil nitrogen balance estimation system. Results showed that measured soil temperature strongly correlated to model estimates. Values of the leaching constant were 0.0006 kg kg 1 and 0.00075 kg kg 1 (in 2013) both of which were close to the model value of 0.0007 kg kg 1. Values in 2012 were either too high (0.00127 kg kg 1) or too low (0.0010 kg kg 1). NO3-N leaching ranged from 13.50 kg ha 1 to 72.71 kg ha 1 in 2012 and 8.66 kg ha 1 to 41.10 kg ha 1 or 0.00 kg ha 1 to 41.10 with or without rye, respectively. NO3-N leaching in single cropping systems of 2012 was higher than in double cropping systems of 2013.

Aims: To compare the effects of basalt dust, Tithonia diversifolia (T. diversifolia) powder and NPK 20-10-10 on the growth and production of Garlic (Allium sativum, softneck variety) in Bafut (Cameroon Volcanic Line). Study Design: A randomized complete block design (RCBD) with three replications in the field was used. The treatments were T0 (control), T1 (0.7 tons ha-1 NPK 20-10-10), T2 (0.4 tons ha-1 basalt), T3 (0.6 tons ha-1 basalt) and T4 (0.5 tons ha-1 T. diversifolia powder). Place and Duration of Study: The study conducted in Bafut (Cameroon) from 2nd August 2017 to 24th February 2018. Methodology: Fieldwork involved land preparation, planting and collection of growth and yield parameters as well as rocks and soil sampling. Laboratory work involved soil physicochemical analysis and cutting of rock thin sections for microscopic observations. The plant data were subjected to statistical and economic analyses. Results: The control soil (T0) showed a sandy clayey loamy texture, acidic pH (5.1), very high organic carbon (6.4%), low total nitrogen (0.2%) and moderate available phosphorus (19.42 mg                kg-1). The exchangeable complex revealed high K+ (0.88 cmol (+).kg-1), very low Ca2+ (0.63 cmol (+).kg-1) and Mg2+ (0.21 cmol (+).kg-1), low Na+ (0.07 cmol (+). kg-1), very low sum of exchangeable bases (1.79 cmol (+).kg-1), moderate cation exchange capacity (CEC) (22.7 cmol (+). kg-1) and a very low base saturation (7.88%). C/N ratio was very high (35>17) indicating very poor quality organic matter and a potentially very slow mineralization rate. Growth and yield parameters, except fruit number, were such that T2>T3>T4>T1>T0. T2, T3 and T4 plants gave high yields while T1 recorded the lowest yields below the control. The net yield showed that T3>T4>T2>T0>T1 suggesting that basalt dust and T. diversifolia powder improved soil fertility that in turn boosted yields. Economically, T1 had a BCR (benefit-to-cost ratio)<1 indicative of no profit, while T2, T3 and T4 showed a BCR>2 indicating more than 100% profit of the investment and a possibility of popularization of these treatments. Conclusion: Natural basalt dust and T. diversifolia powder treatments gave better garlic yields indicating a better soil fertilizing capacity compared to synthetic NPK 20-10-10. Basalt dust and T. diversifolia can be popularized to local inhabitants.