Abstract
This study aimed to investigate the effects of compost addition on leaf area index (LAI), diameter growth and enhancement of seed production and quality in Acacia tortilis established under supplementary drip irrigation. Three composted fertilizer doses (2.5 kg, 5 kg and 7.5 kg/tree) were compared to NPK (18-18-5 at a rate of 250 gram per tree) and control unfertilized plots. Effects of compost application on leaf area index (LAI), diameter growth, relative monthly diameter increment (RMDI) were monitored during two consecutive years (2014 and 2015). Then the impacts on pods and seeds production, seed weight, seed number per kg, seed quality (NPK and protein), germination per cent and mean germination time (MGT) were determined. Addition of fertilizers produced high effects on LAI. In 2014 NPK resulted in highest LAI values in most measurements, alternatively the status was changed in 2015 where, higher doses of compost produced higher LAI values. LAI results exhibited temporal variability that was associated with the seasonal variation of the year. The results demonstrate higher RMDI and diameter growth under NPK and compost at rate of 7.5 kg/tree treatments. Pods production was higher in plots treated with higher doses of compost. However, seed/husk ratio was higher in NPK plots. There is observed association between fruit and seed production with LAI. NPK and protein contents in seeds, were also, influenced by the presence of organic fertilizers. Cumulative germination and MGT were correlated with seed weight and were higher in plots treated with compost. The results highlight the importance of organic fertilizers under dry land conditions that produced higher LAI and growth which enhanced seed production and quality.