Here are some of the main benefits in landscaping applications:

• Reduces the need for in-organic additives - compost contains most of the plant nutrients found in organic additives.  In some cases it can mean that adding additional phosphate or potassium is no longer necessary.  However, it may not always supply the levels of nitrogen you require, which may mean you need to add a supplement - but at a far reduced rate than normal;
• Helps plants survive better - landscaping often takes place in areas where soil quality is poor.  And yet modern plants need a high level of organic matter to establish quickly.  This can't be provided by fertiliser alone.  Compost contains high levels of organic matter, boosting the physical condition of the soil.  It makes it less bulky, so that roots can penetrate it more easily, allows better airflow and, because of its dark colour, absorbs heat from the sun which improves conditions for germination and growth;  
• Helps soil retain moisture - rain water is held for longer in soils with a high organic content.  This means you have to water it less and plants are less likely to be thirsty when it hasn't rained for a while;
• When used as a mulch it helps prevent erosion and weeds - on light soils in particular, a layer of compost provides excellent protection from the wind and rain.  It also starves weeds of the light source they need to flourish;
• Contains valuable micro-organisms - micro-organisms do three good things to soil.  Feeding off the organic matter in compost, and teaming up with the micro-organisms already present in the soil to which they've been added, they release polysaccarids and humic sustances that help improve soil structure.  They release nutrients in organic matter and make it available to crops to use as food.  They can suppress soil bourne plant pathogens;  
• Cost benefits - although compost purchase and application is a cost to a landscape project, using compost can have cost saving implications.  These include reduced need for fertilisers, reduced watering costs and less money spent on plant replacement.