This figure also shows how soil moisture in its turn has a strong influence on crop production. It does so through several routes: adequate soil moisture provides a buffer and ensures water availability to plants even in the absence of rainfall; soil moisture is essential to mobilise transport of nutrients to and through the plants; and adequate soil moisture improves soil chemical processes and aids the availability in particular of the macro-nutrient, nitrogen. The challenge is not only to increase the availability of water to the land – but also to retain the moisture within the soil. As discussed earlier clay and silty soils have a better capacity to retain moisture. Increasing the organic content of the soil further improves this. Cultivation practices can also improve the retention of soil moisture in the soil – for example, mulching (to avoid evaporation from the soil surface) or deep ploughing (moving moisture to deeper layers), though the appropriateness of such practices are location-specific.