Salt accumulation and ion imbalance caused by residual fertilizer in greenhouse cultivation have been serious problems in Japan since the 1970s. Because an excess of sulfate ions was considered to be one of the causes of these problems, low-sulfate fertilizers were developed to solve this problem. However, when low-sulfate fertilizers were used in root restricted cultivations, chlorophyll indexes were decreased comparing with in the non-restricted cultivations, because total available sulfate resources to tomato plants were limited by rooting zone restriction. The chlorophyll indexes were higher on the treatment covering over soil surface with mulch of silver vinyl film than those of without mulch treatment. Especially, in the drip fertigation, salt accumulation including sulfate was caused on the surface part of soil surrounding area of dripping spot without mulch. Because the condition of rhizosphere of soil surface area was improved as for water and ion concentration by using mulch, the roots distributed there were able to absorb inorganic elements, especially to sulfate ion.