TOKYO/MUMBAI -- Agricultural chemical companies are increasing investment in India, which boasts a massive farming industry that has been slow to adopt products like weedkillers and pesticides. Japan's Nissan Chemical Industries is slated to open a 6 billion yen ($44 million) plant this month in the western state of Gujarat. The factory is a joint venture with local partner Bharat Rasayan, which handled insecticide production for Nissan Chemical for years, and marks a full-fledged foray into the market.