replaced with higher producing Italian ryegrass and nitrogen-fixing white clover. Farmers use a variety of supplementary feeds in winter or during the infrequent summer droughts. Main feeds are hay, grass silage and chopped corn feed. The later is often fed out on a concrete pad to save transportation and wastage by trampling. Manufacturing The manufacturing sector in Waikato contributed $2,688 million in GDP in the year to March 2018, 11.1% of the regional GDP. According to the 2013 New Zealand census, the sector employed 18,519 people, or 9.9% of the region's employed population. With a large dairy farming industry, the Waikato also has a large dairy processing industry. Fonterra operates dairy processing plants at Te Rapa, Te Awamutu, Hautapu, Waitoa, Tīrau and Lichfield. Other dairy processing plants include Tatua Dairy Company's plant at Tatuanui, and Open Country Dairy's plant at Horotiu and Waharoa. The Waikato region has eight major freezing works: AFFCO at Horotiu, Greenlea at Hamilton and Morrinsville, Silver Fern Farms at Te Aroha and Waitoa, Te Kuiti Meat Processors and Universal Beef Packers at Te Kuiti, and Crusader Meats at Benneydale. The Kinleith Mill south of Tokoroa processes wood from the surrounding forests into pulp and paper. History Before the arrival of Europeans, the Waikato contained the third most densely populated part of New Zealand, after Northland/Auckland and the Bay of Plenty. The Waikato rohe (area) was inhabited by iwi (tribes) such as those of the Tainui confederation, including Waikato and Ngāti Toa who conquered the native inhabitants about 1450 according to Tainui historians, finally destroying them at a battle at Aratiatia. Between about 1750 and 1842 the area was subject to a large number of invasions by other Māori iwi and hapu confederations and large scale population migrations took place by a number of hapu and iwi. The largest battle ever fought in New Zealand took place near Ohaupo about 1790–1805, between two competing alliances of hapu. During the latter stages of this volatile period, known as the Musket Wars (1807–1845), conflict led to a migration south to Taranaki and eventually Kapiti Island. In 1840 44 Waikato chiefs travelled north to the Manukau Heads and Manukau Harbour to sign the Treaty of Waitangi, officially making the Waikato area part of New Zealand. Three Ngati Maniapoto chiefs signed, as did three Ngati Haua chiefs but most signatories were Waikato. Chief Te Whero whero did not sign, "probably due