(civil action brought by natural gas company to condemn property owned by defendant; court previously granted injunction permitting gas company to survey property and begin construction with trial on damages decided in this opinion; court determined the value of the permanent and temporary servitudes across two of defendant’s fields as a takings; court held state law determined issue of mitigation and held that leasing affected fields to another to plant corn crop instead of sweet potatoes was not unreasonable due to drainage and irrigation issues caused by plaintiff’s activities, but for portions of the fields not affected by the construction activities, defendant failed to reasonably mitigate its damages, so no recovery is available for those portions; court made award for value of crops on applicable fields, reduced by costs of production, and lease payments received; court also awarded damages for land leveling, drainage cleaning, and soil restoration).