$.extend($.jgrid.defaults, {
    datatype: 'json',
    ajaxGridOptions: { contentType: "application/json" },
    ajaxRowOptions: { contentType: "application/json", type: "PUT" },
    ajaxSelectOptions: { contentType: "application/json", dataType: "JSON" }
});

$.extend($.jgrid.edit, {
    ajaxEditOptions: { contentType: "application/json" },
    recreateForm: true,
    serializeEditData: function(postData) {
        return JSON.stringify(postData);
    }
});

$.extend($.jgrid.del, {
    ajaxDelOptions: { contentType: "application/json" },
    mtype: "DELETE"
});