<div id="data"></div>
<form id='form_id' name='form' method='post' action='' >
<input onblur='FormBlur()' size='10' type=text id='id' name='field' value='Anton'>
</form>

function FormBlur() {
	$("#form_id").on('blur',function(event){event.preventDefault();//что то здесь не так
	var  form = $('form#form_id');
	$.ajax({
                type:"POST",
                url:"/manage/json/",
		data:form.serialize(),
		success:function(data){
			$("#data").html(data);}});
});
}

<div id="data"></div>
<form id='form_id' name='form' method='post' action='' >
<input onblur='this.parentNode.submit()' size='10' type=text id='id' name='field' value='Anton'>
</form>

<div id="data"></div>
<form id='form_id' name='form' method='post'>
<input onblur='alert(this.parentNode.submit)' size='10' type=text id='id' name='field' value='Anton'>
</form>