Django ask for fill a form not required - html

Question

I've a strange bug with my forms.
In a page I must hande 2 separate forms,
the 1st one have no problem at all and I can add the record in DB ,
the 2nd one raise me an error asking to fill a required data of 1st form.
The POST dictionary looks ok
Here the log:
<QueryDict: {'csrfmiddlewaretoken': ['lvt5Ph2SA1xxFK4LMotdHOWk2JuZzYDo0OKWc77rKICYKYmemy3gl0dBphnRNcFb'], 'pk_atto': ['1.1'], 'pk_persona': ['1'], 'capacita': ['11'], 'Aggiungi_persona': ['persona'], 'tipo': ['fondo']}>
<ul class="errorlist"><li>pk_particella<ul class="errorlist"><li>This field is required.</li></ul></li></ul>
the views:
if request.method == 'POST':
if("Aggiungi_particella" in request.POST):
save_atto = AttiPartenzeParticelleForm(request.POST)
else:
save_atto = AttiPartenzePersoneForm(request.POST)
print(request.POST)
print(save_atto.errors)
if save_atto.is_valid():
save_atto.save()
return redirect('/aggiungi_atto_partenza' + '/' + str(save_atto['pk_atto'].value()))
the forms:
class AttiPartenzeParticelleForm(ModelForm):
pk_atto = forms.ModelChoiceField(queryset=Atti.objects.all(),
widget=forms.Select
(attrs={'class': 'form-control'}))
pk_particella = forms.ModelChoiceField(queryset=Particelle.objects.all(),
widget=forms.Select
(attrs={'class': 'form-control'}))
capacita = forms.CharField(max_length=30,
widget=forms.NumberInput
(attrs={'class': 'form-control'}))
tipo = forms.CharField(max_length=30, initial="fondo", widget=forms.TextInput (attrs={'class': 'form-control'}))
class Meta:
model = Acquisizioni_Cessioni_particella
fields = '__all__'
class AttiPartenzePersoneForm(ModelForm):
pk_atto = forms.ModelChoiceField(queryset=Atti.objects.all(),
widget=forms.Select
(attrs={'class': 'form-control'}))
pk_persona = forms.ModelChoiceField(queryset=Persone.objects.all(),
widget=forms.Select
(attrs={'class': 'form-control'}))
capacita = forms.CharField(max_length=30,
widget=forms.NumberInput
(attrs={'class': 'form-control'}))
tipo = forms.CharField(max_length=30, initial="fondo", widget=forms.TextInput (attrs={'class': 'form-control'}))
class Meta:
model = Acquisizioni_Cessioni_particella
fields = '__all__'
and the HTML
<div id="particella" class="content-section d-flex justify-content-center mt-5">
<form action="" method="POST" id="particella_f">
{% csrf_token %}
<fieldset class="form-group">
<div style="visibility:hidden">
{{ form.pk_atto|as_crispy_field }}
</div>
<div class="row">
<div class="col-8">
{{ form.pk_particella|as_crispy_field }}
</div>
<div class="col-2">
{{ form.capacita|as_crispy_field }}
</div>
<div class="col-4 d-flex justify-content-center">
<button form="particella_f" class="btn btn-outline-primary btn-lg mt-5" type="submit" name="Aggiungi_particella" value="particella">
AGGIUNGI PARTICELLA
</button>
</div>
<div style="visibility:hidden">
{{ form.tipo|as_crispy_field }}
</div>
</div>
</fieldset>
</form>
</div>
<div id="persona" class="content-section d-flex justify-content-center mt-5">
<form action="" method="POST" id="persona_f">
{% csrf_token %}
<fieldset class="form-group">
<div style="visibility:hidden">
{{ persona.pk_atto|as_crispy_field }}
</div>
<div class="row">
<div class="col-8">
{{ persona.pk_persona|as_crispy_field }}
</div>
<div class="col-2">
{{ persona.capacita|as_crispy_field }}
</div>
<div class="col-4 d-flex justify-content-center">
<button class="btn btn-outline-primary btn-lg mt-5" form="persona_f" type="submit" name="Aggiungi_persona" value="persona">
AGGIUNGI PERSONA
</button>
</div>
<div style="visibility:hidden">
{{ form.tipo|as_crispy_field }}
</div>
</div>
</fieldset>
</form>
</div>
soneone have any idea?
thx