Arizona, being included in the regions of the desert southwest, alongside New Mexico, and parts of California, has a unique soil and weather conditions that require specific factors when choosing a fertilizer. Here are some tips on how to choose the best lawn fertilizer in the desert southwest:

1. First and foremost, understand your soil. Performing a soil test can help you determine your soil’s pH and nutrient levels. Understanding your soil’s composition can help you select a fertilizer that addresses any deficiencies, like how many areas of the desert southwest have alkaline soils.
2. Choose the right formula, Fertilizers that are labeled as “desert” or “arid region” blends are often formulated to suit the local conditions of the desert southwest.
3. Look out for the nitrogen content on these fertilizers. Nitrogen is essential for promoting healthy leaf and stem growth thus fertilizers with slow-release nitrogen formula are usually what is recommended to ensure a steady supply of nutrients to the grass over time.
4. Other ingredients you should watch out for include phosphorus – since the desert southwest is rich in this nutrient, opt for low to zero level of phosphorus in fertilizers. Another one are micronutrients like iron, magnesium, and sulfur as these can help overcome common deficiencies in desert soils.
5. No matter the fertilizer, it is also important to keep in mind the timing of applying these fertilizers. Applying at the right time can help you maintain your lawn’s health. Spring and early fall are the best seasons to fertilize your soil when your grass is actively growing. Avoid fertilizing during hot summer months when it may stress the grass.
6. Watering can be crucial. Deep and infrequent watering is better than frequent shallow watering. Make sure that your lawn is well-watered before and after applying your fertilizer to prevent possible burning.
7. Remember to always follow the manufacturer’s instructions/label on the fertilizer regarding the application rate and timing. Over fertilizing can possibly damage your lawn.
8. Be mindful of the environment when choosing a fertilizer, use fertilizers in small quantities and avoid runoff into local water systems. Follow all local regulations and guidelines for lawn care products. Organic options are highly advised as well. Look for organic choices that are regionally appropriate.
9. Despite all these tips, sometimes it’s better to consult with local lawn and garden experts in your region. These experts may have insights into local soil issues and can help you choose the right fertilizers for your lawn.
10. Regular lawn maintenance is crucial for ensuring the fertilizer is effectively utilized by your grass. Contact your local landscaping company/ies to help guide you through your chosen fertilizer. Professional help can be of use sometimes.

By considering these factors and customizing your approach based on your lawn and soil’s condition, you can choose the best lawn fertilizer and maintain a healthy and attractive lawn in the desert southwest.