To start off I'll say my horse is one heck of an easy keeper and I'm not complaining as I've had those hard keepers and that is so much worse Of a problem!  I turn out my horse 12 hours a day on pasture and up on dry lot 12 hours a day. I ride her about 4 times per week, 10 mins trotting, 10 mins loping. I went to a clinic this weekend and she had a difficult time doing a four barrel drill in deep dirt for a prolonged period of time.  With fuel prices where they are I can't afford to haul her 30 mins to ride where there is worked dirt 4 times a week.  So any thoughts or ideas how to get her in better shape to be more prepared for deep dirt when all I have is a dry lot. I do not have a tractor or any heavy equipment. Thank you all in advance!

First of all, it depends on the age of the horse and how heavily you rodeo, as well as his/her physical condition. 

I will write this assuming your horse is no more than 15 years of age, has zero health problems and is sound (but fat! Lol.)

first off, I like to begin with short walk-trot sessions. Monitor how long it takes for your horses heart rate to get back to normal and how quickly he or she cools off. 

Ok, so I'm kinda crunched for time rn so I will try to speed things up... 

Eventually, begin short periods of loping. Going up hill will help too. Begin to build wind. 

Above all, I'd highly suggest trotting or walking hills. If it rains at your place, ride in the mud. One thing I do on colts or full grown horses ththaththat are hard to lope down is I ride them in fields when its muddy too. Lunging in a 60 ft circle is also harder wowork for them.

Once he builds more stamina, all you need to do to keep them legged up (usually) is long trot pastures and breeze. I like to trailer my horses to a track and breeze them there, but if you are careful its not the end of the world if you must breeze on pasture. 

Will add more later. ??

Thank you so much for responding! I do jackpots with good dirt and tend to stay away from rodeos. I hope to compete every 2 weeks or so. My horse is 15, she has lameness issues last year which resulted in 1.5 years off but I've finally got her sound the last 6 months. Otherwise very healthy just fat ?? Where I live everything is flat so I don't have hill option either.

Currently my routine consists of walking 5 mins, trotting 10 mins, loping 10 mins. 3-4 times per week. After this workout she appears to catch her breath within a few mins. But still is overweight and had a difficult time working in the deeper dirt.

Most of us don't have those perfect set ups that allow us to do what is the best for certain things. I only have a field to ride in and no access to hills and my horses are all on dry lots as I don't have enough pasture to keep them out more than a couple hours every so often. I do have a small worked up barrel patch and a round pen, but only use the round pen to work a fresh horse or colt and the barrel patch is set up only for barrel drills and not room for anything else. I have a quarter mile path in my field and when I first start one back in the Spring or after a couple months off, I usually will walk a quarter mile, trot a quarter mile, change directions and then a quarter mile of trotting and then walking to cool off. As long as I am getting the chance to ride consistently, I will then up the distance by a quarter mile each week and just watch their recovery time. For those of us that do not have access to hills, you can always set up cavaletti poles to walk and trot over to help build those muscles. I work my horses up to 2-3 miles a day (depending on if I am going to do drill work also) for at least 3 days a week.My ground is hard but have not had any lameness problems due to the hard ground in the many, many years I have been doing it this way. I had one really fat horse I got that I would base my workout on time because she was so out of shape I could only trot her for 1 minute at a time and then slowly built it up to where I could then move her to distance training.

A lifesaver for me in the last couple years is sending two of mine out for 30 days to work on the water tread (or swim if you have that option). It has been well worth the money since the have so much air built up and really helps with with building the muscles in their back and butt.

Are you doing just Circles/ Straight lines around the lot? I'd try to add something to change it up. I'm not a fan of working full rollbacks every workout but you need to be doing something to work those fast-twitch muscles as well as the distance conditioning you are already doing. 

Can you ride your roadways. If you can and have road ditches .

Ride down them then down thru the ditches around a power pole and back up on the road. Use trees or any obstacles to go around or over. 

Making use of obstacles works to build them up just as good as distance. 

I want to preface this by saying I am not a trainer and I don't have 1D horses. 

I read an article a few years back about Jackie Jatzlau and how she works her horses. I may have the distances wrong (so please don't yell at me), but she mentioned doing about 1/8-1/4 mile walk to her track. Then she would trot/long trot 1/2-1mile, and the lope about 1/2 mile in each direction. Where I used to live I had a small pasture where my horses were and then an open field that I could ride in. I had made a big square out in the pasture and measured it with an app. It was 1/4 mile around. So I would ride one and pony my other horse 2-3 laps in 1 direction trotting and then swap directions. Then I would lope them the same, before walking at least one lap to cool down. They stayed in good shape and stayed very consistent in their respective 3D-5D divisions. I keep somewhat the same riding now at our new home, but I have a big circle that I use and the rest of our pasture. It's approximately 1/10 of a mile from the across the front and down each of side. So I will walk to one "starting point" and then trot up one side, across, and down the other before turning around and repeating 3 times (approx 1 mile). I lope that as well. I also add in loping my big circle and doing smaller circles. I will lope straight down the side of the pasture and then do small circles in each directions to work those muscles. I don't have easy access to soft arena ground either. I live in south Texas. I can take them to a local outdoor arena, but most days it's just not feasible and I would be alone out there as well.

I have since read articles and listened to other trainers tips and tricks on how they work their horses. Hailey Kinsel talks about walking her horses alot and riding for an hour on each horse most days. Now I know we don't all have the time to do that, but when/if you do that can be helpful. Basically I would start increasing your time spent riding to increase your horses stamina. Add in the distance trotting and loping. Do some smaller circles as well as big ones to free them up some. Add some lanscape timbers on the ground to teach them to pick up their feet. Work big cirlces around the barrel and then when you have access soft ground do smaller cirlces.