Yuma Ag and You: Summer Rotational Crops

Bobbi Stevenson-McDermott      April 26, 2015 publication

Spring weather is always unpredictable! Wind, heat, cold or stormy, we have it all. For those driving Highway 95 east of Yuma the last few weeks, the crops are significantly different from those grown in January thru March. There are mostly fields of wheat in various stages of growth; Sudan grass; melons; some spring celery harvest; and cotton. For most of the crops, the warm days and cool nights have been great for the development of seedlings and getting them off to a good start. It was amazing to watch the rapid transition of produce fields to their rotation crops.

Crop rotations are very important to the maintenance of the soil health. Most vegetables do not have a large root system and normally it does not extend deeper than 18 inches into the soil. What that means is that some of the fertilizer applied moves below the produce root zone before it is used. In addition, the amount of vehicle and foot traffic in produce production can cause compaction of the soil even below a foot of depth. To restore the soil structure and aeration to the soil, growers use crops with a fibrous root system, similar to Bermuda grass. This large root system extends three or more feet into the soil and is able to utilize the nutrients that are stored in the 2nd and 3rd foot. In addition, the large number of roots break up the compacted layers and allow air and water to move easily in the root zone. After wheat or Sudan harvest, the 2nd and 3rd foot of soil is usually very dry, making it the perfect time for deep ripping or chiseling operations. Any compacted layers remaining will be shattered, providing a better rooting area for the following crop.

Most of the wheat has formed heads and the kernels are beginning to mature. As that happens, the heads become heavy and the plants vulnerable to wind. There are several fields which look like someone has gone through them with a mix master. Wheat is bent over in all directions , called lodging. Some of the plants will recover, but for those bent too far, it can create problems for the grower. Most of the seed heads will continue to mature for harvest, but there are problems with moisture trapped under the lodged wheat, causing slower maturity. Birds love the downed wheat and leave their droppings which can be picked up by the combines during harvest, creating the need to clean the seed before it is graded. Combine operators are challenged to find the best way to harvest these fields to assure maximum yields. Many times it adds costs to the harvest operation. Why some wheat fields lodge and adjacent fields do not can be caused by several factors. Some varieties of wheat may not have sufficient straw strength to support the heads; the root system of the wheat may not have developed enough to support the plant; the wheat heads may have been heavier than usual or the wind hit during irrigation, when the plants were vulnerable. Regardless of the reason, lodging causes extra work and expense for the grower. Yuma farmers would much prefer to see ‘amber waves if grain’!