Arizona Cover Crops & Grasses

Cover Grass and Crop Types

• Davison provides an extensive list of cover grasses that can thrive in Arizona's extreme climate and groups them into a number of useful categories: plants resistant to heat and drought, those that protect soil from erosion and those that are not optimal for growth. Some varieties of cover grass that thrive in high temperatures and require only a modest amount of water include the ground and bush morning glory, bright bead cotoneaster and prostrate germander. Gold lantana and Australian saltbush are particularly effective in protecting soil from erosion. Lastly, Davison suggests that carpet bugle, Algerian ivy, creeping lily turf and wedelia may not be as hardy as other varieties.

  Likewise, cover crops in Arizona can be grouped by their ability to trap nitrogen, improve biomass and prevent the growth of weeds. The Department of Agriculture at the University of Arizona has identified cowpea, lablab and sesbania as the highest producers of above ground nitrogen. Sudangrass and pearl millet produce the most usable biomass. Sesbania is effective in reducing weed growth.

Habitable Zones and Sunlight Tolerance

• There are several factors to consider when selecting a cover grass, including the amount of water needed, tolerance to sun exposure and the climate zone you will be planting in. According to Davison, there are five major climate zones in Arizona. Zones 1 and 2 are low altitude, temperate zones in the northern half of the state, which do not require the use of cover grasses. Zone 3 is high altitude desert, Zone 4 is mid-altitude and Zone 5 is low-altitude desert. A handy map, created by the Department of Agriculture at the University of Arizona (ag.arizona.edu), can help you determine which zone is right for you. You should also determine if your cover grasses can withstand full exposure to sunlight, as with the prostrate acacia, Australian saltbush, ground morning glory and bright bead cotoneaster, or if partial shade is required, as with the desert marigold, gold lantana and creeping lily turf.

  Sudangrass, cowpea, lablab and sesbania are all cover crops with a high sunlight tolerance. However, some species, such as the pearl millet need very little water to thrive. Cowpea, lablab, sesbania, sudangrass and pearl millet are appropriate for Zone 5, or low altitude deserts. These crops, excepting lablab, grow between March and September. Lablab is grown between March and October.

Planting and Watering

• Cover grass varieties that require the least amount of water include the black foot daisy, saltillo evening primrose, mondo grass, green santolina and the clumping gazania. Those that require moderate watering include the ground and bush morning glories, creeping lily turf, prostrate germander, gold lantana and desert marigold. All other varieties of cover grass call for substantial water sources.

  Davison suggests that little soil amendments are needed when planting cover grasses "if you've chosen a species that is adapted to alkaline soils." However, even though many species of cover grass require little watering in the initial planting stages they are particularly delicate. Therefore, you should be sure to irrigate the soil a few days before planting and provide plants with additional water in the first few weeks of growth. Lastly, to preserve water and provide optimal irrigation, Davison states that "soaker hoses, drip irrigation, and micro sprays are the best systems to keep water near the soil level," where it will be most useful to the cover grass.

  One important consideration for cover crops is the leeching of nitrogen into the soil when cover mulches are used with cash crops. To prevent nitrogen from leeching into the soil, do not use legumes like lablab as cover crops in conjunction with cover mulch.