Use of Guar (Cyamopsis tetragonolaba (L.) Taub) for cover crop rotation and green manuring

• 2006 annual report
• 2007 annual report

This research project was initiated in March 2006 to investigate the potential for using guar (Cyamopsis tetragonolaba) as a fresh-pick commodity for retail sales, and as a rotation option and green manure crop in small farm production. Guar is drought tolerant and a legume that can potentially supply organic matter and nitrogen to crop soils. In this test, organic matter measured following crop production and soil incorporation did not show a significant increase. Crop biomass was greatest with guar that was harvested three times and then shredded late and incorporated when compared to all other crop production treatments. Fresh-picked pod weights were highest with southern peas, and based on total production and potential sales revenues, peas would have an increased value of over $5,000/acre. However, guar sales were better than expected, especially to of various ethnic communities who were familiar with its use. Organic matter showed no changes during the crop cycle (one year) and soil nitrogen, while it increased during the growing season, was not substantially higher during post-incorporation sampling. Growth of a fall-planted wheat cover crop showed no significant differences in biomass production when harvested in the spring. No rotational crop data was available for the second year of this trial due to misapplication of herbicides in the trial area which resulted in crop death. As a result, a no-cost extension of this research has been requested. Overall, the results of this study do show the potential for using fresh guar pods as an additional sales item for local growers, and this may potential increase farm revenues. Although no significant increase in organic matter and soil nitrogen was observed during the trial period, guar should be a useful rotation crop in semi-arid areas of the southern high plains.

Introduction

Sustainable practices help to maintain farming systems by optimizing management of natural resources. Crops which have multiple uses are an integral part in sustainable farming. Environmental and economic concerns for introducing new multi-use crops into production on the Texas High Plains include crop monoculture, soil erosion, limited water, and fields low in fertility and organic matter. An associated concern is limited income markets for the farmer. The main crop grown on the Texas High Plains is cotton with an annual production reaching 3.7 million acres with most grown as cotton following cotton. Lack of rotation contributes to disease and insect buildup. The lack of crop rotation with green manure crops also increases soil erosion, leaves low organic matter, poor tilth, and increased salinity in the soil. Crops grown in monocultures without rotation are usually fertilized with inorganic nutrients. Anhydrous ammonia is a commonly used nitrogen source on the Texas High Plains; however prices of this fertilizer continue to increase significantly. Because cost of inorganic nitrogen fertilizer continues to rise, alternative sources of fertility need to be researched. While adding nutrients to the soil and plants, inorganic fertilizers do not add organic matter to the soil. Amending soils with green manure crops adds organic matter and nutrients to the soil building an improved environment for crop growth. Organic matter improves soil tilth and helps to maintain nutrients in an exchangeable form for plants while also increasing water holding capacity. Lubbock County and the surrounding area are in a semi-arid region receiving an average annual rainfall of 18 inches. Sandy soils of the High Plains have low water holding capacity and expanding urban areas across the Southwest continue to increase the demand for more available water. With limited water resources it is critical to plant agricultural crops tolerant to drought and that have low water requirements. The rising costs of fertilizers and other non-renewable resources and the decline in available water (and increased irrigation costs) are several important reasons for decreased income of farmers. The potential success of using drought-tolerant, low input multi-use crops may stabilize income and other stresses by opening alternative markets. Cover crop rotation and green manure crops not only add organic matter, improve soil tilth, increase water holding capacity, and replace lost fertility, they may also potentially maximize profits during uncertain market cycles.

The objective of this research was to examine whether guar is suitable as a summer cover crop rotation or green manure, and whether its pods may be saleable for the fresh market. Field trials were conducted to evaluate different ways of managing guar followed by a rotation to summer squash and to analyze soil quality and yield data when compared to southern peas.