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

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

Summary

The research project was initiated in March of 2006; land was cultivated and made into beds on 40 inch centers. Soil samples were collected in March, August, and October 2006 and were tested for nitrogen, potassium, phosphorus and organic matter and pH.

Samples were collected at depths of 0 to 6 inches and 6 to 12 inches. The samples were taken within the center of each plot by compiling 8 cores for the 0 to 6 inch depth and 2 cores for the 6 to 12 inch depth. No additional fertilizer was applied to any plots.

The guar (variety ‘Matador’ PVP #200400235) and pea (variety ‘California #5’) planting occurred at Sunburst Farms on June 2, 2006. Plant stand counts for guar averaged 5 plants per foot for all guar plots. Plant stand counts for black-eyed peas averaged 3 plants per foot for all black-eye pea plots. Irrigation was applied to initiate germination post plant, again before pod set in early July and two weeks later during pod maturation.

The initial harvests for edible biomass began July 2006 at Sunburst Farms. Harvest dates continued for two weeks past initial harvest, totaling 3 harvests. Pods were initially harvested when fifty percent of the pods were at a harvestable stage. The black eye pea harvest peaked with the second harvest. The guar harvest seems to lack a harvest pattern. Both crops were hand harvested.

The guar and black eye pea plots not harvested for edible pods were incorporated with a rototiller when fifty percent of pods were harvestable coinciding with first edible pod harvest. Biomass weight for each plot is the mean of ten plants for center of each plot. Total plant biomass post harvest of edible pods was collected by averaging the weight of 10 plants. Late season rains helped to bolster plant biomass with guar plants averaging 40 inches tall and pea plants measuring 21 inches tall. Guar plants did show nodulation.

Objectives/Performance Targets

The objective of this research was to examine whether guar [Cyamopsis tetragonolaba (L.) Taub.] is a suitable summer cover crop for rotation or as a green manure crop and whether it will provide a suitable marketable product (dry bean or immature pod).

A second objective is to evaluate the benefits of guar and southern peas in rotation with summer squash which will be a follow-up study in 2007. It will analyze soil quality and yield data between the guar and southern pea treatments.

Accomplishments/Milestones

From a vegetable harvest stand point, the black-eyed peas were a much more easily harvested crop. The pods were released from the plant more easily and harvestable pods were more easily identifiable.

The guar pods being much smaller took longer to harvest. The pubescence of the ‘Matador’ variety caused skin irritation. Both pods were sold in Sunburst Market. The black eyed peas sold for $1.50 a pound and the guar sold for $4.00 a pound. The guar was purchased by customers both familiar with the plant and novices to this vegetable. Interest was high compared to actual purchases of the guar pods.

Impacts and Contributions/Outcomes

The data for the first year is still being analyzed by Graduate Student Amy Thiel Jones, and the rotational crop (yellow squash) will be planted in late April or early May of 2007. The results from the guar/southern pea experiments suggest that guar interest is high, especially to those who are familiar with the crop. However, the nature of the guar pods (pubsence that irritates the skin) may be a problem for laborers who hand harvest it. More information will be forth-coming in response of yellow squash to the influence of the rotational guar and southern pea crops.

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