Could winter-planted garbanzos be a rotational crop for Kern County dry bean growers in a drought situation?
That remains to be seen, but the possibilities were discussed at a dry bean field day at the University of California Research and Education Center at Shafter.
Shannon Mueller, Fresno County farm advisor, reviewed production practices and research for garbanzos, citing their ability to draw deep moisture and reduce fertilizer costs by fixing nitrogen in the soil.
Garbanzos, also known as chickpeas, attracted grower interest in the central San Joaquin Valley as a fall or winter planted crop in the water-short early 1990s as a replacement for winter wheat and other cereals. Until that time they were mainly a summer dryland crop in coastal counties. Over the next 10 years SJV garbanzo acreage increased.
During the late-1980s and 1990s, several trials on clay-loam soils of the West Side Research and Education Center (WSREC) at Five Points were done on planting dates ranging from November to March. Mueller recalled that at first, the earlier dates brought higher stands and in most cases yields followed that trend.
“However, when disease was a factor, such as plots planted in mid to late November of 1996, the advantage of early planting in establishing a good stand was lost by greater susceptibility to disease, which significantly impacted yield,” Mueller said.
Ascochyta blight, Sclerotinia stem and crown rot, and other viruses appeared in time and clouded the planting timing issue. Results depended on weather conditions, and when diseases and insect pests occurred. Mueller said as improved varieties with resistance and seed treatments are adopted, some advantage with earlier plantings for better stands and yields might be expected.
Seeding rates, evaluated at from 60 to 100 pounds per acre, also varied in success. In the early trials, the higher the seeding rate, the better the stand and the higher the yields, but then as diseases and viruses came in it became difficult to predict.
“In general,” Mueller said, “our recommendation would be higher rates, although garbs do have the ability to compensate for significantly reduced stands.” In one of her trials, plant population was reduced by more than 40 percent by vertebrate pests, but yields were only down about 16 percent.
Turning to irrigation, she said the crop typically takes about 25 inches of water. In 1994, when winter rainfall at the WREC trials was 7 inches, about 20 percent (4.8 inches) of the seasonal water use occurred during the first 90 days after planting (January through March). Crop ET accelerated with bloom and bean set during April and May to use 61 percent of the total (15.2 inches) and the remaining 19 percent occurred mainly in June with slight consumption during early July before harvest.
“We also measured where garbanzos take up water,” she said. “They have a deep tap root and can take water from 5 feet in the soil. They took 44 percent of the seasonal water from the top foot of soil, and the second, third, and fourth feet of soil contributed 19 percent, 17 percent, and 12 percent of water needs, respectively. The crop took on average 7 percent of its seasonal water from the fifth foot of soil.”
Fertilizer trials were done at WSREC and on commercial fields to evaluate effects of supplemental nitrogen on yield and quality.
Preplant rates of zero, 80 and 110 pounds of nitrogen per acre were used as granular urea (46-0-0) was applied. The trials showed yield responses to the additional nitrogen supplied. They also traced effects of additional irrigation with the fertilizer rates.
“Preplant nitrogen rates did not affect bean size at a statistically significant level,” she said. “However, as yield increased with additional water, bean size was slightly reduced. Additions of preplant nitrogen not only increased yield, they also maintained more desirable bean size in the more intensive irrigation treatments.”
Pointing out the crop is an efficient user of nitrogen, and when inoculated with Rhizobium bacteria can fix nitrogen in the soil, she added that “supplemental nitrogen has helped ensure higher yield and bean size, and this was more evident in wet years or with later spring irrigations which promote vegetative growth.”
In discussing disease management in garbanzos, Carol Frate, Tulare County farm advisor, said the main concerns are aphid-borne viruses, Ascochyta blight, and Sclerotinia stem and crown rot.
The best defense against the complex of viruses is having an established stand when aphids arrive. Infections can be particularly severe to garbanzos if alfalfa, which also hosts the viruses, is nearby.
Ascochyta, recognized by tan spots and lesions that develop characteristic concentric rings, reduces yields sharply and is spread by splashing water from rain or sprinklers. Developing beans can become infected and cause early infections in the next crop. The disease has no other known crop or weed hosts.
Among management components for Ascochyta are avoiding sprinkler irrigation, use of resistant varieties, use of seed that is clean or treated with Mertect, at least two years between garbanzo crops in the same field, and destruction of crop residue and volunteers.
Sclerotinia, a problem when rain is followed by fog, produces sclerotia that can survive in the soil for years until conditions are right for an outbreak.
Among management steps for it are selection of fields with no history of the disease, later planting (in December or early January), and deep plowing to bury sclerotia 6 to 8 inches below the surface.
Frate said it is unknown whether Sclerotinia on alfalfa can infect garbanzos and vice versa. Although both S. sclerotiorum and S. trifoliorum have been confirmed on alfalfa, mostly S. trifoliorum has been identified on garbanzos.
Both Ascochyta and Sclerotinia can be transmitted by aerial spores, and for such infections, fungicides are available for control in garbanzos, although classes of materials should be rotated to avoid resistance.
She also noted that Sclerotinia occurs in blackeyes, although she has seen it only rarely in that crop, probably because of the high temperatures in the southern SJV during the blackeye growing season.
“It's probably not a good idea to plant blackeyes and garbanzos back-to-back because of Rhizoctonia and other problems, but considering the high temperatures, it's not a completely bad idea,” Frate said.
In general, she added, it is not wise to follow legumes with legumes for an extended period, although it may work for one or two years.