was apparent on both Cal 7 and DSL by mid-season of 1960. But Cal 7 gave a Tarweed higher lint yield than A4-42 and the DSL yield was below that of A4-42. The 1961 planting was made on a field where an a nuisance on ranges observational block of DSL was grown in 1960. Following the wilted cotton of 1960, it was easy to detect wilt symptoms S. S. WINANS ’ C. M. MCKELL in mid-summer throughout the Ca17 and DSL plots, and minor symptoms were evi- dent even in A4-42 plots. Yields from this forms dense patches among and above location were considerably lower for all the dry annual forage species-obscuring varieties in 1961 than in 1960. Never- and limiting use of desirable species as theless, the grower allowed the test to dry feed by livestock. remain on the same plots in 1962. Some observations of tarweed seed However, the grower did switch the production, germination, and hard seed planting scheme from “solid” cotton to percentage were made to help show how “2-in, 2-out.” Significant yield differ- tarweed persists even though a seed crop ences were obtained among the varieties might fail to mature. Clipping and fall in 1962. A442 was outstanding for its application of nitrogen were studied as wilt tolerance even though the low sum- possible means of minimizing tarweed mer temperatures in 1962 were ideal for stands during the seedling stage. the wilt organism to operate. Heavy wilt Three tarweed-infested rangeland areas damage was evident in the Ca17 plots and located in the foothills in lint yield was 19% lower than A4-42, as Sacramento, Tuolumne, and Madera shown in the graph. DSL was severely counties were chosen in the fall of 1956 damaged by Verticillium wilt. In fact, the as study sites. An additional study of ni- wilt attacks occurred so early in the sum- Tarweed seedling ( virgata) as it trogen fertilization was initiated in the mer that the “2-in, 2-out” planting scheme appears in early annual range forage. fall of 1958 and carried on through 1960 offered no advantage. With both the di- at the Shaubach Ranch, Madera County. Old tarweed from the previous rect wilt damage and the indirect loss of Tarweed is well adapted for survival as a growing season were used as a basis to growth advantage due to the earliness of nuisance plant on California ranges. While the wilt attack, the yield of DSL was 5770 choose specific sites for these studies. expensive control measures may not be lower than that of A4-42. Tarweed seeds were harvested by hand justified, effective methods are needed for in the fall from mature plants growing Woodville minimizing the use of soil’ moisture by tar- on a foothill range area in Madera It was necessary to relocate the test weed seedlngs in the spring. Clipping or County. Seeds were germinated for 28 plots at Woodville with a different grower heavy grazing and nitrogen fertilization days with temperatures alternating from each year since farm units are smaller offer possibilities for reduction in density 5, 15, 20, and 2O-3O0C. and the growers cannot afford to absorb of tarweed seedlings in favor of the more Treatments the loss from Verticillium wilt continu- desirable forage species. A series of 10x20 ft. plots were ously. clipped at three-week intervals through Verticillium wilt was evident by mid- ARWEED, Holocarpha virgata (A. the spring months. A different set of plots season on both Cal 7 and DSL in 1960 Gray, Keck) , is a nuisance plant that was clipped at a height of 1% inches and 1961. The land used in 1962 gave growsT on California foothill rangelands with a scythette mower at each location less wilt damage. Data for the three years, and is generally distributed in the Sierra each time. Tarweed density estimates as shown in the graph, shows higher foothills, Central Valley and inner coast were made on June 27, 1957. Soil mois- yields were obtained from A4-42. The ranges. At times it dominates some of ture percentage was determined at 5 to 7- growth of both Cal 7 and DSL’was visi- the better forage-producing sites. This inch and 18 to 20-inch depths. bly reduced on the 1960 and 1961 plots annual forb germinates in the fall, but Fertilized plots, .2 acre in size, were as a result of wilt attacks. The Woodville has its greatest growth in the late spring established at each county location in area plots showed a more drastic yield re- and summer. The tarweed stand is per- 1957. Treatments consisted of 60, 120, duction for Ca17 than at any of the three sistent but may be dominant one year and 180 pounds of nitrogen applied as other areas. and of only minor proportions in a fol- 16-20-0 for comparison with an unferti- Merrill Lehman is Assistant Agrono- lowing year. Grazing use of tarweed has lized check plot. A strip through each plot mist; R. J. Miravalle is Geneticist; and been observed during winter and early was harvested June 27, 1958, with a John H. Turner is Agronomist-in-Charge, spring. Tarweed growth is most rapid in scythette mower. The percentage of tar- CRD, Agricultural Research Service, the late spring when the plants compete weed was obtained by hand separation. USDA Cotton Research Station, Shafter. with desirable forage species for the At the Shaubach Ranch the rates of Miravalle and Turner are also Research diminishing soil moisture. Tarweed be- nitrogen applied were 0, 40, 80, 120, and Associates in the Agricultural Experi- comes most noticeable and particularly 160 pounds per acre using 16-20-0. Fer- ment Station, Department of Agronomy, objectionable in the summer season when tilizer treatments were replicated four University of California, Davis. its bushy-stemmed, ill-scented growth times using 20x20-ft. plots. The total plot

CALIFORNIA AGRICULTURE, APRIL, 1963 11 TABLE 1. MEAN SEED GERMINATION AND HARD SEED TABLE 2. RESULTS OF CLIPPING ON TARWEED none at the other. In April all forage PERCENTAGE OF TARWEED DENSITY ON JUNE* 27 AT THREE FIELD LOCATIONS plants were growing rapidly and tarweed Germination* Time of Sacramento Tuolumne Modero Hord Seed foroge plants per plonts per plonts per seedlings were from 4 to 6 inches in Ya (%I (C) 14 days 28 days removal sq. ft. sq. ft. sq. ft. height. In contrast, soft chess was 8 to 14 5" 1 1 89 March 6 ...... 18.5 3.5 8.9 inches tall, and in the early flowering 15" 2 2 94 March 27 ...... 14.8 6.3 17.2 20" 2 3 84 April 15 . .._.._4.4 4.5 6.9 stage. Clipping during the final weeks of 20-30" 0 3 90 May 10 ...... 0.7 2.5 4.5 the spring growing season substantially *Germination tests by Seed Laboratory, State of June 10 ____....0.0 0.0 8.9 reduced the density of tarweed. California Deportment of Agriculture. Non-cbped . . . . 14.2 4.4 12.6 'Meon of three replications. Plots clipped on May 10 when tarweed seedling height was from four to sixteen area was fenced during winter and inches had 95% less tarweed than non- spring, but dry feed was removed by to produce fifty to several hundred yel- clipped plots at Sacramento, 43% less at grazing during the summer. The plot area low-flowered, composite-type heads. Four Sonora, and 64% less at Madera. Tar- was again fenced the second growing sea- or five glistening black seeds, 1 mm in weed density was reduced to zero at both son following fertilization. Moisture de- diameter, are usually produced in each Sacramento and Tuolumne locations pletion was recorded for 12-inch and 36- seed head. Maximum seed germination when clipped in early June just after inch soil depths by using gypsum electri- was 1% to 3% for one-year-old seed, forage maturity. In the Madera plots, tar- cal-resistance blocks. Following fertilizer regardless of temperature (table 1). No weed density increased after forage ma- application in the second year, forage differences resulted from an additional turity, probably because of a late rain. yield, tarweed density and tarweed height 14 days in the seed germinator. Hard Forage composition were recorded from all treatments near seed content ranged from 84% to 94% forage maturity. Three random square- under all temperature conditions. Species composition of forage one year foot samples were harvested and oven- Results from time of clipping varied later, in each location, appeared to be dryed from each plot. The number of from no reduction to almost complete re- unaffected by the clipping treatments ex- tarweed plants per square foot was duction of the current stand of tarweed cept on plots clipped late in the previous counted and measured for height. Plant (table 2). Early clipping generally re- growing season. On these plots, bur clo\er material from one replication was hand- sulted in an increase in the number of appeared to replace soft chess in domi- separated by forage class to determine tarweed plants present in June as com- nance. species composition. pared to unclipped plots. In March, tar- The effectiveness of clipping tarweed weed seedlings were small, averaging l?hz in the late spring is attributed to the in- Seed yield inches tall, and the two major forage creased height of tarweed and limited Tarweed seed yield per plant is high, species, soft chess and broadleaf filaree, availability of soil moisture. In March hut the seed germination percenatge is averaged 43" inches in height. Clipping very few tarweed seedlings were clipped low with a large proportion of hard seed in mid-April reduced tarweed density, below any lateral growing points. Early remaining. Mature plants range in height and resulted in a 45% to 69% reduction clipping appeared to reduce competition from 6 inches to 3 feet, and are estimated of tarweed plants at two locations but from other plants and favor tarweed growth. In early April growing condi- tions were still favorable for the rapid recovery of winter annuals after clipping, A stand of maturing tarweed in mid-summer as it limits the production and use of dry annual range forage. thus providing plant competition and suf- ficient time for maximum use of remain- ing spring moisture. In late spring the height of tarweed plants results in clip- ping below lateral growing points. Reduction of tarweed may also occur following nitrogen application, but fer- tilizer carry-over to a succeeding year appears to have little effect on the amount of tarweed. The volume of tarweed growth was reduced as forage production increased with each increment of applied nitrogen at each location (table 3). Tar-

TABLE 3. TARWEED PERCENTAGE AND FORAGE YIELD FROM UNFERTILIZED AND FERTILIZED RANGE SITES'

Socromento Tuolumne Modero N ferti- lization For- Tor- For- Tor- For- Tor- rate oge weed age weed age weed Ibs/A % Ibs/A Oh Ibs/A Oh Check..2,084 9.4 2,141 9.0 934 1.1 Neo.. . . .2,709 5.1 2,253 1.5 1,427 0.4 Nim ... .3,650 1.3 1,058 2.5 1,852 0.1 Nian 3,251 0.7 2,586 4.3 1,747 0.0 "Yields based on .OOl-acre strip harvested ond oven dried. Tarweed percentage by hand seporation from total yield. weed on unfertilized check areas varied VARIETY IMPROVEMENT OF RICE from 1% of the total forage produced at Madera to 9% at Sacramento and Tu- DURINGTHE PAST two years, rice variety To create a wider basis of long-grain olumne. improvement work at the Rice Experi- hybrid-material-and to incorporate the Locaticns with the highest tarweed ment Station, Biggs, has been carried out good characteristics of Colusa with stiff percentages were also highest in forage on a larger scale with increased attention straw45 crosses were made in 1961. yield on the unfertilized treatments. Ap- given to the development of non-lodging These involved 20 varieties from Suri- plication of 60 pounds of nitrogen per short, medium and long-grain varieties nam, most of which have stiff straw, acre generally reduced the tarweed at with desired cooking qualities. very large grains and also good cooking Sacramento and Madera by 50%. Fur- Varieties developed here in former quality. They were crossed with Calif. ther reductions of 87% were recorded years and introductions from several 405A and Belle Patna (both early gla- with the application of 120 pounds of ni- countries were screened; some 24 were brous long-grain types) and with Colusa trogen per acre and 99% with 180 tested in large replicated yield trials. (short-grain). By growing the F, in the pounds. Results at Sonora were not as Four short-grain varieties yielded better greenhouse during the winter of 1961 the consistent as the other two locations; and than Caloro and lodged less. One long- F, could be sown in the field during the the greatest reduction in tarweed, 82% grain variety originating from the South summer of 1962. of the check, was recorded for the treat- produced almost as much as Caloro; had Several crosses, including those with ment with 60 pounds of nitrogen per acre. a maturity period of from 110 to 125 Colusa, showed considerable stiff straw in days, depending on the method and date the F, plants. As expected, the crosses Soil moisture of seeding; and good cooking qualities. between the American and Surinam long- Soil moisture measurements on plots in In 1961, some 1,000 selections were grain varieties produced seed of a very Sacramento County show a pattern of made from two hybrid-populations re- good type, and several combinations were decreasing moisture availability on un- ceived in the F, and F, generations from as early as Colusa. Thousand-grain fertilized and fertilized range plots dur- Beaumont, Texas. From these, 55 promis- weights were estimated up to 38 grams. ing the critical period of April to mid- ing lines were retained in 1962 and, It is expected that a number of desirable May. By the middle of May, soil moisture under drilled conditions, they did not lines can be obtained within three genera- on unfertilized plots decreased from 12% lodge. Most of these 55 lines have a very tions.-John J. Mastenbroek, Associate to 8% at the 6-inch depth and from 23% good grain-type and a 1,000-grain weight in the Experiment Station, Agronomy to 15% at the 20-inch depth. In compari- ranging from 28 to 33 grams. Dept., Rice Experiment Station, Riggs. son, moisture percentage on fertilized plots decreased from 9% to 5% at the 6-inch depth and at 20 inches remained at approximately 15%. It appears that grass 25% on unfertilized treatments. In species which mature just as tarweed be- less soil moisture is available for tarweed contrast, filaree averaged 90% and grass gins its rapid growth in late spring. In use on fertilized plots at its critical period 3% on fertilized treatments. If increased the year following fertilization there may in competition with the more desirable yield differences are slight, tarweed seed- or may not be any reduction of tarweed forage species. The greater forage yields lings may not be subject to the severe density depending on the amount of fer- indicate that soil moisture is more effec- competition for space and moisture which tilizer carry-over. tively utilized on the fertilized than on limit growth in the initial year of fer- the unfertilized plots. tilization. S. S. Winans is Laboratory Technzcian, Hopland Field Station, and C. M. McKell Carryover Well adapted is Assistant Agronomist, Agronomy De- At the Shaubach Ranch, the carry-over Tarweed appears to be well adapted to partment, University of California, Agri- of fertilizer to the succeeding year continue as a nuisance plant on Califor- cultural Experiment Station, Riverside slightly increased forage yield, but tar- nia ranges. Habits of late spring and sum- (formerly Plant Physiologist, Crops Re- weed density and the proportion of tar- mer growth, apparent drought tolerance, search Division, ARS, USDA). weed to other plants remained nearly con- high capacity for seed production, growth Investigations reported here were in stant on both unfertilized and fertilized in dense stands, and a very high hard cooperation with the Crops Research Di- plots. Average forage yield on unfertilized seed percentage help to explain tarweed vision, ARS, USDA, and the University plots was 2,230 pounds per acre, as com- persistence and pose problems in its con- of California Agricultural Experiment pared with 2,888 pounds per acre on the t rol . Station. The Madera field plot at the Sun fertilized carry-over treatments. Al- Expensive control measures may not Joaquin Experimental Range was made though forage production was 30% be justified. However, effective ways to available through the cooperation of the greater on carry-over fertilized treat- minimize use of soil moisture by tarweed Pacific Southwest Forest and Range Ex- ments, tarweed seedling density was seedlings in the spring growing period periment Station, U. S. Forest Service. nearly equal with 5.3 plants per square are needed, especially if spring forage is Harry S. Hinkley, Farm Advisor, Tu- foot on unfertilized and 6.0 plants on fer- to be managed for use as dry summer olumne County, and James T. Elings, tilized plots. feed. Clipping in the late spring or inten- Farm Advisor, Sacramento County (now The proportion of tarweed to other sified grazing in mid-spring should bring Extension Animal Husbandry Specialist, plants, on a weight basis, averaged 3% about a reduction of tarweed seedlings University of California, Davis), assisted on unfertilized check plots and 2% on and favor the more desirable species. Fer- with field work on this project. Enos fertilized treatments with other forage tilization with nitrogen may also reduce Shaubach, Coarsegold rancher, Madera components differing more than tarweed. the density of tarweed by increasing the County, also made field plots and ranch Broadleaf filaree averaged 71% and vigor and moisture use by competing facilities available for this study.

CALIFORNIA AGRICULTURE, APRIL, 1963 13