UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA Effect of Extending the Cutting Season on the Yield of Asparagus H. A.JONES BULLETIN 535 July, 1932 UNIVERSITY OF CALIFORNIA PRINTING OFFICE BERKELEY, CALIFORNIA Digitized by the Internet Archive in 2012 with funding from University of California, Davis Libraries http://www.archive.org/details/effectofextendin535jone EFFECT OF EXTENDING THE CUTTING SEASON ON THE YIELD OF ASPARAGUS 1 H. A. JONES* During recent years many asparagus growers of California, espe- cially those in the Delta region, have been asking whether the long season over which they harvest asparagus has any effect on production of the beds. Experiments were therefore begun at Davis in 1924 to determine what effect lengthening the cutting season would have on the longevity of asparagus beds, on the size of spears, and on the total yield per acre. Although the tests will probably be continued for another six or seven years, certain results already obtained are of considerable practical interest and may well be reported at this time. The variety used for these studies was Palmetto, and the crowns were grown in a nursery at the University Farm in 1923. They were dug in February, 1924, and within a few days were set in furrows 8 inches deep, 7% feet apart, and 236% feet long, the crowns being spaced 2 feet apart in the row. The tests were conducted with both male and female plants, not intermingled, but planted in separate rows side by side. The plots are in duplicate, one row in each plot. In this bulletin the data for the male and female plants have been analyzed separately. During the summer the field was surface-irrigated whenever neces- sary. The time of the first irrigation varied somewhat with the amount of winter rainfall. A heavy irrigation was always given immediately after the cutting season, and the last application was usually made about the first of September. The tops were cut, as a rule, about the middle of October, allowed to dry, and burned. Each fall, about 15 tons of barnyard manure was applied per acre and then plowed or disked under. Ridges of soil were thrown over the rows with a disk to facilitate rotting of the stubble during the winter, and were left until the field was prepared for the harvesting season. Then they were disked down and low ones rebuilt to mark the rows for the cutters and to facilitate irrigation. 1 Received for publication May 27, 1932. 2 Professor of Truck Crops and Olericulturist in the Experiment Station. 4 University of California — Experiment Station In this bulletin only two different lengths of cutting season are com- pared. About May 20 is considered to be the end of the normal cutting season at Davis for a bed that is in full bearing. After about this time, the spears branch while still very short and become increasingly tough and woody. This deterioration in quality late in the season may result from a number of factors, one of the most important of which is probably the lowering of the reserve foods stored in the roots. What is considered the normal cutting season at Davis may not be the normal cutting season for other districts in the state. In areas where the temperature is cooler, one would expect a somewhat longer cutting season ; and in districts that warm rapidly in the spring and have warm days and nights, one would expect the cutting season to be somewhat shorter. THE PRODUCTION OF SPEARS For convenience, the normal-cutting-season plots will, hereafter, be designated as " A " ; and those cut for the longer period of time will be designated as "B." The A plots were not cut the year after planting, whereas the B plots were cut at that time. Jones and Robbins 3 have previously shown that if asparagus makes a good growth the year it is planted, it may be cut with advantage for a short time the following year for cutting early in the year helps to prevent rust infestation ; also as a rule the price is good early in the season and cutting helps to defray expenses during the early life of the bed. In each year except 1925 and 1926, the B plots have been cut about two weeks longer than the A plots. The dates on which the last cuttings were made each year are given in table 1. TABLE 1 Dates on Which Last Cuttings Were Made Plots 1925 1926 1927 1928 1929 1930 1931 A (normal cutting season) B (long cutting season) Not cut April 1 April 25 May 20 May 15 May 31 May 15 May 31 May 20 June 3 May 20 June 3 May 20 June 3 From year to year, the date of the first cutting varied somewhat with climatic conditions ; but it was, as a rule, in late February or early March. The plots were usually harvested once each day through- s Jones, H. A., and W. W. Bobbins. Influence of cutting asparagus the first year after planting on production the following year. Proc. Amer. Soc. Hort. Sci. 23:23-25. 1926. Bul. 535] Effect of Extending Cutting Season on Asparagus 5 out the cutting season. Late in the season it was sometimes necessary to cut the B plots twice a day because the spears started to branch while still comparatively short and soon became unmarketable, but this procedure was never necessary until the A plots had been laid by. The spears cut were always iy^ inches or more above the ground, and all were cut long enough to be trimmed to a uniform length of 8V2 inches. Immediately after being harvested they were counted, trimmed, and weighed, so that all yield records in the following tables are for spears cut green and trimmed to a length of 8V2 inches. Spears too spindling to be included in the usual small grade of the fresh pack were cut and left lying in the field. Average Number of Spears Produced per Plant. — The average number of spears produced per plant, given in table 2, shows that for both sexes the number of spears increased from year to year but that more spears were always produced by the B plots. TABLE 2 Average Number of Spears per Plant Plots 1925 1926 1927 1928 1929 1930 1931 Male plants A 2.74 16.91 28.75 25.16 33.71 30.19 40.51 39.75 51.37 44.87 60.15 62.10 B 74.12 Female plants A 1.79 8.88 14.66 15.32 18.96 19.51 23.52 24.08 29.72 30.76 36.65 43.46 B 50.91 For the years 1926 to 1931, the male plants of the B plots pro- duced an average of 11.61 spears per year more than those of the A plots (column 3 of table 12) ; and the female plants of the B plots produced 5.40 spears per year more than those of the A plots. Average Weight of Spears. — The average weight per spear for both male and female plants, given in table 3, shows that the spears of the A plots were consistently heavier than those of the B plots. According to the data in column 4, table 12, the male spears of the A plots weighed 1.95 grams per spear more than those of the B plots; and the female spears of the A plots weighed 4.93 grams per spear more than those of the B plots. University of California — Experiment Station TABLE 3 Average Weight of Spears in Grams Plots 1925 1926 1927 1928 1929 1930 1931 Male plants A 17.55 21.87 21.34 24.19 21.60 24.00 20.63 23.24 22.76 22.70 20.80 23.70 B 20.87 Female plants A 18.25 26 50 23.61 30.82 27.68 32.98 26.59 36.62 3012 32.07 27.00 31.88 B 26.29 Size Grades. — Each day throughout the cutting season during the three years 1929 to 1931, the spears were graded to determine the distribution of sizes. The device shown in figure 1 was used in Fig. 1. — A simple device used to grade asparagus spears for size. The diameters of the openings are %, %, %, and % inch. grading. The five grades used and the percentage of spears by weight that fall into the different size grades are given in table 4. The data for the same size grade for the A and B plots are placed in parallel columns for ease of comparison. From 1929 to 1931 there was a definite increase in the percentage of the smaller grades, with a corresponding decrease in the larger grades. This increase in the percentage of the smaller grades occurred in both the A and B plots, but was much more rapid in the latter. The data in table 4 give only the percentages of spears by weight that fall into the different size grades. The important practical con- sideration is the yield per acre of the various grades; these figures are given in table 5. Certain grades, especially those under y 2 inch, show a much more rapid increase than would be expected from the Bul. 535] Effect of Extending Cutting Seasqn on Asparagus 7 TABLE 4 Percentages of Spears by Weight Occurring in the Different Size Grades Year Under % inch % to Yi inch to Y% inch Y% to \i inch Over % inch Male plants 1929 6.59 9.82 27.58 31.99 39.11 35 11 22.24 19.95 4.48 3 12 1930 7.65 13.02 37.81 42.45 35.37 30 37 15.98 12.43 3.19 1.74 1931 11.62 20.24 41.06 45.09 32.22 25.99 13.27 7.59 1.83 1.09 Female plants 1929 1 32 3.40 9 40 19.15 29.46 35 08 40.33 31.55 19.48 10.82 1930 2.08 5.23 17.84 28.68 34.82 35.46 33.44 24.76 11.82 5.87 1931 4 33 9.47 24.12 35.75 35.33 34.43 27.03 17.16 9.19 3.18 TABLE 5 Weight of Spears in Pounds per Acre Occurring in the Different Size Grades Plots Year Under % inch ^toH inch i to y % inch inch Male plants Over% inch Total f 1929 \ 1930 [ 1931 f 1929 1930 1931 384 498 730 ,037 1,608 2,459 3,855 2,380 3,383 4,439 2,280 2,300 3,026 2,612 2,420 2,559 1,297 1,039 1,246 1,484 991 747 261 5,830 207 6,503 172 9,390 232 7,438 139 7,970 107 9,845 Female plants A f 1929 \ 1930 [ 1931 f 1929 \ 1930 [ 1931 74 125 382 194 329 806 524 1,069 2,130 1,090 1,806 3,043 1,642 2,086 3,120 1,997 2,232 2,931 2,248 2,003 2,387 1,796 1,559 1,461 1,086 708 812 616 370 271 5,574 5,991 B 8,831 5,693 6,296 8,512 8 University of California — Experiment Station increase in percentage. The explanation is that the yield per acre increases as well as the percentage. The yield per acre of the large grades, especially those above % inch, is greatly reduced in the B plots. TABLE 6 Percentages of Spears by Weight in Male Plants Occurring in the Different Size Grades, 1930 Periods Under % A inch % to Yi inch I ViloYi inch Y % to M inch Over s /i inch Feb. 17 to March 16 Marcn 17 to 25 March 26 to April 2... April 3 to 10 April 11 to 18 April 19 to 26 April 27 to May 4 May 5 to 12 May 13 to 20 May 21 to 28 May 29 to June 3 .... 2.4 5.1 4 4.5 6.1 8.0 10.8 12.0 16.9 27.0 21.7 26.6 19.5 28.5 25.7 29.9 34.0 42.2 50.2 51.2 54.7 42.9 37.5 32.7 33 4 36.1 40.7 49.8 52 3 50.1 57.7 49.6 50.0 43.9 40.1 37.1 35 38.6 31.2 28.4 22.5 32.4 35 4 37.7 34 5 35.9 37.8 26.2 25.8 20.1 17.6 18.8 23 19.6 23.6 23.9 20.4 9.8 7 8.0 5.3 16 3 17.3 20 1 23.7 16.4 10 6 2 5.1 2.5 2.8 5 0.0 2.5 3.3 2.8 3.1 1.1 10 0.7 4 2 TABLE 7 Percentages of Spears by Weight in the Female Plants Occurring in the Different Size Grades, 1930 Periods Under % inch y^ioVi inch Y% to V* inch Y% to % inch Over % inch Feb. 17 to March March 17 to 25 March 26 to April 2 April 3 to 10 April 11 to 18 April 19 to 26 April 26 to May 4.. May 5 to 12 May 13 to 20 May 21 to 28 May 29 to June 3 0.6 1.3 1.2 1.0 16 1.6 2.3 3 3 5.8 2.0 2.1 2.6 2.5 3.4 7.8 11 1 9.0 8.3 10.5 9.2 9.2 12.5 17.8 25.2 30 37.3 17.3 19.6 16.4 17.2 18.5 26.3 32.3 40 8 41.6 47.6 39.3 35.5 34.5 32.3 29.3 32.2 41.1 38.5 38.0 35.3 37.1 35.2 35.8 33.6 36.7 40.9 36.6 35.5 33 31 3 34 .2 38.0 42 3 40.9 42.2 39 3 30.1 26.2 22.8 18.2 45.7 34.2 35.8 37.4 30 4 23.7 22 9 13 13 11.2 15.0 17.6 11.5 16.4 18.3 14.4 9.4 7.7 6 34 0.0 9.0 9 9 9.2 11 9 5 7 2.2 2.9 1.3 9 1.7 In tables 6 to 9 the size grades are given for plots A and B, and for both males and females. The data for 8-day periods have been averaged together, except for the first and last periods, These data show that for both males and females the percentages of the small grades are higher in the B plots than in the A, throughout the entire harvest- Bul. 535] Effect of Extending Cutting Season on Asparagus 9 ing season. There is also a definite but rather irregular increase in the percentages of the smaller grades and a decrease in the larger grades as the cutting season advances. TABLE 8 Percentages of Spears by Weight in the Male Plants Occurring in the Different Size Grades, 1931 Periods Under % inch V*toy> inch U to V* inch b Ato% inch Over % inch March 3 to 16 March 17 to 25 March 26 to April 2 April 3 to 10 April 11 to 18 April 19 to 26 April 27 to May 4.. May 5 to 12 May 13 to 20 May 21 to 28 May 29 to June 3. 9.6 5.3 4.7 8.5 11.6 13.3 15.2 15.2 22.7 15.0 13.2 10.4 15.1 19.3 16.2 25.0 24.3 27.6 34.0 27.2 41.1 45.6 43.8 45.5 34.0 39.0 39.1 41.1 39.2 52.4 48.9 52.0 48.2 45.1 46.3 40.2 42.6 44.9 36.5 40.0 32.8 37.6 37.3 28.7 33.9 28.4 31.7 32 3 27.6 19.1 29.3 31.4 27.9 23.1 28.7 25.0 23.4 20.8 23.9 24 2 10 19 1.9 1.3 4.3 2.9 0.8 0.4 0.0 19 6 0.4 1.5 1.2 14 2.9 0.8 1 2 TABLE 9 Percentages of Spears by Weight in the Female Plants Occurring in the Different Size Grades, 1931 Periods Under % inch % to K inch to 5 A inch Y% to % inch Over % inch March 4 to 16 March 17 to 25 March 26 to April 2 April 3 to 10 April 11 to 18 April 19 to 26 April 27 to May 4.. May 5 to 12 May 13 to 20 May 21 to 28 May 29 to June 3 2.1 4.7 1.1 2.3 2.9 4.5 4.9 6.0 9.6 8.3 4.7 2.6 4.7 9.0 8.8 12 1 10 9 13.6 16 9 14.4 12.1 21.7 20.4 22.1 22.7 24.4 23.9 29.1 30.0 46.0 33.9 36 6 34 5 36.6 35. 32. 38. 39 33 33 41.5 43.8 37.7 30.9 45.1 43.3 35.4 30.9 31.6 315 32.8 31.6 33.8 30.6 39.7 25.4 29.8 14.8 12.8 15.9 22.7 19.9 19.0 19.7 14 4 12.6 14 3 14.4 13.0 6.7 4.9 10 4 12.1 11.1 11.4 8.8 6.1 0.0 3.6 1.5 Average Weight of Spears Produced per Plant. — Table 10 gives the average yield of spears produced per plant. In all plots of both males and females, the yield increased from year to year. The data in column 5 of table 12 show that the yield of the male plants in the B plots was significantly higher than that of the A plots. In the female plants, however, no significant difference appeared between 10 University of California — Experiment Station the A and B plots. The long cutting- season seems, therefore, to be more harmful to the female than to the male plants. TABLE 10 Average Yield of Spears per Plant, in Grams Plots 1925 1926 1927 1928 1929 1930 1931 Male plants A B 47 369 613 607 728 724 836 913 1,169 1,018 1,252 1,470 1,547 Female plants A 33 236 345 473 524 645 624 878 895 943 989 1,390 B 1,338 Average Yield of Spears per Acre. — The average yield of spears per acre, given in table 11, shows an increase from year to year in all the plots. The data in column 6 of table 12 show that for the male plants the B plots are significantly higher-yielding than the A plots. Although the B plots outyield the A plots in total yield per TABLE 11 Average Yield of Spears per Acre, in Pounds Plots 1925 1926 1927 1928 1929 1930 1931 Male plants A B 301 2,355 3,898 3,876 4,631 4,625 5,319 5,831 7,439 6,504 7,969 9,391 9,845 Female plants A B 208 1,498 2,193 2,998 3,330 4,089 3,974 5,574 5,692 5,991 6,296 8,831 8,513 acre, the data in table 5 show that the difference is mainly in the smaller grades, and that the A plots actually outyield the B plots in the larger grades. In the female plants, no significant difference in yield per acre appears between the A and B plots; but here again the longer cutting season reduces considerably the yield per acre of the two largest grades. Bul. 535] Effect of Extending Cutting Season on Asparagus 11 TABLE 12 Comparison of Asparagus Plants Cut Different Lengths of Time for the Years 1926-1931* Sex Plots compared Difference in number of spears per plant Difference in weight of single spear (grams) Difference in weight of spears per plant (grams) Difference in yield per acre (pounds) 1 * B - A B - A 3 11.61* 5.40* 4 -1.95* -4.93* 5 174* 25 1 6 1,087* Female 170t * Differences are considered significant. t Differences are not considered significant. THE PRODUCTION OF STALKS In addition to a record of spear production from the A and B plots, a record was kept of the number and weight of stalks produced. Each year the stalks were counted, cut, and weighed before the first killing frost. The stalks were always weighed immediately after cutting, and all the different plots were weighed and cut the same day. Although they could not be harvested at the same stage of maturity from year to year, an attempt was made to weigh them while they were still green and before the foliage began to fall. Average Number of Stalks Produced per Plant. — The average num- ber of stalks produced per plant is given in table 13. The number varied considerably but showed a gradual increase from year to year. More stalks were produced by the males than by the females, but there was no significant difference between the A and B plots of either sex (column 3, table 17). Average Weight per Stalk. — The average weight per stalk for the different sexes and for the A and B plots given in table 14 shows that there was considerable difference from year to year, but in the case of both male and female plants the stalks from the B plots were significantly lighter (column 4, table 17). 4 The data in tables 12 and 17 are the result of analysis using Love 's 5 modifi- cation of Student's method to determine whether the differences obtained are significant. In column 3 of the above table, 11.61 is obtained by subtracting the number of spears per plant of the A plants from those of the B. The number is positive and means that, on an average, 11.61 more spears per plant were pro- duced each year in the B plots. In column 4 negative numbers were obtained. This means that average weight of the spears from the B plots was smaller than that of those from the A plots. 5 Love, H. H. A modification of Student's table for use in interpreting experimental results. Jour. Amer. Soc. Agron. 16:68-73. 1924. 12 University of California — Experiment Station TABLE 13 Average Number of Stalks Produced per Plant Plots 1925 1926 1927 1928 1929 1930 1931 Male plants A B 8.86 10.24 9.71 9.51 9.87 8.38 13.20 16.47 18.07 16.09 13.45 16.72 18 91 20 70 Female plants A B 5.81 5.67 5.12 5.48 7.28 6.80 8.68 9.98 10.39 10.30 10.59 11.85 13.80 13.79 TABLE 14 Average Weight per Stalk, in Pounds Plots 1925 1926 1927 1928 1929 1930 Male plants A B 0.306 0.284 0.322 0264 0.368 0.326 0286 0.161 0.281 0.256 396 225 Female plants A B 0.394 0.381 0.512 328 0.422 266 421 0.359 0.553 0.421 0.549 0.247 TABLE 15 Average Weight op Stalks Produced per Plant, in Pounds Plots 1924 1925 1926 1927 1928 1929 1930 Male plants A 0.75 2 70 3.10 3.54 3.83 5 07 5.32 B 0.74 2.89 2 50 2 70 2.65 4.12 3.73 Female plants A B 0.66 0.66 2.28 2 15 2 47 1.74 3.08 1.79 3.67 3 58 5.78 4 37 5.82 2.93 Bul. 535] Effect of Extending Cutting Season on Asparagus 13 Average Weight of Stalks Produced per Plant. — The average weight of stalks per plant, given in table 15, shows a rather irregular increase from year to year. The data in column 5 of table 17 indicate that the weight of stalks is significantly heavier in the A plots for both the male and female plants. One of the chief disadvantages of a long cutting season is the shortening of the period during which food is elaborated. Not only is there less time for the manufacture of food for storage, but there is much less weight of plant to elaborate food. The weight of stalks per plant from the B plots was consistently lower after 1924 in the female plants and after 1925 in the male Fig. 2. — The plots on the left which have just been disked were cut the last time for the season on June 3, 1930. The two rows on the right were last cut on May 20. The photograph, taken on June 4, shows the amount of growth made by the A plots before the B plots were laid by. plants. The drain on the reserve food in the B plots probably accounts for the small growth made after the cutting season. The stalks of the B plots branch lower and do not grow so high as the stalks of the A plots. The difference in the type of growth after the cutting season can be seen by referring to figures 2 and 3. Figure 2 shows the growth made in one of the A plots 15 days after being laid by, and figure 3 shows the growth made in one of the B plots 15 days after being laid by. In 1931 the commercial cutting season for the canning crop was shortened because of the large carryover of the asparagus pack. Most of the beds in the Delta were laid by about the last of May, which is approximately a month earlier than usual. It was very noticeable that the top growth that year was considerably heavier than usual. 14 University of California — Experiment Station Fig. 3. — The A plots on the right were laid by on May 20, and the B plots on the left, shown by the young growth, were last cut on June 3. The A plots had been laid by for 29 days and the B plots for 15 days when the photograph was taken on June 18, 1931. Average Weight of Stalks per Acre. — The average weight of stalks per acre, given in table 16, shows that there was a gradual but rather irregular increase from year to year— an increase much more irregular TABLE 16 Average Weight of Stalks Produced per Acre, in Pounds Plots 1924 1925 1926 1927 1928 1929 1930 Male plants A B 2,173 2,137 7,834 8,337 8,976 7,208 10,241 7,797 10,941 7,625 14,686 11,886 15,422 10,744 Female plants A B 1,891 1,891 6,569 6,201 7,110 5,022 8,865 5,174 10,600 10,351 16,663 12,635 16,736 8,436 in the B plots than in the A, of both the males and the females. The data in column 6 of table 17 show that the A plots produced a significantly heavier yield of stalks than the B. Bul. 535] Effect of Extending Cutting Season on Asparagus 15 TABLE 17 Comparison of Asparagus Plants Cut Different Lengths of Time Sex Plots compared Difference in number of stalks per plant Difference in weight of single stalks (pounds) Difference in weight of stalks per plant(pounds) Difference in yield per acre (pounds) / Male Female 2 B - A B - A 3 0.86t 0.31t 4 -0.111* -0.158* 5 -0.71* -0 93* 6 -2,077* -2,675* * Differences are considered significant, t Differences are not considered significant. SUMMARY Production of Spears. — The number of spears produced per plant increased from year to year in both the A and B plots. Because of the longer cutting" season, the B plots produced more spears per plant than the A plots. The average weight per spear was always heavier in the A plots. The size grades show that the B plots produced the highest percentage of small spears and that this difference usually holds throughout the cutting season. The yield of spears produced per plant increased from year to year in both the A and B plots. In the males, the yield of the B plots was significantly higher than that of the A. In the females there was no significant difference in yield between A and B plots. The yield of spears per acre increased from year to year in both the A and B plots. In the males the yield of the B plots was signifi- cantly higher than that of the A. In the females there was no significant difference in yield between the A and B plots. In both sexes the highest yield of the two largest grades was secured from the A plots. Production of Stalks. — There was a gradual but rather irregular increase in the number of stalks produced per plant from year to year, but no significant difference between the A and B plots. The average weight per stalk of the A plots was significantly heavier than that of the B. The average weight of stalks produced per plant was significantly heavier in the A than in the B plots. The average weight of stalks produced per acre was significantly heavier in the A than in the B plots.