Comparing Organic and Conventional Fertilization Methods for Cut Flower Production in Haygrove High Tunnels

Organic versus Conventional Fertilization of Lisianthus

Based on nearly all growth parameters measured on experiment day 81, all conventional slow release rates, the low organic slow release fertilizer and the low and moderate rates of both soluble fertilizers resulted in similar growth. The only exception is that the low rate of organic slow release fertilizer did not perform as well as the others listed above based on leaf length.

The optimum media EC for lisianthus production has been reported as 1.0 to 1.2 mmhos.cm-1 (Gill et al., 2000; PanAmerican Seed, 2005). Of the treatments with the best growth, all of the conventional slow release treatments and the organic low treatment stayed within 2 and 2.75 mmhos.cm-1, until after day 54 when the EC for the conventional high slow release treatment went over 3 mmhos.cm-1. The two slow release rates that failed to produce acceptable growth were the moderate and high levels of the organic fertilizer. These treatments were both above 2.5 mmhos.cm-1 by experiment day 23 and raised to an unacceptable 5.62 and 8.28 (moderate and high rates respectively) by experiment day 67. These high salt levels no doubt contributed to poor plant growth. Among these treatments, those plants that survived the toxic salt levels had poor root development and had very clorotic leaves (SPAD readings of 5.38 for the high organic slow release treatment.

Based on published recommended EC rates and growth data gathered in this experiment, a conventional slow release fertilizer like 20-7-10 Nutricote rates of 1.8 kg.1 m-3 to 3.6 kg.1 m-3 (low and moderate rates in this experiment) could be recommended. Because there is no significant difference in growth parameters between any of the rates of Nutricote, there is no benefit to using a rate higher than 3.6 kg.1 m-3. The slow-release organic fertilizer,10-2-6 Lawn Restore, at the low rate 3.6 kg.1 m-3, although not significantly different, showed slightly poorer growth than the conventional slow release treatments at all rates.

The low and moderate rates (75 and 150 ppm N respectively) of both conventional and organic soluble fertilizers had the best growth responses of soluble treatments. The conventional and organic low treatments (75 ppm N) stayed below 1.6 mmhos.cm-1 for the duration of the experiment. The moderate soluble treatments reached 2.5 mmhos.cm-1 at their highest, while the conventional soluble high treatment had a maximum of 4.4 mmhos.cm-1 and the high organic reached 3.96 mmhos.cm-1. These high salt levels make soluble constant liquid feed rates over 150 ppm N ill-advised. Data from this experiment suggests that rates of 75 to 100 ppm N from either conventional or organic constant liquid feed are appropriate for this crop.

Because lisianthus is a pH sensitive crop, with an approximate pH requirement of between 6.3 and 6.7, it is necessary to address the impact that N form may have on media pH (Harbaugh and Woltz, 1991). Conventional and organic fertilizers traditionally have different forms of N. The conventional slow release fertilizer had a concentration of 9.3:10.7 NH4-N to NO3-N while the organic slow release had a NH4-N:NO3-N ratio of 4:1. The conventional soluble fertilizer had a NH4-N to NO3-N ratio of 1:3 while the organic soluble feed was 4:1 NH4-N:NO3-N. The conventional organic fertilizers fell below optimal pH levels until experiment day 39, but the pH gradually increased, bringing the low and moderate conventional slow release treatments to 6.6 and 6.7 by the end of the experiment. The high conventional slow release treatment had consistently low pH values. Because the conventional fertilizers had a lower concentration of NH4-N than the organic fertilizers, it is reasonable to presume that the pH of the organic treatments would be lower than those of the conventional treatments. pH would be lowered when there is a greater amount of NH4-N being absorbed by plants. When more NH4-N is taken up by plants, the plant releases H+ ions which lowers pH. This is not the trend that was observed in this experiment, however. The NO3-N from the organic slow release fertilizer was available much faster than was anticipated. Because of the high amounts of NO3-N in the organic slow release fertilizer, the pH rose dramatically, reaching a pH of 7.7 in the organic high slow release treatment by experiment day 39 and then plummeting to 5.19 by the end of the experiment. The pH of the organic soluble feed treatments followed anticipated trends more closely. Because the NH4-N of the organic soluble feed was much more available to the plants for uptake, the pH of the media was lower than the organic slow release pH values.

Although the uptake of NH4-N can greatly lower the pH of media, it is important to recognize that the pH fluctuations may not be entirely due to N absorption by plants; microbial activity undoubtedly impacted the media pH, as well.

Final growth data that was collected corresponds with EC and pH data. The treatments that showed the greatest deviation from suggested EC and pH rates also had the poorest growth. By experiment day 39, the conventional slow release treatments had significantly better growth than both the moderate and high rates of organic slow release fertilizer, a trend that continues throughout the duration of the experiment. These two treatments also had the highest EC and the highest pH before this day. From experiment day 39 continuing to the end of the experiment, the organic moderate and high slow release treatments performed worse than the no fertilizer control. In the soluble treatments, the conventional moderate treatment was quickly established as having highest growth stages. At experiment day 39, the conventional and organic high rates of soluble feed were at significantly lower stages than the conventional moderate treatment. This continued throughout the experiment with the high soluble treatments eventually being at significantly lower stages than all other soluble treatments except for the control. Although not significantly different at α=0.05, the no fertilizer control had higher mean stage rating than both soluble high treatments beginning at experiment day 39.

Based on this experiment, it is possible to use either conventional or organic fertilization methods in the production of cut-flower lisianthus. The conventional slow release fertilizer used (Nutricote 20-7-10) was effective at all tested rates, so the low and moderate fertilization rates (1.8 kg.1 m-3 to 3.6 kg.1 m-3) tested here are recommended. The organic slow release fertilizer that was used proved to be an inappropriate choice for this crop at rates over 3.6 kg.1 m-3 because of the high rate of NO3-N that was released and negatively affected EC and pH early in the cropping cycle. The Lawn Restore organic slow release fertilizer has the potential to be an adequate choice for fertilizer in field settings due to the cool soil temperatures that would slow the release of NO3-N; this should be studied further. Lisianthus has moderate fertility requirements, therefore a constant liquid feed of 75 to 150 ppm N from either a conventional or organic source will provide adequate nutrition. This research offers recommendations to lisianthus producers who are looking for feeding options beyond the suggested 1200 ppm N once per week (Frett et. al., 1988). The options of constant liquid feed or a slow release fertilizer are very compatible with the automated production used by many of today’s market farmers.

Germination and Seedling Development of Giant Oriental Poppy

Petri plate seed germination. Germination is defined as “the emergence and development from the seed embryo of those essential structures which. . .are indicative of the ability to produce a normal plant under favorable conditions”. Radicle emergence in the Petri plate study occurred under such favorable conditions as defined by AOSA in Rules for Testing Seeds and therefore the results from this preliminary test suggest the maximum germination expected from each cultivar and seed lot in growth chamber experiments. In the growth chamber experiments, “favorable conditions” are not necessarily provided based on treatment regimes and because seed are sown in a commercial root medium that may have affected the ability of the seedling to penetrate. The average germination for the single lot of ‘Temptress White’ was 44%. ‘Temptress Orange’ average germination percentage was 60% for lot one and 82% for lot two.

Light or dark germination study (Experiment 1).

Germination of the white cultivar was 38% less than that of the orange cultivar which had 81% germination after 13 days (p<0.0001). Interestingly, the germination of the white cultivar was similar to the results of the Petri plate study while the germination of the orange cultivar was about 20% less in the Petri plate study. White poppies germinated about 0.8 d later than orange poppies (p=0.0129). Differences in percent germination between cultivars began five days after sowing (DAS) in the 16 h light treatment (p=0.0009) and in the 24 h dark treatment (p=0.0052) and were apparent throughout the rest of the experiment.
Germinating seeds under 16 h of light compared to 24 h of darkness resulted in about 8% more germination, but this difference is only significant at α=0.1 (p=0.0931). This suggests that the current recommendations for leaving Papaver orientale seed exposed to light during germination (Dole and Wilkins, 1999; Fred C. Gloeckner, 2005; Nau, 1993, Ohio Florists Assoc., 1999; Perry, 1998) is not essential; in fact, germination of the white cultivar was similar under both light and dark conditions.

Literature reviews in research reports of other ornamental plants have also suggested that recommendations for environmental conditions during germination are variable across published sources (e.g. Shoemaker and Carlson, 1992). An experiment testing the germination conditions for fibrous-rooted begonia determined that light was required for germination, but at a shorter period than was reported in published works (Shoemaker and Carlson, 1992). The effect of light on another member of the Papaver genus, Papaver dubium (long-headed poppy), indicated that germination was “unaffected or slightly inhibited by light” (Wesson and Wareing, 1969). Chen (1968) found that the light by temperature interaction had a great impact on overcoming light-inhibited dormancy of Nemophila insignis; this interaction should also be investigated with the ‘Temptress’ cultivar. The fact that poppies do not require light for the first few days after imbibition can be of benefit to growers in that a variety of light environments will result in optimal germination, from dark germination chambers to ambient light conditions on a greenhouse bench. Because light is not a critical consideration during the first stage of germination, growers can inexpensively and easily maintain a high humidity environment by covering the germinating seeds with either a plastic bag or tray (Stamback, pers. communication).

Air temperature germination study (Experiment 2).

Germination percentage of the white cultivar was about 38% less than that for the orange cultivar (p<0.0001) which was consistent with results from Experiment 1. The germination of the white cultivar was similar in the air temperature experiment as it was in the Petri plate study, but was again about 20% greater in the air temperature experiment for the orange cultivar. Beginning at three days after sowing, germination was different between the white and orange cultivars at 24oC (p=0.0159) with the germination percentage of the white cultivar at 9% and the germination percentage of the orange cultivar at 18%. The results of this experiment refute the idea that heat accumulation plays a role in germination of Oriental poppies because seeds at 18oC germinate just as quickly as seeds at 24oC and 32oC. Cultivar differences were the only significant factor in this study until eleven days after sowing when germination was different between 24oC and 32oC air temperature for ‘Temptress Orange’ (p=0.0413). At day eleven, mean germination of ‘Temptress Orange’ at 24oC was 87% while germination of the same cultivar at 32oC was only 78%. While air temperatures as high as 32oC (90oF) did have a marginally negative affect on poppy germination (p=0.0947), temperatures between 18oC and 24oC (65oF and 75oF) resulted in maximum germination percentages. This result is consistent with most of the literature (Dole and Wilkins, 1999; Nau, 1993, Ohio Florists Assoc., 1999). However, in a preliminary study conducted in the Kansas State University greenhouses, germination of ‘Temptress Mix’ poppy seeds occurred after air temperatures had reached 43oC (110oF; data not shown). Seedling development (Experiment 3). The germination percentages that were achieved in the seedling development study mirrored the light and dark experiment, and the air temperature experiment as well as the Petri plate study. The white cultivar germinated at a rate of 50% and the orange cultivar at a rate of 77%. Because the differences between cultivars were so great that they masked the treatment affects of the environmental parameters, additional statistics were completed ‘by cultivar’. At final harvest, the percent of live seedlings was calculated. The average stage was also assessed at this time. Though there were no significant differences in the average stage at final harvest between the air temperature treatments, there were significant differences in the percent of plugs alive at final harvest between air temperatures. Low and moderate air temperatures proved to support a higher percent of seedlings alive at day 21 in both cultivars. The percent alive at final harvest had similar values to the germination percentages that were found in all experiments and the Petri plate study. Surprisingly, the average stage at final harvest showed no statistically significant differences between any of the temperature treatments, however considerable visible differences can be noted between low air temperature and high air temperature treatments. Upon completing the 21 d cycle in their respective chambers, plugs from 16oC and 33oC treatments were placed in moderate temperatures (24oC) for seven to ten days. The plugs were moved to equilibrate the development environment to assess if the negative high air temperature effects could be reversed. This observation showed that the plugs that had been moved from a low air temperature to a moderate air temperature looked to be much larger and healthier than those that were moved from high air temperatures to moderate air temperatures leading to the conclusion that damage from heat stress within the first weeks of development is not easily overcome. Because this observation was only based on one replication from the low air temperature treatment and two replications from the high air temperature treatment, no statistics are shown. The many different treatments in this experiment allowed interactions between air temperature, humidity and fertility to be assessed. Within the low air temperature treatment, the high humidity environment allowed for significantly more seedlings of the white cultivar to be alive at final harvest than in the ambient treatment (p=0.0167) while the humidity and air temperature interactions had no significant affect on the percent of seedlings alive at harvest in moderate or high air temperatures in the white cultivar or in any air temperatures in the orange cultivar. The stage of seedlings at final harvest was significantly higher in the high humidity treatment over the ambient treatment in both the moderate and the high air temperature treatments for cultivars. This leads to the conclusion that lower air temperatures (16oC to 24oC) and/or humid environments would encourage successful seedling development. Cooler air temperatures and smaller VPD allow for less water loss due to transpiration, therefore keeping seedlings turgid in this delicate stage. Fertilization began ten days after sowing seed, therefore one would expect that the fertilization treatment would only affect the percent of seedlings alive at final harvest and the stage of the seedlings at final harvest. The low air temperature treatments showed differences between fertilized plugs and non-fertilized plugs in percent alive at harvest in both cultivars (‘Temptress White’ p=0.0196, ‘Temptress Orange’ p=0.0304) and in stage at harvest in the orange cultivar (p=0.0018). Oddly enough, the fertilizer had a negative affect on the white seedlings at low air temperatures, while the orange cultivar responded favorably to fertilizer in regards to both percent alive at harvest and stage at harvest. At high air temperatures, only the orange cultivar showed a significant reaction to fertilizer, with stage at harvest being increased in seedlings that were fertilized. ‘Temptress White’ and ‘Temptress Orange’ seedlings that were fertilized showed a significantly higher number of seedlings alive at harvest at low and moderate air temperatures than at high air temperatures. In the white unfertilized seedlings, the percentage of seedlings alive at harvest was greater in the moderate temperature than in both the low or high air temperatures. The moderate air temperature allowed for greater stages at final harvest over the high air temperature in both cultivars and over the low temperature in the orange cultivar. The germination differences that were consistently observed between ‘Temptress White’ and ‘Temptress Orange’ poppies could be due to a lack of or less carotenoid synthesis in the white mutant cultivar; however, all photosynthetically-active life must contain carotenoids (Park et al., 2002). Carotenoids are present in large amounts in orange (wild-type) Eschscholzia californica (California poppy) where the orange trait is dominant over the mutant white traits. When white petals of California poppy occur, they are found simultaneously with white pollen and in most species, flowers with white pollen are sterile (Wakelin et al, 2003). Unusually, the white pollen of California poppies is fertile, but contains no carotenoids, although the authors state that California poppies do not require carotenoids for pollen fertility (Wakelin et al., 2003). These findings could be related to the consistently poorer germination of the white cultivar in our research. Based on these experiments, germination conditions that can be recommended to growers for Papaver orientale ‘Temptress’ are light or dark conditions at multiple air temperatures ranging from 16oC to 24oC. Maximum germination consistently occurs within 10 days after sowing. Cultivar differences are substantial as ‘Temptress Orange’ resulted in nearly twice germination of ‘Temptress White’ and germinate about one day faster than the white cultivar (Tables 1 and 4). These findings are of value to cut flower producers in that they suggest ease of germination for this species across a range of environmental conditions such that special equipment or care does not seem to be necessary to achieve maximum germination, which is predominantly influenced by genetic potential and/or seed quality. Considering the results of the seedling development study, it is suggested that poppies be allowed to germinate and develop in lower temperatures. Development was visibly reduced in seedlings from the high temperature treatments.