High-quality plants are the ultimate goal of any grower. Compact growth and strong branching are among the features of a high-quality plant. As a result, these plants are tougher and more resistant to transport and other environmental stresses. Fertilizer also has an affect on plant size and stretching, and growth regulators are commonly utilized to achieve this goal.
Fertilizer application rate, nitrogen types, and phosphorus all play a role in a plant’s ability to stretch.
Fertilizer Application Rates
Adding additional fertilizer to a crop increases its growth rate. Too little or too much fertilizer can have a negative effect on plant growth, and excessive fertilizer can cause root damage or even death in the case of high levels of fertilizer salts in the soil. Fertilizer application rates should be kept in the middle of this range in order to control plant growth.
When fertilizer treatment rates are altered even little, plants like tomatoes respond dramatically. Low fertilizer application rates (50 ppm N) will not only limit the growth of a tomato plant, but will also limit the size of its leaves. Deficiencies in nutrients can be a problem, but in general crop quality is satisfactory. Tomatoes can be manipulated in height and size by withholding fertilizer from them up to a certain point.
There’s a noticeable difference between the tomatoes on the right and the left. It’s possible to reduce the fertilizer application rate if the crop quality is satisfactory.
Petunias that are fed at lower rates (less than 150 ppm N) similarly have a drop in growth and leaf size, but they are quickly deficient in nutrients, demonstrate poor quality, and are ill-equipped to deal with environmental stress. Micronutrients like iron and manganese, which are critical to plant health when applied at lower rates, are similarly affected by lowered fertilizer application rates. Although fertilizer rates can be adjusted to manage stretching and plant size, unlike tomato, crop quality is unsatisfactory.
The New Guinea impatiens have much larger plants. In the top picture, plants are stunted and chlorotic as a result of insufficient fertilizer application, whereas in the bottom picture, plants are healthier and larger as a result of adequate fertilizer use. However, the quality of the crops was degraded by reducing the amount of fertilizer used. It is possible to compromise plant quality by reducing fertilizer application rates. The end user’s quality and performance could suffer as a result of the new technology. When it comes to limiting plant height and development, withholding fertilizer is not always the greatest solution.
Nitrogen fertilization has long been viewed as a factor in plant growth and quality. It has long been considered that ammoniacal nitrogen causes plants to expand and grow larger, while nitrate nitrogen generates compact, firm growth and smaller leaves. This appears to be the case in practice. 20-10-20, which contains 40% ammonium and 60% nitrate, might increase stretching, greater leaf size, and softer overall growth than 13-2-13, which has only 6% ammonium and 94% nitrate. It’s important to note that if both fertilizers are used at the same nitrogen rate, 20-10-20 will deliver three times as much phosphorus as 13-2-13.
Due to the use of ammonium phosphate in their composition, nitrogen fertilizers with a high ammoniacal nitrogen ratio also tend to have greater phosphorus concentrations. Because calcium nitrate can precipitate with phosphate, fertilizers with higher nitrate ratios typically have little or no phosphorus content. Is the source of nitrogen responsible for the stretching of plants?
To test the effects of varied fertilizer ratios on bedding plants, Dr. Paul V. Nelson of North Carolina State University and his team experimented with ammoniacal to nitrate nitrogen fertilizer, while leaving all other nutrients the same. In terms of plant growth, there was minimal difference. A new study disproves the long-held belief that ammonium causes plant stretching whereas nitrate leads in shorter, leaner plants. Dr. Nelson concluded that plant height and growth are not affected by the type of nitrogen.
After that, he turned his attention to phosphorous. Phosphorus levels varied in his studies, but nitrogen and all other nutrients were maintained at their original amounts. Bedding plants that received a high phosphorus fertilizer were taller than those that received a low phosphorus fertilizer, according to the results. The finding was self-evident: the amount of phosphorus in a fertilizer has a greater impact on plant growth and stretching than the nitrogen form.
In this picture, you can observe the effects of phosphorus deficiency, which include stunted growth and darkening of the leaves. However, sustained phosphorus deprivation can lead to foliar necrosis and a decrease in crop quality, which are both good quality qualities for most plants. In order for a water-soluble fertilizer to be effective, it must contain at least 10% phosphorus (P2O5) by weight (i.e. fertilizers with analyses such as 20-2-20 or 20-3-20). In some cases, plug crops prefer greater phosphorus levels and may benefit from 20-5-20 analyses. Other than causing plants to grow taller, fertilizers like 20-10-20 and 20-20-20 supply more phosphorus than crops require.
Look at how phosphorus affects tomato development. The plant on the left has normal phosphorus levels, whereas the one on the right has low phosphorus levels and is shorter and smaller as a result. This information comes from apps.cdfa.ca.gov/frepdocs/Tomato.html, Jim Richards, UC Davis.
Can Over-Fertilizing Kill Plants?
Using too much fertilizer can permanently harm or even kill your plants, as we’ve already established. Fertilizer burn is another possibility.
What is Fertilizer Burn?
Over-fertilization causes scorched foliage as a result of fertilizer burn. Gardeners who overfertilize plants or apply fertilizer to moist leaves are to blame for this problem. The sodium in fertilizers might cause your plants to become dehydrated. As a result of over fertilization, the leaves turn yellow or brown.
In most cases, the first signs of fertilizer burn occur within a few days. Symptoms may not appear for several weeks using slow-release fertilizers. It is possible to see fading, wilting, browning, and yellowing of the leaves. You’ll notice white, brown, and yellow streaks in your grass and garden after applying fertilizer.
How to Prevent Fertilizer Burns
Fortunately, you can easily prevent fertilizer burns. Here are some of the tips you need to keep in mind:
Water your plants thoroughly after applying granular fertilizer to remove any remaining residue and to allow the salts to penetrate the soil deeply.
Slowly releasing the nutrients into the soil rather than releasing them all at once, compost decreases the chance of fertilizer burn. At the very least, you should add one to two inches of compost per year.
In times of drought, plants are more susceptible to fertilizer burn because the fertilizer is concentrated. Wait until moisture levels have improved before applying fertilizer during warmer seasons.
The Benefits of Mini Greenhouse Gardening
You may minimize fertilizer burn by purchasing a tiny greenhouse. You may not need to fertilize your plants if you can regulate the temperature, humidity, and other key aspects in your greenhouse’s climate. Here are a few other advantages to owning a greenhouse:
Keep your plants safe from harmful insects that’ll eat your produce
Aphids, cabbage worms, flea beetles, and other insects love to eat your leaves and produce. It’s possible for your plants to become more vulnerable to various diseases when this happens. It may also have an impact on the growth and harvest of crops. A greenhouse reduces the risk of inviting unwanted pests.
Great for gardeners who want to know more about greenhouse gardening
Several insects like to feed on the leaves and products of your garden. As a result of this, your plants are more vulnerable to several illnesses. Plant development and harvest could also be affected by the weather conditions. Because they’re in a greenhouse, they’re less likely to be eaten by these pests.
Start plant growth early
Use a tiny greenhouse before the cold season begins in your location to start planting. Plants can be moved from the greenhouse to the garden once the weather warms up. In order to get the benefits of planting early, you’ll need to do so sooner than you originally planned.
Protect your plants from erratic weather
During the chilly winter months, most plants, especially the more delicate varieties, are unable to thrive. You can keep your plants safe from the elements with a small greenhouse. Inside the enclosure, they’ll be secure and sound until spring comes back around.
The slow growth of loquat rootstocks is a major impediment to the widespread use of grafting as a way of cultivating new varieties. Seven different fertilizer formulations, five water-soluble fertilizer formulas, organic fertilizer, and controlled-release fertilizer were tested on the growth of loquat rootstock seedlings in this study. There was also a CK (control without fertilization) test. Plant height, stem thickening and lignification, leaf area, root development, dry matter accumulation, spatial distribution of nutritional components, and stem cross-sectional anatomy were among the growth indicators that were assessed. Adding microelements to fertilizer delayed the lignification process of the cambium, which exhibited the largest improvement in stem thickness, according to the results of the study. Fertilizers rich in phosphorus can help plants develop fibrous roots, but excessive phosphorus delivery can disrupt nitrogen absorption and use in root systems and lead to increased lignification and a decrease in aboveground growth. In order to promote quick growth and speed up the lignification process in loquat rootstock seedlings, this study’s findings may give theoretical support for the development of an optimal fertilization formula and procedure.
As a subtropical fruit native to China, the loquat (Eriobotrya japonica (Thunb) Lindl., Maloideae, Rosaceae) constitutes one of the most important fruit species in China1 Asexual propagation of loquat varieties has been hindered by several issues, including the fact that seed reproduction takes a long time and the seedling progeny cannot maintain the variety’s characteristics due to genetic variation2. Another problem is that explants are prone to browning in the asexual propagation system because of the higher phenol content in loquat compared to other Rosaceae fruit trees; therefore, callus proliferation requires strict selecion.2 Zhang3 reported that in tissue culture of loquat, the most susceptible leaf explants were those collected 5 days after the bud sprouting, while those collected 10 days later showed minor browning symptoms and rapidly induced large quantities of granular light-green tight, high quality calluses, while those collected 15 days later showed yellow and loose calluses, with lower proliferation efficacy than those collected 10 days earlier. In addition, there are a variety of ploidy materials and varieties of loquat that have different requirements on the medium formulation, especially hormone concentration and composition4, so the asexual propagation system suitable for one loquat variety cannot be directly copied and extended to other varieties, and most importantly, even if asexual plant regeneration is successful, it will take another 7–8 years to grow into adult fruit trees. As a result, grafting is a key tool for cultivating new cultivars today. Rootstocks must grow for around 2–3 years before they can be used for grafting, which severely limits the breeding efficiency of loquat. In the field, fruit setting can begin in the third year after grafting. Fast-growing approaches for loquat rootstocks have not received the attention they deserve.
Main stem diameter is a significant factor in measuring rootstock growth and quality5,6. The stem diameter of rootstocks was found to have a substantial positive correlation with plant height, crown width, branch number, leaf number per plant, and Idesia’s leaf area index. Yet another view was that rootstocks with excessive thickness could impair the healing of graft unions and lower the success rate of grafting 8. Furthermore, a third theory proposed that rootstock age may influence grafting survival rates and scion growth.9 Rootstock quality can be affected by both the diameter of the stem and the degree of lignification, according to all of these arguments.
Rootstock’s initial development and quality can be improved through fertilization. Superphosphate enhanced plant height and stem diameter the most after 30 days of transplanting, according to Silva12. Plant height and leaf area increased with the addition of nitrogen (N), but the stem diameter and root dry mass data revealed a linear decrease. It has been found that organic fertilizer can raise the TN and AP content in plowing layer soil and promote the root development of grapes, according to Tomislav14 Soil health and plant growth can be improved by using the correct form, content, and quantity of nutrients, according to the results of this study. Research on the impact of different fertilizer formulae on the initial growth of rootstock seedlings is scarce, and publications on the connections between fertilizer applications and the stem lignification process and root morphogenesis are also infrequent. The goal of this research is to identify the best fertilization formula for loquat rootstocks that can maintain the most vigorous development as well as the most appropriate lignification procedure.
Effects of different fertilizer formulas on the height of loquat seedlings
Table supplement 1 shows that increasing the amount of nitrogen in fertilizer or adding trace elements can help enhance shoot growth in loquat rootstock as illustrated in Figure 1. HN-treated loquat rootstocks reached 60.33 cm in height at the end of the experiment, while MF-treated loquat rootstocks reached 64.86 cm in height and 11.6 times greater than their baseline values. From January to March, the plant height of the HN-treated seedlings showed the highest increase (57.9%) during this period, and the second was shown by the MF-treated seedlings (42.5%). In the HP therapy, the lowest percentage of CK was 29.6 percent, and the increase was just 5.6 percent.
Effects of different fertilizer formulas on loquat leaf growth and development
Fig. 1 and Table supplement 1 show that increasing the amount of N in fertilizer or adding trace elements can increase the growth of loquat rootstock. HN-treated loquat rootstocks reached 60.33 cm in height at the end of the experiment, while MF-treated loquat rootstocks reached 64.86 cm. A 57% increase in plant height was seen in the HN-treated seedlings from January to March; the MF-treated seedlings came in second (42.5 percent ). The HP therapy resulted in a decrease of 29.6 percent, whereas the CK increase was just 5.6 percent.
Effects of different fertilizer formulas on root morphological development
Figure 3 and Table 2 indicate that HN treatment resulted in the highest overall root development, while HK treatment resulted in the lowest. However, the average root diameter of HP-treated seedlings was the smallest, which may indicate that N and P promote root development in different ways, N increases root growth quantity and makes root thicker; P promotes a large number of fibrous roots, increase the surface area of roots, and improve the absorption capacity of roots to water and nutrients; too much K will weaken root development.
Comparison of dry matter accumulation of rootstock seedlings under different treatments
Table 3 shows that varied fertilization formulations can alter biomass accumulation. HN seedlings had the highest fresh weight of leaves and roots, OF seedlings had the highest dry matter accumulation in leaves, HP seedlings had the highest dry matter accumulation in roots. MF seedlings had the highest stem fresh weight.
Effects of different fertilizer formulas on the spatial distribution of nutrients in seedlings
The concentrations of nitrogen, phosphorus, and potassium in dried loquat root, stem, and leaf samples were also analyzed. The CF treatment resulted in the greatest accumulation of N and P in the roots, stems, and leaves of loquat rootstock seedlings, while the HK treatment resulted in the greatest accumulation of K in these same tissues (Table 4), suggesting that plants have N and P uptake and utilization mechanisms that work in concert, but that K uptake and utilization mechanisms are separate (Table 4). Unexpectedly, the HN treatment had the lowest N buildup in the roots, stems, and leaves of plants, which may be connected to the ease with which water-soluble N is lost during leaching.
Effects of different fertilizer formulas on lignification of stems and roots
Saffron staining was visible in the cambium and periderm under the HN treatment (Fig. 4HN) and in the cambium and secondary xylem under the HP treatment (Fig. 4HP). The stem tissue under the MF B and HK treatments showed relatively slight lignification in the cambium and periderm compared to that under the other fertilizer treatments, while the lignification in the CK was the most severe, as whole cambi
Furthermore, the stem pith cells (red punctuate staining) under the B, MF, and CF treatments were observed to have deeper saffron staining than under the other fertilizer treatments. There was reduced lignification of the pith cells in the HN, HP, and HK treatments compared to the control. As a result, it was hypothesized that increased proportions of N, P, or K in fertilizer could slow down the lignification process of stem pith cells compared to NPK balanced fertilizer.
Paraffin sections (Fig. 6) further revealed that the HP treatment resulted in the lowest degree of root lignification while the B treatment was most severe, notably in the cambium. In the pith tissue, therapy for OF and CF triggered lignification.
Effects of fertilizer formulas on lignin accumulation in the stems and roots
HP-treated loquat seedlings had the largest lignin accumulation in the stems, while B-treated loquat seedlings had the most root lignin accumulation, and the HK-treated loquat seedlings had the lowest stem accumulation. Lignification weakens the rootstock’s ability to absorb and transport nutrients but has little effect on elements with high mobility, such as N and K, while P accumulates.
Root and stem lignin concentrations vary depending on the treatment.
Means and standard deviations (SDs) are included in the data set. In the various plant portions and fertilizer treatments, the bars (i.e., the means) with various letters are substantially different (P 0.05).
Correlation analyses of growth-related indicators of loquat rootstock seedlings
There was a significant relationship between plant height (contribution rate of 65.076 percent), main stem diameter (contribution rate of 19.143 percent), and leaf SPAD values (contribution rate of 8.577 percent) and the differences in growth and development of loquat rootstock seedlings under the different fertilizer treatments (Table 5) Table 6 also showed a substantial correlation between the accumulation of N and P in the roots and leaves, as well as K in the roots and stems. Loquat may have two distinct mechanisms for absorbing N and P and K, as N and P preferentially collect in the leaves and K preferentially accumulates in the stems.
Exogenous nutrients have an essential role in determining the quality of rootstocks, even though many studies have demonstrated that plant development and nutrient use, as well as root architecture, are mostly controlled by genotype15–17. According to He18, increasing soil K levels resulted in an increase in N, K, Cu, and Zn uptake by cocoa plants and a decrease in the concentrations of other nutrients such as P, Ca, and Mg. Adding N to Arabidopsis thaliana resulted in large increases in stem diameter, cortical thickness, flower ring radius, midrib thickness, leaf and stem vascular size, whereas adding phosphorus resulted in considerable increases in stem xylem thickness (19). Loquat tree root development is regulated by fruit load and mediated by competition for carbohydrates, according to Reig20. According to these studies, different plants have distinct optimal ranges of nutrient demands that can be met by various nutrient concentrations, ratios, and even availability.
We know for a long time that the importance of N in encouraging fast plant growth is well-known, but most previous study has focused on the grafted seedling, or in other words the interaction between rootstocks and scions. Shoot height and stem diameter of rootstocks treated with HN were somewhat lower than those treated with MF in this study (Figs. 1–2). A lack of vegetative development in the presence of high N suggests that the plant’s ability to utilize the nutrients it receives may be compromised13,21. In contrast, the HN treatment resulted in lower SPAD values and NPK concentrations than the CF treatment (Tables 1–4). The dilution effect on NPK accumulation in leaves has been shown in previous research on pear22 and grape25, which revealed the opposite results: increasing N can expand leaf area consistently and significantly, but it leads to relatively lower NPK accumulation in leaves.
Root development was discovered to be strongly influenced by the N form of P in this study, despite the fact that P is widely regarded to have a considerable effect on root formation. HN had the highest urea-N content while HP had just ammonium-N. Rootstocks under HP treatment exhibited the longest root length, the largest root surface area, the greatest root dry mass and root volume, the largest amount of fibrous roots but the lowest root fresh weight (Table 7). When compared to other treatments, HN treatment resulted in fully formed roots as well as the maximum root fresh weight (Table 3). According to these findings, P and ammonium-N together can greatly stimulate the development of fibrous roots, but too much ammonium-N may damage the root system and impede the growth of loquat rootstock shoots. Peach24 reported that ammonium-N absorption increases dry matter accumulation of roots, but too much ammonium-N is detrimental to the thickening of the stem, which is consistent with our results, while grape25 found that both ammonium-N and nitrate-N showed less promoting effects on increasing root/shoot ratio than that of amino acid-N, which is consistent with our results. According to these findings, various plants may have distinct preferences for nutrient uptake and different methods of converting and utilizing mineral nutrients than previously thought.
Table 2 shows that trace element fertilizers had a greater impact on stem thickening than the HN treatment. It showed in Fig. 4 that the lignification degree of the stem cambium was the highest under the HN treatment, but the lowest under the MF treatment, it could be inferred that excessive N accelerates the stem cambium lignification process, while microelement fertilizer can effectively delay it, thereby increasing the meristematic ability of cambial cells and promoting the thickening of stem.
Material and Methods
Tested seedling preparation
In 2017, we began collecting loquat seeds from fully developed fruits at the end of May. A plug plate was used to grow thousands of the artificially germinated seeds for 10–15 days, then the seedlings with the most potential were selected and transplanted into 1.5 L flowerpots (upper diameter of 16 cm, bottom diameter of 11 cm, height of 14 cm, one seedling in each pot) in which peat (pH = 6.5) served as the medium. There were three replicates of the experiment, each with 30 randomly selected seedlings.
Treatments and experimental design
The entire experiment took place in a greenhouse at the Shanghai Academy of Agricultural Sciences in Shanghai, China’s Feng Xian neighborhood. This experiment used commercial fertilizers to mimic conventional field fertilization as closely as possible, so we analyzed the nutrient element content and proportion of each fertilization formula to arrive at eight fertilizer treatments (Table 7), including five water-soluble fertilizer formulas (HN (high-nitrogen fertilizer), HP (high-phosphorus fertilizer), HK (high-potassium fertilizer), and B (balanced ferti- (CF). There was also a control (CK) that wasn’t fertilized.
Every week from August to October, the loquat seedlings were treated with 1 g of water-soluble fertilizer (HN) and every two weeks from November to April with 2 g of water-soluble fertilizer (HN, HP), and from May to August, the dosage was increased to 5 g of water-soluble fertilizer per pot. In the OF and CF treatments, 25 g of each was immediately mixed into the cultivation substrate once every three months, whereas the CK treatment got simply water.
During the course of the experiment, researchers measured the plants’ height, main stem diameter, leaf number, and leaf SPAD values on a monthly basis. They also analyzed the leaf area, dry and fresh weight of the above- and below-ground parts, root morphological characteristics, lignin content of roots and stems, and distribution of nutrients. Furthermore, paraffin slices were used to examine the loquat stems’ anatomy.
Measurements were made using a ruler, Vernier caliper, chlorophyll meter, and portable area meter to determine plant height, length, and diameter of the loquat seedlings’ leaf blades. The SPAD values of the leaves were determined using a chlorophyll meter, and the leaf area was determined using a portable area-meter (Li-3000C, LI-COR, USA).
By scanning, imaging, and analyzing the root morphology of the seedlings with the GXY-A root analyzer.
The Kjeldahl method was used to assess the total nitrogen (TN) content, the colorimetric method with ammonium molybdate was used to determine the total phosphorus (TP), and flame photometry was used to determine the total potassium (TK) content28. The Hu29 technique was used to measure the lignin content.
For each treatment, there were three independent replicates in a totally randomized design. Prism 4 (GraphPad, Lo Jolla, CA) was used for statistical analysis (Student’s t-test and ANOVAs) and charting, while SPSS 18.0 was used for principal component analysis (PCA) and correlation studies (SPSS Inc., Chicago, IL). P 0.05 was considered statistically significant for any differences in results.
We may conclude that manipulating fertilizer can affect the height of plants and the growth of crops. When it comes to crop growth, the long-held belief that ammonium extends plants while nitrate promotes compactness is not as crucial as previously thought. It is possible to improve crop quality and consumer happiness by reducing fertilizer application rates, although this is not always the case. Reduced phosphorus application rates are the only way to reduce plant stretching without affecting crop quality.