Although crop growth and yields mostly depend on the combination and concentration of mineral nutrients available in the soil, the ability of carrots and green onions to uptake N, P and K eventually determines their growth and development. Plants with poor nutrient uptakes will lead to nutrient deficiency, resulting in reduced crop yield or reduced yield quality.

Carrot growth and yields: The use of liquid organic fertilizer significantly affected plant height, shoot dry weight, tuber fresh weight and tuber diameter of carrots (p<0.05 at 0.0004, 0.0010 and 0.0005, respectively) but not the number of leaves and tuber lengths (p<0.05 at 0.0530, 0.0010 and 0.1600). The effects of liquid organic fertilizer concentration on the growth and yields of carrots were presented in Fig. 3.

It appeared that the use of 50% of liquid organic fertilizer has been sufficient enough to increase carrot growth (plant height and shoot dry weight) and yields (tuber fresh weight and tuber diameter) since higher concentration produced lower growth and yields (Fig. 3a, c-e). These increases could have been due to increased N, P and K uptakes by carrots (Fig. 1a-c), which later accelerated photosynthesis and tuber development. For example, for tuber fresh weight, it is found that the correlation coefficient between tuber fresh weight with N, P and K uptakes were 0.694, 0.869 and 0.862, respectively. These strong relationships indicated that an increase in tuber fresh weight was determined by N, P and K uptakes by carrots. Overall effects of liquid organic fertilizer on carrot growth and yields from this study were in line with that found by other researchers40, in which dry matter, tuber weight and carotenoid contents of carrot fertilized with liquid organic fertilizer were higher than those of fertilized with synthetic fertilizer. Another research41 also concluded that the application of liquid organic fertilizer increase petiole length, shoot fresh weight and tuber diameter of carrot. In addition, residual effects of yearly vermicompost application to this production site might have played effects to establish a better growing environment as well as tuber development for carrots. Indeed, vermicompost amendment into the soil improved soil pH, aggregates, bulk density, water-holding capacity, organic matter, micro and macro-nutrients and soil biological properties34.

Image for - Liquid Organic Fertilizer Increased Nutrient Uptakes, Growth and Yields of Organically Grown Carrot and Green Onion
Fig. 3(a-f): Effects of liquid organic fertilizer (LOF) on (a) Plant height, (b) Leaf number, (c) Shoot dry weight, (d) Tuber weight, (e) Tuber diameter and (f) Tuber length of carrots
Means of treatment followed by the same letter in each figure are not significantly different according to least significant difference p<0.05


Image for - Liquid Organic Fertilizer Increased Nutrient Uptakes, Growth and Yields of Organically Grown Carrot and Green Onion
Fig. 4(a-f): Effects of liquid organic fertilizer (LOF) on different parts of green onion, (a) Leaf number, (b) Tiller number, (c) Shoot fresh weight, (d) Root fresh weight, (e) Shoot dry weight and (f) Root dry weight of green onion
Means of treatment followed by the same letter in each figure are not significantly the different according to least significant difference p<0.05

Green onion growth and yields: The use of liquid organic fertilizer significantly affected shoot fresh weight, root fresh weight, tiller number, shoot dry weight and root dry weight of green onions (p<0.05 at 0.0200, 0.0002, 0.016 and 0.0100, respectively) but not the number of leaves (p<0.05 at 0.0800). The effects of liquid organic fertilizer concentration on the growth and yields of green onion are presented in Fig. 4.

Positive effects of liquid organic fertilizer to increase shoot fresh weight, root fresh weight, tiller number, shoot dry weight and root dry weight of green onions (Fig. 4b-f) but not leaf number (Fig. 4a), could have also been related to increased N, P and K uptakes by green onions (Fig. 2a-c). Similar to the case of carrot responses, increased nutrient uptakes by green onions accelerated plant metabolisms and hence increased the growth and yields of green onions. This study revealed that to shoot the fresh weight of green onions, the correlation coefficient between tuber fresh weight with N, P and K uptakes were 0.699, 0.454 and 0.682, respectively. These relationships indicated that increased shoot fresh weight was determined by N, P, K uptakes by green onions. It appeared that the use of 100% liquid organic fertilizer generally increased the growth and yields of green onion. Considering the economic value of green onion relies on its shoot fresh weight, the application of liquid organic fertilizer was sufficient at 25 ppm (Fig. 4c). This result was in line with that concluded by other researchers26, where green onion fertilized with cow manure liquid organic fertilizer at a 50% concentration had higher fresh weight than those fertilized with 0, 25 and 75% concentration cow manure liquid organic fertilizer. This research also revealed that the use of 25% guava waste liquid organic fertilizer produced a fresh weight of green onion significantly higher than those of fertilized with 0, 50 and 75% concentration guava waste liquid organic fertilizer. ‘A similar conclusion was reported25 that green onion fertilized with 2 mL L–1 of liquid fertilizer generally had higher growth and yields than those of 0 and 3 mL L–1. In addition, the use of liquid organic fertilizer has been also reported to increase plant height, leaf number, tiller number and bulb yields of shallot42.

This research suggested that the use of liquid organic fertilizer in organic vegetable production systems becomes inevitable to improve the effectiveness of solid organic fertilizer application in organic farming. As nutrient supplementation, it is demonstrated that the use of liquid organic fertilizer increased N, P and K uptakes as well as the

growth and yield of carrot and green onion, respectively. However, it did not increase the leaf numbers of both carrot (Fig. 3b) and green onion (Fig. 4a). It was also found that the use of 50 and 25% liquid organic fertilizer was able to increase the growth and yield of carrot and green onion, respectively. These results might be not separated from the fact that this experiment was conducted on an organic farm which takes at least three consecutive years of organic farming practices to have established organic growing conditions. Although crop responses to foliar fertilizer are different among species, plant ages and environmental conditions, further research should be addressed on the use of liquid organic fertilizer at lower concentrations and on evaluating the nutrient use efficiency of carrot and green onion in organic production.