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  • Author or Editor: Jongtae Lee x
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A field experiment was conducted to evaluate yield performance and soil fertility of onion (Allium cepa) grown with beef cattle manure compost (CMC) under a reduced rate of chemical fertilizer for sustainable production in the 2006–07 growing season. Chemical fertilizer application rate was reduced to a third of the recommended rate of nitrogen (N), phosphorus (P), and potassium (K). Treatments consisted of five levels of CMC (0, 20, 40, 60, and 80 Mg·ha−1). There was a significant increasing effect on growth and yield parameters by applying CMC compared with 0 Mg·ha−1. In addition, there was also a significant increasing quadratic effect on yield on increasing CMC rates from 0 to 80 Mg·ha−1 with an R 2 of 0.46. Maximum marketable yield was 62.7 Mg·ha−1 at 40 Mg·ha−1 CMC, which was due to increased stand reduction and unmarketable bulbs as well as decreased bulb weight at higher rates of CMC. The CMC rates had no effect on bulb dry weight and N or P concentration in the bulb and leaf. Furthermore, there was an increasing linear effect on soil pH, and organic matter (OM), available P, and exchangeable cations throughout vegetative growth and at harvest. We concluded that the excessive application of CMC did not affect onion yield and accumulated soil fertility.

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The effect of nitrogen (N), phosphorus (P), and potassium (K) supply on the growth and nutrient uptake of intermediate-day onions (Allium cepa L.) was investigated in a double cropping system of rice and onion in which rice straw had been annually applied. The experiment consisted of three sets of treatments: N (0, 120, 240, 360 kg·ha−1 N), P (0, 18, 35, 52 kg·ha−1), and K (0, 67, 133, 200 kg·ha−1) with the addition of 8.0 t·ha−1 of decomposed pig manure. The rice straw was incorporated with tillage after harvest. Foliage weight of the onion plant was affected by N rate on 21 Apr. and on 23 May. Bulb weight was also influenced by N rate on 23 May and at harvest. The only difference (P ≤ 0.05) in onion yield was observed between the zero N rate and all the other N levels. Soil pH was correlated with rate of N fertilization. Soil NO3-N for 240 and 360 kg·ha−1 N rates ranged from 36.6 to 113.7 and 49.9 to 148.6 mg·kg−1, respectively, which was at least twice as high as that at 120 kg·ha−1 N rate. The highest fertilizer use efficiency of nitrogen was 36.0% at 120 kg·ha−1 followed by 240 kg·ha−1 at 28.0% and 360 kg·ha−1 at 20.6%. There was no clear effect of P or K rates on P or K concentration in the onion bulbs. K concentration and uptake in the onion leaf tissue increased with higher K rates. In conclusion, compost and rice straw provided sufficient P and K to grow onions without additional P and K fertilizer, and under these conditions, the fertilizer level of 120 kg·ha−1 N produced as much onion bulb yield as higher N levels.

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This study aimed to compare agricultural practices, soil physical and chemical properties, growth characteristics, and nutrient uptake of bulb onions from organic and conventional farms in southeastern Korea during the 2011–12 growing season. Soil and plant samples were collected from eight certified organic fields managed organically for more than 5 years and eight conventional fields adjacent to the organic fields. The amounts of nutrients applied to onion fields were approximately two times greater with the conventional methods than with organic methods. However, the soil physical and chemical properties were not significantly different between the organic and conventional systems, except for NO3-N in early May. Growth characteristics were significantly different in early April with organic bulb yield of 55.9 t·ha−1, which was 21.8% lower than conventionally produced onions. Yield reduction in organic onions was the result of lower large-sized (8 cm or greater) bulb yield compared with conventional production. In the conventional system, phosphorus (P) and potassium (K) content of leaf tissue in early April, and nitrogen (N) and P content of bulb tissue in early May were higher than those in the organic system. Uptake of all nutrients was greater in the conventional onions compared with the organic onions, except for leaf tissue at harvest. In conclusion, organic onions began to grow and absorb soil nutrients later than the conventional onions in the initial vegetative growth stage. Moreover, it led to an organic onion producing a lower bulb yield. To accelerate the initial growth of the organic onion plant, agricultural practices need to be modified. Modifications that may help include using larger sized seedlings at transplanting, covering the plants with nonwoven fabric or transparent plastic film to increase warmth during winter, and harvesting the onions 1 week later than the conventional onions.

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This study evaluated the effects of a nonwoven polypropylene (NPP) covering during overwintering with different mulch types and transplant times on bulb onion growth and yield of intermediate-day onions (Allium cepa L.) during the 2015/2016 and 2016/2017 growing seasons. Field experiments were conducted using a split-split plot design with three replicates. Treatments included main plots containing different mulch types (transparent plastic mulch, black plastic mulch, or bare ground), subplots with different transplanting times (20 Oct., 5 Nov., and 20 Nov.), and sub-subplots containing two onion cultivars (Sunpower and Katamaru). NPP was used to cover all plots on 1 Dec., and it was removed on 28 Feb. Mean daily air temperatures during transplanting and root establishment were 2.6 °C higher during the 2015/2016 growing season compared with the 2016/2017 season. NPP covering on bare ground increased soil temperature by 2.1 °C compared with no treatment. Soil water potential with transparent and black mulches and NPP continued to be more than −10 kPa until early March. Number of leaves, and root and leaf weight were significantly greater during the 2015/2016 growing season than during the 2016/2017 growing season; there were also significantly greater for onion plants grown with transparent plastic mulch than for those grown with black plastic mulch or no mulch on 4 Apr. and 5 May. Marketable bulb yield was lower during 2015/2016 (32.0 Mg·ha−1) than during 2016/2017 (38.5 Mg·ha−1); this was due to the increased unmarketable bulb yield, with 33.2 Mg·ha−1 bolters and 3.9 Mg·ha−1 doubled bulbs during 2015/2016 compared with 3.9 Mg·ha−1 bolters and 0.3 Mg·ha−1 doubled bulbs during 2016/2017. Marketable bulb yield of ‘Katamaru’ (38.9 Mg·ha−1) was greater than that of ‘Sunpower’ (31.6 Mg·ha−1). Marketable bulb yield increased with later transplanting times, and onions grown with black plastic mulch achieved the highest bulb yield (43.0 Mg·ha−1), followed by transparent mulch (34.7 Mg·ha−1) and no mulch (28.0 Mg·ha−1). When the temperatures from early November to early December were similar to the 30-year average temperatures, marketable bulb yield could increase with the NPP covering, especially for onions grown with black plastic mulch or no mulch when transplanted from late October to early November.

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