Abstract
Estimating balanced nutrient requirements for a watermelon plantation is essential to increase its fruit yield and nutrient use efficiency. This is vital for China, which produces 60% of world’s watermelons with excessive fertilizer application. Therefore, datasets between 2000 and 2019 from field experiments in major watermelon producing regions across China were collected to assess relationships between fruit yield and nutrient uptake, and to estimate nitrogen (N), phosphorus (P), and potassium (K) requirements for a target yield using a modified Quantitative Evaluation of the Fertility of Tropical Soils (QUEFTS) model. The results showed that the QUEFTS model predicted a linear increase in fruit yield to 60–70% of the total potential yield when balanced amounts of N, P, and K nutrients were absorbed. To produce 1000 kg of watermelon, 2.11 kg N, 0.27 kg P, and 2.69 kg K were required in shoot, and the corresponding internal efficiencies (IE) were 475, 3682, and 372 kg fruit per kg of N, P, and K, respectively. The modified QUEFTS model also simulated a balanced N, P, and K removal by fruit (accounting for 50.9%, 58.2%, and 66.4% of these nutrient accumulations in shoots, respectively). Field validation experiments further verified that the modified QUEFTS model could be used for estimating balanced nutrient requirements. Results from this study can provide practical guidance on fertilizer recommendations for improving fruit yield while preventing excessive or deficient nutrient supplies in China’s watermelon plantations.
Highlights
Watermelon (Citrullus lanatus (Thunb.) Matsum. et Nakai), one of the most important fruit crops, is widely cultivated and consumed around the world due to its juicy, sweet, taste and low price.Watermelon is abundant in beta-carotene, lycopene and polysaccharides, and is a source of antioxidants, which can be applied in the pharmaceutical and cosmetic industries [1,2,3]
The fruit yield of watermelon ranged from 6.48 t/ha to 99.1 t/ha, with an average of 46.7 t/ha (Table 4)
The reason for these significant differences was the diversity of watermelon varieties, climate, and field management [50,51]
Summary
Watermelon is abundant in beta-carotene, lycopene and polysaccharides, and is a source of antioxidants, which can be applied in the pharmaceutical and cosmetic industries [1,2,3]. Both the planting area and Agronomy 2020, 10, 1776; doi:10.3390/agronomy10111776 www.mdpi.com/journal/agronomy. Agronomy 2020, 10, 1776 yield of watermelon in China have ranked first in the world for decades, and the total production is still increasing. To pursue higher yield and greater economic benefit, more and more fertilizers have been applied in watermelon plantations by Chinese farmers, resulting in a declining trend of fertilizer use efficiency in China [5].
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