Quantifying the Relationship between Leaf Nitrogen Content and Growth Dynamics and Yield of Muskmelon Grown in Plastic Greenhouse

Abstract

<jats:p>The aim of this study was to quantitatively investigate the impacts of nitrogen on growth dynamics and yield, so as to facilitate the optimization of nitrogen management for muskmelon crop in plastic greenhouse. For this purpose, four experiments with different levels of nitrogen treatment and planting dates on muskmelon (<jats:italic>Cucumis melo</jats:italic> L. ‘Nanhaimi’ and ‘Xizhoumi 25’) were conducted in plastic greenhouse located at Sanya from Nov. 2012 to Sept. 2014. The quantitative relationship between leaf nitrogen content and growth dynamics and yield of muskmelon was determined and incorporated into a photosynthesis-driven crop growth model (SUCROS). Independent experimental data were used to validate the model. The critical leaf nitrogen content at flowering stage for muskmelon ‘Nanhaimi’ and ‘Xizhoumi 25’ were 19.8 and 21.0 mg·g<jats:sup>−1</jats:sup>. The coefficient of determination (<jats:italic>r</jats:italic><jats:sup>2</jats:sup>) and the relative root-mean-squared error (rRMSE) between the predicted and measured value of growth dynamics and yield were, respectively, 0.91 and 10.8% for leaf area index (LAI), 0.90 and 19.6% for dry weight of shoot (DWSH), 0.76 and 30.3%, 0.82 and 21.1%, and 0.92 and 11.9% for dry weight of leaf (DWL), stem (DWST), and fruit (DWF), 0.91 and 17.3%, 0.89 and 13.9%, 0.86 and 27.8%, and 0.88 and 20.6% for soluble sugar content (SU), soluble protein content (PR), vitamin C content (VC), and soluble solids content (SO) of fruit, and 0.90 and 10.1% for fresh weight of fruit (FWF). The model could be used for the optimization of nitrogen management for muskmelon production in plastic greenhouse. Further calibration and test would be needed during the application of the model in wider range of conditions and muskmelon cultivars.</jats:p>

Effects of Leaf Potassium Content on Growth Dynamics of Muskmelon and Developing a Coupling Model of Nitrogen and Potassium

“…The requirement of available potassium for 'Xizhoumi 25' was less than 'Nanhaimi' to their critical value of leaf potassium content at flowering stage. This is contrary to our previous study on the effect of nitrogen fertilizer on melon (Yang et al, 2015), the change of leaf nitrogen content had a greater impact on the parameter values of 'Nanhaimi', and the requirement of available nitrogen for 'Nanhaimi' was less than 'Xizhoumi 25'. This can be attributed to the fact that different varieties had different characteristics of fertilizer demand.…”

“…Two ways of nitrogen and potassium coupling (multiplicative coupling and minimum coupling) were compared in this study, and the result showed that calculated value of growth parameters of multiplicative coupling is closer to the measured value than minimum coupling, but not for the quality parameters. The main reason might be because the effects of nitrogen and potassium on quality parameters is opposite, the effect of nitrogen on most quality parameters is negative [parameters decreased with the increase of leaf nitrogen content (Yang et al, 2015)], but the effect of potassium is positive on these quality parameters (parameters increased along with the leaf potassium content), and that would limit the curve-fitting effect of multiplicative coupling on quality parameters. In this study, just one coupling way was applied in the model development.…”

“…where X(0) is the value of P g,max , LAImax, rLAI, PISH h , rPISH, PIL h , rPIL, PIF h , rPIF, PTIb, rSU, rPR, rVc, and rSO while the leaf nitrogen and potassium content at flowering stage were saturated, and the value of these parameters of 'Nanhaimi' were 21.2, 4.2, 0.07, 0.981, 0.003, 0.135, 0.071, 0.797, 0.061, 79.6, 0.023, 0.024, 0.026, and 0.029, respectively, and were 23.3, 3.5, 0.061, 0.966, 0.004, 0.155, 0.07, 0.818, 0.051, 65.6, 0.024, 0.024, 0.024, and 0.029, respectively, for 'Xizhoumi 25'; rXN and rXK are the increasing rates of these parameters along with the leaf nitrogen and potassium contents at flowering stage [Yang et al (2015) and Table 3].…”

“…where LA (m 2 ) is the leaf area, LL (m) is the leaf length, k is the empirical coefficient [0.62 and 0.59 for 'Nanhaimi' and 'Xizhoumi 25', according to Yang et al (2015)], LAI Fig. 6.…”

Phthalanilic Acid with Biostimulatory Functions Affects Photosynthetic and Antioxidant Capacity and Improves Fruit Quality and Yield in Cowpea (Vigna unguiculata (L.) Walp.)

“…At the seedlings (5-6 true leaves), full-bloom, and early podding stage, fully-expanded mature leaves (the upper third leaf) of cowpea were measured on sunny days, and results were collected from five randomly selected plants for each plot. In the course of measurement, saturating light intensity was kept at 1500 mmol•m −2 •s −1 , and three readings (1-min interval for each reading) were recorded averagely to make the measurement stability and precision [37]. Data were reported as the mean value of three replicates (five seedlings per replicate) for each treatment.…”