Optimization of apple irrigation and N fertilizer in Loess Plateau of China based on ANP-EWM-TOPSIS comprehensive evaluation

Abstract

It is imperative to scientifically and credibly optimize the irrigation and nitrogen (N) fertilizer level of apple orchards in Loess Plateau, where is water-scarce and over-fertilized with N. In 2017-2018, four irrigation levels (W1, rainfed; W2, 60% ETc; W3, 80% ETc; W4, 100% ETc) and four N fertilizer levels (N1, 375 kg·ha−1; N2, 490 kg·ha−1; N3, 605 kg·ha−1; N4, 720 kg·ha−1) were applied to investigate the response of apple yield, quality, water use efficiency (WUE), partial factor productivity (PFP) of N, economic benefit and N balance to irrigation and N managements. The results proved that irrigation and N managements could improve apple yield, quality, WUE, PFP, economic benefit and N surplus. The highest apple yield, Chroma, Vitamin C (VC), PFP and economic benefit were obtained by 80% ETc in different irrigation levels. High N levels significantly increased apple yield, Chroma, VC, WUE and economic benefits. However, excessive irrigation and N could cause negative effects. 100% ETc reduced firmness, titratable acid and WUE. High N levels not only increased N surplus but also decreased firmness, shape index, titratable acid, soluble sugar and PFP. Clearly, the optimal irrigation and N managements were varied for apple yield, quality, WUE, PFP, economic benefit and N surplus. Therefore, an integrated model based on Analytical Network Process (ANP), Entropy Weight Method (EWM) and TOPSIS was used to comprehensively evaluate the multi-objectives of apple cultivation in Loess Plateau. It was concluded that the irrigation (1500-1800 mm) and N levels (540-660 kg·ha−1) were recommended for improving apple cultivation in this region. Our results played an important role in guiding irrigation and N management of apple cultivation in Loess Plateau of China.