# Improving Nitrogen and Water Use Efficiency in Intensive Cropping by Optimized Management and Crop Rotations

## TL;DR

This study shows how optimized crop rotations and management practices can improve nitrogen and water use efficiency while maintaining crop yields and profits in intensive farming.

## Contribution

The paper introduces optimized crop rotations and management strategies that enhance resource efficiency and sustainability in intensive cropping systems.

## Key findings

- Optimized treatments increased nitrogen use efficiency by 19–41% and water use efficiency by 13–20%.
- The ONM/WM treatment provided the highest economic benefits and a comprehensive evaluation index of 0.66.
- ON/WMM and ON/GM treatments reduced water use but had lower yields and profits.

## Abstract

Nitrogen (N) and water are key resources for crop production and improving the efficiency with which they are used remains a major global challenge in intensive cropping systems. Here, we report how crop yield, N and water use efficiency, N surplus, and economic benefits can be improved from optimized management and crop rotations. A conventional winter wheat–summer maize double cropping (CN/WM) rotation in a three-year field experiment in the North China Plain is compared with alternative optimized rotations. The first three optimized treatments were wheat–summer maize rotation with optimized N and irrigation rates, tillage and straw management (ON/WM), and partial manure substitution (ONM/WM) or biochar addition (ONB/WM); the fourth optimized treatment was winter wheat–summer maize–spring maize producing three harvests in two years (ON/WMM); and the last was spring maize incorporating green manure during the fallow season for one harvest per year (ON/GM). The results showed that the ON/WM, ONM/WM, and ONB/WM had comparable yields to CN/WM, but significantly increased N use efficiency by 19–41% and water use efficiency by 13–20% and reduced N surplus to 353–531 kg N ha−1 2yr−1. From these three optimized treatments, the ONM/WM performed better, with a comprehensive evaluation index of 0.66 and the highest economic benefits. The ON/WMM and ON/GM treatments also significantly increased N and water use efficiency but resulted in relatively low crop yields and profits; nevertheless, they significantly reduced water use and are suitable for water saving cropping systems. We concluded that optimized management-combined manure with synthetic N fertilization in wheat–summer maize rotations can achieve high crop productivity, environmental, and economic benefits, which contribute to a more sustainable crop production.