Effects of Lucerne Removal Time on Soil Water and Productivity in a Lucerne- Wheat Rotation on the Western Loess Plateau

Abstract

Rainfed spring wheat (Triticum aestivum L.) is the most important cereal crop on the Western Loess Plateau. Lucerne (Medicago sativa L.) has been very popular. There are problems associated with both continuous cropping and with perennial lucerne systems. The key challenge for rain-fed cropping systems is to adopt strategies that make optimal use of water. Developing lucerne-wheat rotation systems will have significant benefits for agriculture development on the Loess Plateau, nevertheless, it is very important to terminate lucerne at the right time as it affects soil moisture. However, very little research has been done on the timing for termination of old lucerne in the semiarid areas of the Western Loess Plateau. Based on field experiments conducted in a typical semiarid area on the Western Loess Plateau, this paper aimed to investigate the soil water and termination timing of 30 years old lucerne on the productivity of lucerne-wheat rotation. The results showed that the soil profile after long-term lucerne was very dry down to 3 meters, the three year experiment period was not sufficient to allow soil water recharge, even after a high rainfall year. Time of 30 years old lucerne removal (in spring or later in the year) had no significant effect on soil water regimes. As a result, weeds became more competitive, the old lucerne stand showed poor dry matter, yield, had no response to 1 kg ha-1 of N application, and was overdue for termination. Following spring wheat made no response to 1 kg ha-1 of N fertilizer due to dry soil profile after 30 years lucerne growing.