Speaker
Description
Introduction
The use of intercrops has started to gain interest amongst farmers, particularly those practicing organic or agroecological principles, as this approach is known to help maintain crop yields under reduced input conditions through improved resource use efficiency and can help limit yield variation across seasons associated with unusual weather patterns. Some national Governments are also starting to become aware of the use of intercrops, particularly those Governments with policies striving to achieve Net Zero at some point in the future. Much of the research on intercrops to date has focussed on the season the intercrops are grown, but legacy effects on soil and following crops in the rotation are less well known (Pappa et al. 2012). This paper focuses on some of these legacy effects based on the growth of a spring barley crop cultivated on the same plots used to grow a range of grain legumes as either sole crops, or in a mixture (intercrop) with spring barley the previous year.
Materials & Methods
A range of grain legumes were established in both 2019 and 2020 in Aberdeenshire, Scotland (UK) in replicated small plot (1.5m x 12m) field trials. The same crops and seed ratio treatments were used in each year and the soil was a sandy loam with moderate P and K indices and a pH of around 6.0. Crops included spring barley (var. Westminster) as a control treatment, as well as green lentil (var. Anicia) at 2 densities (both with a spring oat supporting crop sown at 20kg/ha), field beans (var. Fuego) as either a sole crop, or as an intercrop with spring barley in a 40:60 or 60:40 ratio of the recommended seed rate for each crop species. Similar sole crop and intercrop ratios (with barley) were also used for peas (var. Zero 4) and lupins (var. Iris). In 2020 and 2021, i.e. the years following the sole crop and intercrop cultivation, the pre-crop effect of those treatments were evaluated by superimposing a spring barley crop onto the same plots and taking this through to harvest with a small plot combine. At establishment, half of each plot (5m x 1.5m) received no N fertiliser and the other half received 60kg N/ha. P and K were applied across the whole trial area at recommended rate. A range of assessments and measurements were taken, but the focus here is on the combine yield of the follow-on spring barley crops, particularly the average yield across both years to indicate consistency of performance across seasons (Fig. 1).
Results & Discussion
Figure 1: Average yield of two spring barley crops grown in consecutive years (2020 & 2021) after the same pre-crop treatments, including a spring barley sole crop, and grain legumes grown as sole crops or as intercrops with spring barley. These were grown with zero N, or with an application of 60 kg N/ha. Error bars represent standard error of the mean (n=4).
In almost all cases, the addition of 60 kg N / ha resulted in a significant elevation in yield compared to the same pre-crop with no N applied and generally had lower variability (smaller error bars). ANOVA performed on the spring barley averages from both years for the Zero N treatments indicate significant yield increases (P≤ 0.001) compared to the barley pre-crop control, with least significant difference (LSD) indicating any yield above 5t/ha was statistically greater than the control. The lentils, sole crop beans and beans intercropped at the higher ratio, sole crop peas and sole crop lupins all achieved an improved legacy yield. The other pre-crop treatments showed no yield increase but may have provided other benefits not highlighted in this paper.
References
PAPPA VA, REES RM, WALKER RL, BADDELEY JA, WATSON CA. Legumes intercropped with spring barley contribute to increased biomass production and carry-over effects. The Journal of Agricultural Science. 2012;150(5):584-594. doi:10.1017/S0021859611000918
| Keywords | Grain legume; Intercrop; Legacy effect; Spring barley; Yield |
|---|
