Climate and landscape mediate patterns of low lentil productivity in Nepal

the 1st week of November (Fig 2B). This suggests that the risks posed by Stemphylium blight can be greatly reduced through earlier planting in October. Discussion Although development efforts in Nepal have highlighted the importance of pulse crop intensi- fication to food, nutritional, and income security, our results confirm that lentil remains a risky enterprise with survey data from two seasons highlighting the prevalence of crop failures (16%), modest yields (353 kg ha-1), and low levels of profitability (US$ 33 ha-1), particularly in wet winters. Nevertheless, site factors such as drainage class influence responses with upland sites performing well in wet winters and lowland sites performing well in dry winter (S3 Fig). The dominant production area for lentil in Nepal is in the Terai plain where poorly drained conditions are common. Lentil is particularly sensitive to the direct effects of waterlogging and moisture deficit dur- ing flowering and pod-filling stage [48,78]. Although available soil moisture and rainfall are important for lentil production in South Asia, waterlogging in lentil also damages the root sys- tems thereby limiting crop capacity for water uptake when conditions become drier [79]. Per- haps more importantly, significant negative effects of high rainfall can increase disease severity, particularly for fungal diseases [80]. In our study, 78% of farmers reported significant disease incidence in their fields in the comparatively wet winters of 2014 and 2015 (Table 1)

and disease incidence had a large negative impact on lentil production (Table 3). While, some wilt-related diseases are prolific when there is drought [81], other blight and fungal diseases are more prominent when there is high moisture in the soil and the broader environment [82,83]. Due to increasing winter precipitation levels in Nepal, the fungal disease Stemphylium blight has become a serious threat [49,50]. High and stable yields of lentil are only likely to be achieved in Nepal when the threats posed by diseases mediated by winter rainfall are effectively and economically managed. Fig 2. Stemphylium blight simulations with the stempedia model with 30 years of historical weather data: A) severity across years, B) severity across years as a function of planting time. https://doi.org/10.1371/journal.pone.0231377.g002 PLOS ONE Climate and landscape mediate low lentil productivity PLOS ONE | https://doi.org/10.1371/journal.pone.0231377 April 16, 2020 13 / 19