Investigation of grain postharvest technologies and systems for managing climate-related risks in smallholder farms of shire valley, southern Malawi.

Abstract

The world’s climate is changing. Increasing temperatures and incidence of dry spells and droughts are projected to continue into the next century. These factors will negatively affect household (HH) food security, crop production and pest problems, including storage insect pests and the performance of storage technologies. A study to evaluate maize postharvest management options was conducted to help farmers strengthen the climate-resilience of their HH food security strategies. The work began with a survey using structured and semi-structured questionnaires and checklists to learn about the postharvest systems and climate-related experiences of farming HHs in Shire Valley, southern Malawi. The results showed that food insecurity in Shire-Valley was perceived to have increased in the last 10-20 years due to crop failure, and most HHs (~65 %) thought the mean ambient temperature had increased during that period. Many respondents (~42.9 %) reported an increased usage of synthetic pesticides compared to 10-20 years ago due to a perceived increase in insect pest pressure. These findings emphasised the need for urgent implementation of increased awareness-raising and training in improved postharvest management in the face of global-warming. Following the survey, farmer-managed participatory trials were conducted comparing existing and newly-introduced storage technologies over a 32 week period in two consecutive seasons. The seven treatments were Neem leaf powder (NM), Actellic Super dust (ASD), ZeroFly® storage bag (ZFB), Purdue Improved Crop Storage bag (PICS), Super Grain Bag (SGB), metal silo (MS) and untreated grain in a polypropylene bag (PP). The trials showed that the storage technology choice and duration significantly affected the level of insect grain damage and the number of insect pests, and that the level of pest attack can differ significantly between seasons. Hermetic bags (PICS, SGB) kept storage insect infestation low for up to 32 weeks, and were more effective than the ASD, NM, or PP. The study recommended the use of PICS and SGB for long-term grain storage. To examine the effect of higher ambient temperatures on the efficacy of maize grain storage protectants and facilities, two laboratory trials were conducted. Experiment I compared five grain protectants [Actellic Gold dust (AGD), Shumba Super dusts (SSD), Wivokil Super dust (WSD), NM and wood ash (WA)] admixed with maize, while experiment II assessed four facilities (PICS, SGB, MS and PP) using untreated maize. Both experiments ran for 12 weeks using climate chambers set at 32 °C and 38 °C, and mean ambient temperature (26 °C). Significantly higher grain damage and weight loss occurred in the non-synthetic (NM, WA) than synthetic protectants (AGD, SSD, WSD) at all experimental conditions. The hermetic containers (PICS, SGB, MS) kept mean insect grain damage below 6.4% compared to 24.5% in the untreated control at all the experimental conditions. These findings imply that the efficacy of synthetic grain storage protectants and hermetic storage containers may not be negatively affected by warmer temperatures (32 °C or 38 °C). Warehouse receipt systems (WRS) and community grain banks (CGB) are being promoted in SSA to reduce grain storage losses and improve market access and food security. However, no information on their potential as adaptation strategies in climate change (CC) prone areas existed. Interviews with WRS and CGB managers and beneficiaries, and rapid loss assessment methods were used to learn about the systems and analyse grain weight loss during a 24-week period. Grain deposits ranged from 0.1 and 15 mt per depositor, and quantities of maize produced and deposited were correlated. Weight loss of maize and pigeon peas in WRSs were less than 4.6 % and 9 % respectively. In conclusion, food insecurity has increased in Shire Valley, mainly contributed by climate change. The PICS and SGB are recommended for use by farmers for grain storage in Shire Valley including SSA. Results suggest farmers can continue to use SGB, PICS and MS, or AGD, SSD and WSD for stored maize protection as temperatures increase in CC-prone areas. The WRSs and CGBs could act as grain reserves for use during climate-related events and play a role in the distribution of emergency relief food to the affected HHs.