Conservation Agriculture Research Updates - May 2024

This article reports the results of evaluation of new wheat cultivars in on-farm conditions using different tillage systems. There were 7 wheat cultivars (3 bread wheat and 4 durum) and 3 tillage systems; conventional (CT), reduced (RT), and No-Till (NT) in two locations for 3 cropping seasons. Overall the CT treatment had the highest yield and NT the lowest. But maybe that was because there was no residue mulch or there were problems with the NT equipment or soil moisture at planting. NT needs a higher soil moisture at seeding that a CT soil. However, there were differences in yield between the different cultivars by tillage. Some cultivars had better yield under CT and others under NT. The experiment needs to look at cultivars by tillage with and without residue and plant the NT when the moisture is higher and not wait for the CT plots to be planted.

This paper starts by saying that although CA facilitates build-up of SOC, the sequestration potential of arable soils is affected by edaphic factors and is not well understood. The research used an on-farm approach with pairwise comparison of 21 conventional vs highly innovative ‘pioneer’ farms across a wide range of arable soil types and evaluated the leverage of site attributes and management practices such as crop diversity, reduced tillage, organic fertilization, cover cropping and inter cropping on the SOC sequestration potential. While most pioneer management practices proved beneficial for the sequestration of SOC – particularly cover cropping and crop diversity – our results clearly show that soil texture was the most significant shaping factor. Coarse-textured soils had a significantly higher potential for SOC accrual compared to medium- and fine-textured soils. The initial SOC content also had a significant effect on prevalent sequestration potentials. They conclude that carbon farming schemes need reconsideration within the state-of-the-art scientific framework of carbon saturation behavior in order to properly account for biophysical constraints when formulating soil-related climate change mitigation policies. 

This paper provides an overview of tillage in Hungary. Interestingly, they say interest in CA dates back 120 years, although significant changes did not occur until the last 50 years. Progress was driven by the need to protect soil, the opportunity to raise farming standards, and the need to mitigate climate-related threats. Since the average yield in Hungary was usually sufficient for the domestic need, the main objective of crop production was to avoid yield loss. This study utilized long-term experimental data and monitoring results. The experiences and first results in no-till and strip-tillage showed that difficulties can be reduced by identifying site-specific technology solutions. They suggest that the need for subsoiling is not a matter of debate nowadays but rather the timing of operation and the investigation of the duration of the effects. The area of plowed soils has decreased recently, but improved implementation by farmers is required.

Upland rainfed rice in Madagascar is usually planted on tilled soil as seed and not transplanted resulting in serious weed issues. This field experiment looked at a no-till system with the legume Stylosanthes (NT) managed as a living mulch and compared with the tilled (CT) system. In addition two fertilizer treatments were added; organic manure (F1) and organic combined with mineral fertilizer (F2). Weeds flora were documented and the affect of weeds on rice yield assessed by having weedy and weed-free plots. The effect of the cover crop on rice yield was also assessed using weed-stylosanthes-free plots. Results showed that NT suppressed the dominant grass weeds leading to a decrease in total weed biomass. Rice yield was significantly higher in NT than in CT. The living mulch reduced rice yield by 14% but it remained significantly higher in NT than in CT. The addition of mineral fertilizer to the organic manure had a positive effect on rice yield but only in weed-free conditions.

This paper from New Zealand looked at various tillage options with and without irrigation on SOC, fungal biomass and their relation to to soil aggregate sizes in a 14-year experiment. They hypothesized that long-term irrigation and intensive tillage would negatively affect soil aggregation. The experiment was started in 2003 and data taken in 2017. Two tillage treatments were intensive tillage (IT) to 20-25cm compared with no-till (direct drill - DD) and irrigation was sprinkler and none (rainfed). Soil samples (0-5 cm layer) were analyzed for pore size distribution, specific surface area and microbial biomass. Sieving was also used to separate macro- (LM) and micro-aggregates (SM), particle sized silt + clay and fine particles. Both DD and rainfed management increased total SOC content of the bulk soil. The LM and its SOC increased in DD compared to IT. A higher fungal:bacteria (F:B) ratio was generally accompanied by a greater LM fraction and mean weight aggregate diameter, highlighting the importance of fungi in the formation of LM. They concluded that detrimental effects on soil aggregation by tillage and irrigation was not conclusive and a longer study period is needed to confirm.

Morocco is experiencing threats to food security due to climate change  as temperatures rise and precipitation declines. CA is considered as a way to help. This research compared and evaluated the impact of four cultivation techniques (no-till: NT, minimum till: MT, chisel ploughing: CP and deep ploughing: DP) on certain physiological and agronomic parameters of bread wheat. NT showed the highest grain yield, and water use efficiency (WUE) compared with other cultivation practices.

This study looked at different tillage systems (NT vs moldboard (CT)) with 4 fertilizer regimes (None (CON), NPK (MIN), Compost (ORG), & NPK + Compost (MIX) on SOC and microbial biomass 20 years later. The abundance of the microbial community and N-functional guilds within the soil profile (up to a depth of 60 cm) was also determined. SOC was higher in NT than CT at 0-10 cm depth. Organic fertilization increased SOC in both tillage treatments to 20cm. Microbial biomass decreased with depth due to a decrease in SOC, and, consequently, were higher in NT than in CT, in the top 20 cm soil for microbial biomass and bacterial abundance and top 10 cm for fungi and archaea. They conclude that their study provided  insights that can aid in development of effective strategies for steering soil microbiome responsible for N2O emissions.

This interesting paper looks at what happens when smallholder farmers adopt labour and money-saving practices such as no-till to the livelihoods of these farmers. They used qualitative photovoice methodology on 25 South Asian households to address this question. They identified activities related to agricultural and livelihood diversification that were linked to resilience, satisfaction and better livelihood outcomes. They suggest that cereal system intensification is synergistic rather than antagonistic to crop and livelihood diversification. They conclude that this participatory human focused method that looks at people rather then plots helps identify a diversity of livelihood strategies.