Conservation Agriculture Research Updates - September 2024

This chapter in this reputable book discusses the issues of urbanization, soil degradation, and inappropriate farming practices and the pressure that results on soil, water,and vegetation and subsequently food and nutritional security, and at the same time providing ecosystem services and meeting the Sustainable Development Goals (SDG's). They discuss the role of No-till (NT) and Conservation Agriculture (CA) is reversing these negative trends. They cite long term experiments that provide information on improving soil health, SOC sequestration, GHG emissions, climate change mitigation, and resource use efficiency all impacting future food security. This chapter discusses the effect of NT/CA on soil health, nutrient stratification, SOC dynamics through modeling, SOC sequestration, GHG emissions, socio-economic condition in adoption and also suggesting the future perspectives on NT and CA.

This paper explores the performance of cropping systems with different legume diversity on maize productivity in Zambia and determine the minimum land required to reach maize self sufficiency at the household level using the different systems. Six maize-based cropping systems, comprising maize monocropping, maize-legume rotations and intercrops under ‘conventional’ tillage and conservation agriculture, were evaluated across 40 farms in Zambia. The results are provided in this paper. They conclude that introducing legumes into their maize systems can increase yields of maize and intercropping legumes can be used in land restricted farms.

This paper looks at nitrous oxide (N20) emissions in relation to soil pores under long term CA practices. Soil cores were extracted from CT and NT plots and cover crop (CC) hairy vetch (HV) and no CC (NV) and used for N20 measures. Their results show CT and HV emitted more N20 than NT or NV and for macroporosity, NT and NV increased these more than CT and HV. They conclude that N2O emissions were positively and significantly correlated to relative soil gas diffusivity, CT-derived macroporosity, number of macropores, and fractal dimension.

CA and regenerative agriculture (RA) are proposed as methods to slow down soil degradation in South African agriculture. This research attempts to find out if CA/RA are financially viable. They compared the returns from CA/RA over a 20-year period against CT and just NT. They found that the cumulative free cash flow (CFCF) of the average between the realistic and conservative CA/RA scenarios in year 20 was considerably higher than that of the other systems under investigation and conclude that the CFCF difference of CA/RA compared to other systems represents a financial opportunity cost of not converting to the CA/RA system.

Strip tillage is gaining a lot of attention from farmers in the USA so I chose this article from a study in the USA (Alabama following Cotton) for readers of my CA newsletter. The objective of their study was to assess the effects of different tillage practices including strip tillage on soil pore properties. Undisturbed soil columns were collected during two seasons comparing ST with CT. Overall the study showed taht pore morphology can be affected by tillage and seasonal aspects associated with them.

This is a second 2022 article on cover crop benefits. It focuses more on replacement of summer fallow with cover crops in semi-arid regions and proposes this benefits soil health. It looked at the effects of long-term CC in no-till winter wheat - grain sorghum -fallow system. Fallow replacement treatments were spring-planted and included peas for grain as well as one-, three-, and six-species CC mixtures compared with summer-fallow. Half of each CC treatment was harvested for forage and the other half remained standing after termination. They conclude that simple CC mixtures and CCs managed for hay provide similar soil benefits as diverse CC mixtures or CCs left standing in this semi-arid environment.

This paper looks at the impact of CA on the soil microbial community under rainfed conditions in Spain. They compare soil bacterial changes in relation to tillage practices. The experiment was sampled from 0-15 cm depth after 19 years of minimum tillage (MT) and no-till (NT) practices, along with rotation. They show that sampling time and tillage affected the bacteria community, the crop had little effect. May had more bacterial diversity than December. NT was found to significantly decrease bacterial diversity compared to MT. They conclude that after 19 years, NT did not promote bacterial diversity in the upper soil layers.

This paper is a literature review of meta-analyses dealing with the implementation and performances of CA in France. They suggest that past CA research focused on productivity and soil quality when in fact other issues like biodiversity and profitability are mentioned less. An online survey showed that 63% of respondents thought that CA helps reduce pesticide use, 91% that CA improves water use efficiency, and 77% that CA helps to store carbon and achieve the objectives of the 4 per 1000 international initiative. The authors suggest that the definition for CA be moved to performance-based metrics that address different ecosystem services. Issue like climate change, biodiversity loss, water pollution are some suggestions.  

Nearly 80% of annual crops in Parana State, Brazil use NT and NT systems (NTS). In addition to NT, NTS sites permanently include: minimum soil disturbance, soil cover (straw and living vegetation) and crop rotation and diversification with cover crops. This paper reviews the soil health of NTS related to earthworm populations. Data from 130 sites with NT or NTS, located in 29 counties, of which 93 had biomass and 91 had species richness data, were used to identify the age of these practices on earthworm populations. Abundance was significantly higher in NT than NTS in the initial phase of adoption, and both abundance and biomass decreased with increasing age of NT. Most sites had poor or moderate SH suggesting that improved management is needed to promote earthworm numbers.

This paper states that the future of the rice-wheat system, a major food security system for South Asia is at stake because of "Traditional practices like conventional tillage (CT) residue burning, and indiscriminate use of groundwater with flood irrigation". As such this paper studies the role of CA, mungbean integration, water, N, and energy use efficiency in the RW system. The results showed that bundling CA with subsurface drip irrigation (SDI) saved substantial water in both rice and wheat compared to traditional farmer practice. Based on the 3-year mean, CA with SDI (mean of Sc5–Sc8) recorded −2.5% rice yield, whereas wheat yield was +25% compared to farmers practice and rice and wheat yield under CA with flood irrigation were increased by +7 and + 11%, compared to their respective CT practices. Mungbean integration added 26% to productivity. They concluded that CA with SDI for precise water and N management proved to be a profitable solution to address the problems of groundwater, residue burning, sustainable intensification, and input (water and energy) use with the potential for replication in large areas.

This article starts out by saying farmers growing rice-wheat in the Indogangetic plains have problems adopting 100% but do adopt partial CA, especially NT in the wheat or other upland crop. So the paper looks at the impact of partial CA after 9 years. The treatments were tillage (main plot), crop residue management (sub-plot), and crop rotations (sub-sub-plot), respectively with permanent tillage or tillage only on rice, without or with all crop residues rice-legume combinations. Results show that post rice NT + residues in rice-chickpea-mung and rice-wheat-mungbean systems significantly increased SOC and carbon index from 0-15cm depth compared to the conventional practice after 9 years. Crop residue addition also increased SOC and C index compared to residue removal. Mean rice grain yield and sustainable yield index of the different systems after nine years were positively correlated with SOC storage.

This paper looks at the multitrophic network and its regulation of soil microbial carbon use efficiency (CUE) and SOC under different, long-term (15-year) tillage treatments. Conservation tillage (CT) enhanced microbial CUE, turnover, and SOC compared to traditional tillage (CK). Their results showed that the top-down control of protists in the soil micro-food web play an important role in improving microbial CUE under CT. By promoting the application of protists in targeted microbial engineering would contribute to the promotion of conservation agriculture and the improvement of soil C sequestration potential.

This is an interesting paper that compares the soil microbial biomass (SMB) and enzyme activity (EA) between no-till and integrated crop-livestock systems in tropical Brazil collecting soil samples from 0-20 cm depth. Their results show there are differences between agricultural systems but also sampling time and also interaction between these two items. More detailed results can be found in the paper. They conclude that there were significant seasonal responses to SMB and EA but more distinct responses to agricultural systems.

This paper hypothesizes that NT plus residue retention can improve energy productivity and efficiency while mitigating the carbon and water footprints, and GHG emissions in rice-wheat systems of Indo-Gangetic Plains of South Asia. Using two tillage practices, CT and NT with and without residue (R+, R-) they tested this hypothesis. The results are available in this paper. They conclude that NTR+ does support the hypothesis noted above and is a viable option to offset carbon emissions and water footprint, promotes carbon sequestration, enhances energy productivity and efficiency in the IGP of South Asia

Soil sodicity is expanding in arid and semi-arid areas of the world. This paper examines the reclamation potential of CA based management on this soil issue. They look at NT, use of legumes in rotation, residue mulch (R+), and sub-surface drip irrigation (SDI)  for 3 years in a rice-wheat system in India. The paper provides detailed results on productivity, economics, water and N use efficiency, soil pH, exchangeable sodium percentage, extractable anions, soil organic carbon, soil solution cations. They conclude that CA practices can reduce sodicity and improve soil chemical properties for a profitable crop production.

Since equipment suitable for no-till is vital for success, I included this paper from China that looks at the design of a furrow opener where residue is left on the soil. The paper proposes that this opener helps preserve soil moisture and that planted seeds are consistently covered with soil. The implement was tested in a soil bin and also using simulation. The paper provides results on what they they found for this furrow opener.

This paper conducted a meta-analysis on published research from India of CA effects on yield, SOC, soil health, and C-sequestration in different soils of the country. 544 paired observations comparing CA with CT from 35 Indian publications was used. There were differences in different locations and soil types listed in this paper. They conclude that promotion of CA in India will have to be location specific because of differences in crops, soil properties and climate.

Since cover crops (CC) are gaining acceptance in USA farming together with CA, I decided to add two articles that review the benefits of CC on soil properties. This review article looks at grasses, and broad leaf legume and non-legume as cover crops. It covers single and mixed cover crops and later their impact on soil health. may reduce soil bulk density, improve soil structure and hydraulic properties to facilitate increased water infiltration and storage. They review some of the benefits of crop residue additions such as enhancing soil organic C and N accretion, increase availability of P, K, Ca, Fe and Mg in some soil types under certain climatic conditions, provide a better condition for microbial activity, abundance, and diversity and through proper management provide an essential component of soil conservation practices for enhanced soil health.

This study looks at the willingness of Canadian farmers in Quebec to accept compensation (WTA) fr adopting a direct seeding, mulch based cropping system (another name for CA?) (DMC). Their results show that their famers would demand 161 C$/ha to convert to DMC although they are only willing to convert 25% of their farm to DMC. I wonder if compensation payments to encourage farmers to adopt DMC is a good idea, but the paper discusses to reasons for reluctance or choice to do so. They end that more research is needed.

I was impressed by this video produced by CIRAD about the agriculture in the Carmague region of Southern France. It uses sub-titles in English since the dialogue is in French. It is a documentary about developing agricultural systems more resilient to climate change based on CIRAD experience with CA in rice and rice systems in France. They want to improve biodiversity and biomass production of crops through double cropping systems that include various crops including forage, cover crops and even market crops like melons and tomato.

Sentinel sites that had promoted CA for a long time were used in this paper. The paper attempted to understand what led to the success of CA adoption. They surveyed 620 farmers in Malawi divided into two groups ; those who had contact with host farmers and a control group. Almost a third of the farmers in both groups adopted full CA over a 2-year period, but 57% of the farmers in the treatment area adopted full CA but on 7% in the control group. However, fewer farmers adopted CA for a longer period even in the treatment areas with some dis-adoption. The key adoption factors in the sentinel sites include the availability of training, dedicated longer-term extension support coupled with farmer experiential learning through demonstration plots managed by host farmers. This peer to peer learning over time is critical for sustained adoption.

This article looks at the factors that influence the adoption of conservation tillage in South Dakota. They surveyed 486 commodity crop farming operations. A modified application of the theory of planned behavior (TPB) including controls for socioeconomic and demographic indicators is used to understand farmers’ current usage of CT. Results show that three constructs of the TPB—attitude, subjective norms, and perceived behavioral control—are positively and significantly correlated with the adoption of CT. Binary logistic regression models also show that attitude and perceived behavioral control are related to farmers’ likelihood of adopting CT. Farm size and farmers’ level of education were also positively associated with CT adoption.

One key issue for CA is development of appropriate machinery for farmers. This article from China looks at the design and testing of a row cleaner for straw. The traditional NT seeder in China has a low straw cleaning rate and high working resistance. This paper addresses this problem with something they call a bionic elastic row cleaner. It has curved teeth and a torsion spring for throwing straw. Results show that it improved the cleaning rate and and the working resistance and is suitable for maize straw mulching.

This paper reports on a field study to assess the productivity, soil health and carbon dynamics of a soybean-wheat system under 4 tillage and residue management treatments (TRMPs); 1) CT w/o residue, 2) CT + residue in both crops, 3) NT w/o residue, and 4) NT + R in both crops. Also 5 organic-nutrient practices (ONMPs). Among the TRMPs, NT +R improved system productivity compared to CT - R. They conclude that the soybean-wheat NT + R at 6 t ha−1 year−1 + NF-based ONMPs (N5) harness higher and sustained productivity under this cropping system while improving soil-health and soil carbon-pools in sandy-loam soils of the north-Indian plains and similar soils across south-Asia.