Conservation Agriculture Treatments Research Articles

Soil Carbon and Biochemical Indicators of Soil Quality as Affected by Different Conservation Agricultural and Weed Management Options

Burning of agricultural residues, cultivation of single crop varieties such as rice (Oryza sativa L.) and wheat (Triticum aestivum L.), and traditional soil tillage practices collectively contribute to the degradation of environmental quality, water systems, and soil resources. To address these issues, conservation agriculture (CA)-based crop management practice has emerged as one of the viable options. The current study was conducted with the aim to evaluate the effect of CA and weed management (WM) practices on carbon dynamics and biochemical properties of soil. The experiment included two factors, viz., CA and WM practices. The CA levels vary from conventional agriculture to partial CA (pCA1, pCA2, and pCA3) and full CA, while WM had three levels consisting of chemical control, integrated weed management, and weedy check. The results demonstrated that soil organic carbon (SOC) under the full CA treatment, was 30.6, 23.5, and 20.6 percent higher than conventional agriculture (T1), partial CA1, and partial CA2 practices, respectively. Similarly, labile fractions of carbon, KMnO4-C MBC, WSOC, and POC, in full CA increased by 46.3, 52.3, 152.4, and 15.6 percent, respectively, over conventional agriculture. Nonetheless, the total organic carbon exhibited no significant impact. The highest SOC stock was sequestered under full CA treatment, which was higher by 26.5 to 40.6 per cent than the rest of the CA treatments. Among biological properties, full CA resulted in 104.3 and 40.6 percent higher dehydrogenase and alkaline phosphatase activity than conventional agriculture. The impact of weed management practices was significant for KMnO4-C, with very labile carbon and alkaline phosphatase activity only in the surface soil layer. Soil quality index (SQI) followed the decreasing order as full CA (0.94) > partial CA3 (0.88) > partial CA2 (0.78) partial CA1 (0.77) > conventional agriculture (0.67) under different CA treatments, whereas WM followed herbicide (0.82) > weedy check (0.81) > IWM (0.80). The current study offered incredible information on soil carbon and biological indicators to monitor soil quality changes in rice–wheat cropping systems in response to conservation agriculture practices.

Long-Term Conservation Agriculture Influences Weed Diversity, Water Productivity, Grain Yield, and Energy Budgeting of Wheat in North-Western Indo-Gangetic Plains

Wheat is grown in an area totalling 31.1 million hectares in India. The North-western Indo-Gangetic Plains (IGP) constitutes the major share of area and production of wheat in India and is known as the wheat belt of India. However, sustaining wheat production under declining/lower resource-use efficiency in the existing rice–wheat cropping system has led to considerations about diversifying this system with a pigeon pea–wheat system (PWS) in the IGP of India. However, little or no information is available on the impact of CA-based PWS on weed dynamics, productivity, profitability, and resource-use efficiencies. Therefore, we studied these aspects in wheat under a long-term (~12 years) conservation agriculture (CA)-based PWS. Treatments were conventional till flatbed (CT), ZT permanent narrow beds (PNBR & PNB), broad beds (PBBR & PBB), and flat beds (PFBR & PFB) with and without residue (R) retention and different N levels (75% and 100% of the recommended N). The results showed that the Shannon–Weiner index and the Simpson dominance index were higher under the CA system in 2021–2022 than in 2010–2011 and 2015–2016, indicating a change in weed diversity over the period. Furthermore, the Sorensen similarity index showed that there was not much difference in weed diversity for 2010–2011. However, in 2015–2016 and 2021–2022 respectively, only 89% (0.89) and 62% (0.62) of weed species were common to both CT and CA systems, indicating a shift in weed species in the long-term CA system in 2021–2022. Residue retention and N dose decreased weed density at 30 days after sowing (DAS). All the CA-based (PFBR100N, PBBR100N, PNBR100N, PFBR75N, PBBR75N, and PNBR75N) treatments reduced the weed density and dry weight compared to CT at 30 DAS. Wheat grain yield and net returns increased by 11.6–14.9% and 19.4–23.8% over CT in CA treatments, of which PFBR100N and PBBR100N were superior. The PBBR100N and PBBR75N systems had water productivity significantly higher than CT. Residue retention in ZT permanent beds reduced energy productivity in CA than CT and no residue treatments. In the 12th year, CA with 75% N (PFBR75N, PBBR75N, PNBR75N) resulted in a higher partial factor productivity of N and total NPK applied. Contrast analysis showed that 75% N was comparable with 100% N on crop, water, and energy productivities and 75% N was superior to 100% N on partial factor productivity of N and total NPK. Thus, the permanent broad bed with residue and 100% N in the initial years and 75% N in later years can be adopted in the north-western IGP for better weed suppression, higher yield, profitability, and resource-use efficiency.

Intensification of Rice-Fallow Agroecosystem of South Asia with Oilseeds and Pulses: Impacts on System Productivity, Soil Carbon Dynamics and Energetics

Rice-fallow systems in South Asian countries play a pivotal role in increasing agricultural production. However, the productivity of these system is largely challenged by deteriorating soil health and limited residual soil moistures in dry-periods, precluding the possibility of winter and/or spring season crops after rice harvest. This investigation explores the possibilities of including winter and/or spring crops through conservation agriculture (CA)-based management practices and evaluates its effect on soil carbon dynamic, system productivity, energy and carbon budgeting. Field experiments were conducted at a farmer’s field in participatory modes at Chene Village, Jharkhand, India, and had five treatments comprising (1) fallow-land [FL]; (2) transplanted puddle rice (TPR)-fallow (winter)-fallow (summer), a typical cultivation practice of this region [RF]; (3) TPR–conventional-till mustard–conventional-till blackgram [CP]; (4) CA with zero-till transplanted rice (ZTTR)-ZT mustard–ZT blackgram [CA1]; (5) CA with zero-till direct seeded rice (ZTDSR)-ZT mustard–ZT blackgram [CA2]. Results revealed that CA2 comprising full CA practice of growing direct seeded rice, mustard and blackgram under ZT increased total soil organic carbon (TSOC) of 0–0.6 m soil layer by 14.3% and 10.3% over RF and CP, respectively. The C-sequestration rate was higher in CA treatments and varied from 0.55 to 0.64 Mg C ha−1 year−1. The system rice equivalent yield in CA2 during the initial four years was lower than CP but it was 23.7% higher over CP in fifth year. The CA-based system (CA2) enhanced the water productivity of rice, mustard and blackgram by 7.0%, 23.6% and 14.1% over CP, respectively. The CA2 treatment, having higher system productivity, better C-sequestration potential, lower C-footprint, higher energy and water productivity has very good potential for sustaining soil health and crop yield of rice-fallow systems.

Farmer participatory assessment of soil health from Conservation Agriculture adoption in three regions of East Africa

The challenges of soil degradation and low crop yield are being addressed in East Africa using a number of soil health-promoting farming systems including Conservation Agriculture (CA). CA is based on principles of minimal soil disturbance, continuous soil cover, and crop diversity, though implementation on farms may vary due to local circumstances. This study evaluated the effect of CA, as practiced by farmers, and compared farmer descriptions of soil health with scientific measures. CA and non-CA fields were compared in regions of Ethiopia (23 farms), Kenya (23 farms), and Tanzania (13 farms) with most fields repeatedly sampled for 2 to 3 years. CA and non-CA fields were located within meters, on soils with the same texture, growing similar crops. CA systems used precision planting, mostly with basins. Soil parameters were assessed using a participatory approach where farmers and field technicians collected data. CA practices improved qualitative soil characteristics as sensed by farmers (e.g., hoe-ability, crusting, smell, water infiltration), and this positive response was consistent across most fields. For qualitative data, the logarithm of the odds ratio estimates method was used to test the probability that CA would provide soil improvement. Fields under the CA treatment had a higher probability of rating better than non-CA fields. Quantitative measurements of pH and microbial respiration validated farmer assessments. CA-managed soils were weakly associated with darker colour, indicating higher soil organic matter. Sandy soils did not appear to improve with CA as dramatically as clay and loam soils, suggesting different CA strategies may be required. We discuss both benefits and drawbacks of this type of participatory, on-farm research. We conclude that farmer participation as citizen scientists will advance soil restoration in East Africa and increase the potential for farmer-to-farmer knowledge exchange of soil-improving practices.

Conservation Agriculture in Semi-Arid Zimbabwe: A Promising Practice to Improve Finger Millet (Eleusine coracana Gaertn.) Productivity and Soil Water Availability in the Short Term

Increasing within-season dry spells in Southern Africa in recent years have generated growing interest in conservation agriculture (CA) to secure crop yields, especially under rainfed systems. This study aimed to evaluate the effects of CA on finger millet’s (Eleusine coracana (L.) Gaertn) growth, yield and water use efficiency on nutrient-depleted sandy soils. Five treatments, namely (conventional tillage (control), conventional tillage + mulch (partial CA1), reduced tillage only (partial CA2), reduced tillage + mulching (partial CA3) and reduced tillage + mulching + intercropping (full CA)) were evaluated over two consecutive cropping seasons (2015/16 and 2016/17) on-farm in the village of Chidora in Hwedza District, southeast Zimbabwe. All mulched treatments had 15–32% more soil water content over the two growing seasons compared to the control. The higher soil water content under the mulched treatments significantly improved finger millet growth and development during both seasons as evidenced by the lower number of days to emergence (3 days less), greater shoot biomass, higher number of productive tillers and higher number of fingers produced. The full CA treatment achieved the best finger millet grain yield of 1.07 and 1.29 t ha−1 during the 2015/16 and 2016/17 seasons, respectively. Full CA, partial CA3 and partial CA1 increased finger millet grain yield by 70%, 14% and 17% during the 2015/16 cropping season compared to the control. During the 2016/17 cropping season, a similar trend in finger millet grain yield was observed. Full CA was also among the most efficient methods in terms of water utilization (WUE), especially during the 2015/16 season. We concluded that CA, particularly when practiced in full, was more effective at offsetting the water limitations imposed by intra-seasonal dry spells on finger millet and significantly improved productivity.

Conservation Agriculture Affects Grain and Nutrient Yields of Maize (Zea Mays L.) and Can Impact Food and Nutrition Security in Sub-Saharan Africa.

Maize is a major staple and plays an essential role in food and nutrition security in Sub-Saharan Africa (SSA). Conservation agriculture (CA), a climate-smart agriculture practise based on minimum soil disturbance, crop residue retention, and crop diversification, has been widely advocated but without extensive research on the impact it may have on maize nutrient composition, and food and nutrition security. This study assessed the grain yield, macro- and micronutrient mineral content, and nutrient yield of eight maize varieties grown in Malawi, and how these are affected by CA practises over two seasons. The minerals were analysed by inductively coupled plasma (ICP) coupled to optical emission spectroscopy (OES) and to mass spectroscopy (MS). Grain yield and Se content differed among the varieties, while C, N, Fe, K, Mg, Mn, P, and Zn were similar. The local variety Kanjerenjere showed lowest grain and nutrient yields. The open-pollinated varieties (OPVs) concentrated more minerals than the F1 hybrids, but the latter showed higher yields for both grain and nutrients. Typical consumption of the eight maize varieties could fully meet the protein and Mg dietary reference intake (DRIs) of Malawian children (1–3 years), as well as Mg and Mn needs of adult women (19–50 years), but their contribution to dietary requirements was low for Fe (39–41%) and K (13–21%). The trials showed that CA increased grain yield (1.2- to 1.8-fold) and Se content (1.1- to 1.7-fold), but that it had no effect on C, K, Mg, P, and Zn, and that N (1.1- to 1.2-fold), Mn (1.1- to 1.8-fold), and Fe (1.3- to 3.4-fold) were reduced. The high increase in grain yield under CA treatments resulted in increased yields of protein and Se, no effect on the yields of K, Mg, Mn, P, Zn, and reduced Fe yield. Conservation agriculture could contribute in reducing the risk of Se deficiency in Malawian women and children but exacerbates the risk of Fe deficiency. A combination of strategies will be needed to mitigate some of the foreseen effects of climate change on agriculture, and food and nutrition security, and improve nutrient intake.

On-Station and On-Farm Assessment of the Effects of Soil Cover on Conservation Agriculture Performances in Western Burkina Faso

Conservation agriculture (CA) is one option for dealing with such a challenge, but its main difficulty in West Africa is in maintaining permanent soil cover, particularly with crop residues, due to their preferential use for livestock fodder. The aim of our study was to determine the effect of crop residue mulching on the efficiency of cropping systems based on the principles of conservation agriculture. The experimental design was based on on-station experiments, intended to assess the specific effect of different levels of crop residue mulching on the biological and chemical soil fertility parameters, while in on-farm experiments we mainly assessed the ability of farmers to actually collect crop residues for soil cover and the associated effects on weeds and yields. The on-station experimental design was in fully randomized factorial blocks comprising five treatments and three replicates. The treatments compared the conventional system, tillage and cropping without mulching, and CA systems with 1 ton, 2 tons, and 4 tons of straw per hectare in plots of 10 m2. The effects of CA on the macrofauna, respiratory activity, and soil chemical parameters were evaluated in the 2014 and 2015 growing seasons. For the on-farm experiments, the conventional and CA practices of 15 farmers were compared to conventional practices in 2013 and 2014 in plots of 626 m2. The on-station results showed that the presence of crop residue mulching induced an increase in the density of termites. A significant release of carbon dioxide (CO2) in the CA treatments compared to the conventional treatment was also observed. For the chemical parameters (pH, N, P and K) were significantly and positively affected by mulch in the top 5 centimeters of soil. The on-farm experiments confirmed the difficulty of farmers in collecting enough biomass, with negative effects on grass cover leading to generally lower yields than conventional treatments. Other practices also affected the results, such as the maize sowing date, the gap between sowing and weeding, the gap between sowing and urea supply, the number of years of CA practices in the plot and, the gap between maize sowing and cowpea sowing. For the farmers having the human resources to collect enough crop residues for soil cover and follow the steps of the crop management sequences, it was possible to maintain yields compared to the conventional practice.

Eukaryotes in soil aggregates across conservation managements: Major roles of protists, fungi and taxa linkages in soil structuring and C stock

The stabilization of soil organic carbon (SOC) promoted by conservation agriculture (CA) depends on soil aggregation. Aggregation protects SOC and creates heterogeneous microhabitats hosting diverse soil biota which in turn promote aggregation. A long-term experiment, studying the interaction of tillage with nitrogen (N) fertilization on a soybean-wheat rotation, was used to investigate eukaryotic community diversity, composition, and structure within small macroaggregates (sM) and occluded microaggregates (mM). Using high-throughput Illumina sequencing, we found (i) a different eukaryote diversity response to management intensification across soil aggregates and soil depths; (ii) a conserved core community composition of eukaryotes across CA treatments and aggregates at surface and subsurface layers; (iii) a different effect of tillage on eukaryotic community structure in sM and mM along the soil profile according to N availability; (iv) a positive association of protists, and fungi with the amount of sM and mM, and their SOC content; (v) a stronger complexity of within- and cross-domain networks (eukaryotes and eukaryotes-prokaryotes) in mM than in sM at surface layer. Overall, our findings demonstrate for the first time that protists together with fungi play major roles in soil structuring and C cycling, and that Cercozoa represent hubs in soil biota aggregate networks.

Comparative short-term performance of soil water management options for increased productivity of maize-cowpea intercropping in semi-arid Zimbabwe

Rainfall variability poses a great challenge to rainfed cropping in sub-Saharan Africa. We evaluated, over three cropping seasons, conservation agriculture (reduced tillage and mulching) and farmer prioritized conventional tillage- and mulching-based options on seasonal soil water retention, and subsequent productivity of maize ( Zea mays L.) and cowpea ( Vigna unguiculata Walp L.) in mono- and inter-crops in Eastern Zimbabwe. The experiments were established on sand and clay soils. The first cropping season (2014/15) received evenly distributed rainfall (hereinafter referred to as ‘wetter’), while the two succeeding seasons (2015/16 and 2016/17) had high incidences of intra-seasonal dry spells (hereinafter referred to as ‘drier’). Overall, conventional tillage had 10–31% and 27–40% more moisture than conservation agriculture treatments on sand and clay soils, respectively. Soil moisture was most retained in intercrop under mulch-based conventional tillage. Maize grain yield during the ‘wetter’ season on sand soil was highest and least ( P > 0.05) in intercrop under conservation agriculture (2.3 Mg ha −1 ) and mulch-based conventional tillage (1 Mg ha −1 ), respectively. On clay soil, intercrop under mulch-based conventional tillage (2.4 Mg ha −1 ) yielded the best. During the ‘drier’ seasons, intercrop under mulch-based conventional tillage achieved the best maize grain yield on both sand (1.5 Mg ha −1 ) and clay (1.4 Mg ha −1 ) soils. Mulching increased maize grain yield by 55–90% during the ‘drier’ seasons, but reduced water use efficiency (WUE) by approximately 15% during the ‘wetter’ season. Over the three seasons, cowpea grain yield did not exceed 1 Mg ha −1 in both mono- and inter-crops. The study revealed contrasting short-term effects of soil water management options on soil moisture retention and intercropping productivity as dictated by seasonal rainfall variability and soil type. These findings point to the need for tillage and mulching typologies across soil types to minimize negative effects of rainfall variability on crop productivity. • Mulch-based conventional tillage retained more soil water than CA in the short term. • Mulching increased productivity of maize-cowpea intercrop. • Mulch-based conventional tillage reduced maize productivity under high rainfall on sandy soil. • CA increased maize yield under high rainfall on sandy soil.

Water budgeting in conservation agriculture-based sub-surface drip irrigation in tropical maize using HYDRUS-2D in South Asia

In water scarce regions of South Asia, diversification of rice with maize is being advocated towards sustainability of cereal-based cropping systems. Adoption of innovative agronomic management practices, i.e., conservation agriculture (CA) and sub-surface drip irrigation (SSDI) are considered as key strategies for much needed interventions to address the challenges of water scarcity under projected climate change. Benefits from CA and SSDI concerning water economy are well-established, however, information about their complementarity and water budgeting in cereal-based systems are lacking. A field study was conducted with process-based model (HYDRUS-2D) to understand water transport, root water uptake and components of soil water balance in maize grown in rotation with wheat after five years of continuous adoption of conservation agriculture. In this study, altogether eight treatments comprising of 6 CA+ treatments (CA coupled with SSDI); permanent beds using sub-surface drip (PB-SSD) with (WR) and without (WOR) crop residue at different N rates, 0, 120 and 150 kg N ha−1 were compared with CA (PB using furrow irrigation-FI with crop residue-120 kg N ha−1) and conventional tillage practices (CT) (CT using FI without crop residue-120 kg N ha−1). Results showed that the model could simulate the daily changes in profile soil water content with reasonable accuracy in all the treatments. Simulated soil water balance indicated higher cumulative root water uptake (CRWU), lower cumulative evaporation (CE) and higher soil water retention in CA+ (PB-SSD+ crop residue at 150 and 120 kg N ha−1) than CA and CT plots. Hydrus-2D model efficiency > 0, RMSE between 0.009–0.026 and R2 value between 0.80–0.92 at P < 0.01 indicates that the model is performing efficiently. The mean evaporation from CA+ treatments was 10 and 36% less than CA and CT treatments, respectively. On average, CRWU under CA+ treatments were 14–48% higher than FI treatments. The mean cumulative deep drainage in CA+ plots was 80–100 mm less than CA and CT plots. In CA+ based plots significantly higher biomass production and radiation use efficiency were observed with reduced water use than CA and CT. Therefore, the study justifies the water-saving nature of CA+, while maintaining higher productivity and meeting the transpiration demand of crops and halting unnecessary evaporation and deep drainage losses.

Productivity, profitability and input-use efficiency of direct-seeded rice (Oryza sativa) under conservation agriculture

A field experiment was conducted during kharif 2016-17 at ICAR-Indian Agricultural Research Institute, New Delhi to assess the long term impact of conservation agriculture (CA) on productivity, profitability and input-use efficiency of rice (Oryza sativa L.) under a rice-wheat cropping system (RWCS). Pooled results revealed that rice grain yield under the CA-based zero till direct seeded rice (ZTDSR) + mungbean residue (MR) – zero till wheat (ZTW) + rice residue (RR) – zero tilled summer mungbean (ZTM) + wheat residue (WR) both with 100% N (4.9 t/ha) and 75% N (4.8 t/ha) was statistically comparable to the conventional practice, i.e. transplanted puddled rice (TPR) – conventional till wheat (CTW) (5.2 t/ha) and TPR – ZTW (5.4 t/ha). Although rice grain yield under ZTDSR+MR–ZTW+RR– ZTM+WR [100% N] was ~5.7% lower compared to farmers’ practice TPR–CTW, net returns of rice (₹ 41.1×103 / ha) was 119.5% higher compared to TPR-CTW, chiefly due to the lower cost of cultivation of ZT-DSR (₹ 47.5×103 / ha) as compared to CT-TPR (₹ 74.8×103 /ha). Partial factor productivity of NPK was highest under the CA treatment ZTDSR+MR–ZTW+RR–ZTM+WR [75% N] (32 kg grain/kg NPK) while ZTDSR+MR–ZTW+RR–ZTM+WR [75% N] [100% N] observed the highest irrigation water use efficiency (0.57 kg/m3). Thus, the novel CA practice ZTDSR+MR–ZTW+RR–ZTM+WR can provide comparable rice yields with higher net returns and nutrient (75% N) and irrigation use efficiencies compared to conventional farmers practice TPR–CTW and hence its adoption may be recommended.

The Response of Water and Nutrient Dynamics and of Crop Yield to Conservation Agriculture in the Ethiopian Highlands

Smallholder agriculture constitutes the main source of livelihood for the Ethiopian rural community. However, soil degradation and uneven distribution of rainfall have threatened agriculture at present. This study is aimed at investigating the impacts of conservation agriculture on irrigation water use, nutrient availability in the root zone, and crop yield under supplementary irrigation. In this study, conservation agriculture (CA), which includes minimum soil disturbance, grass mulch cover, and crop rotation, was practiced and compared with conventional tillage (CT). We used two years’ (2018 and 2019) experimental data under paired-t design in the production of a local variety green pepper (Capsicum annuum L.). The results showed that CA practices significantly (α = 0.05) reduced irrigation water use (13% to 29%) and runoff (29% to 51%) while it increased percolated water in the root zone (27% to 50%) when compared with CT practices under the supplementary irrigation phase. In addition, CA significantly decreased NO3-N in the leachate (14% to 44%) and in the runoff (about 100%), while PO4-P significantly decreased in the leachate (33% to 50%) and in the runoff (16%) when compared with CT. Similarly, CA decreased the NO3-N load in the leachate and in the runoff, while the PO4-P load increased in the leachate but decreased in the runoff. The yield return that was achieved under CA treatment was 30% higher in 2018 and 10% higher in 2019 when compared with the CT. This research improves our understanding of water and nutrient dynamics in green pepper grown under CA and CT. Use of CA provides opportunities to optimize water use by decreasing irrigation water requirements and optimize nutrient use by decreasing nutrient losses through the runoff and leaching.

Similar specific mineralization rates of organic carbon and nitrogen in incubated soils under contrasted arable cropping systems

No tillage is often thought to mitigate greenhouse gas emissions from agricultural land by increasing soil carbon storage, because of a reduced mineralization of soil organic carbon (SOC) and nitrogen (SON). Regrettably, most available references on this topic come from laboratory incubations of disrupted soil from superficial soil layer. Here, we compare SOC and SON mineralization rates in the long-term experiment of La Cage (France) under conventional (CON), low input (LI), conservation agriculture (CA) or organic (ORG) management. Disturbed soil samples from the 0−27 cm soil layer of all treatments were laboratory incubated for four months, while undisturbed CON and CA soil cores were incubated to account for tillage effects. Physical disturbance decreased SOC and SON mineralization. Model fitting showed that the size of the C labile pool and the C and N mineralization rates of the slow pool were 1.5–2.3-fold greater in undisturbed soil cores than in disturbed ones, which may be due to a higher abundance of labile SOC (e.g. plant residues) in undisturbed soil cores. All cropping systems exhibited similar specific rate of mineralization, expressed per unit of SOC, SON or microbial biomass C, both for disturbed and undisturbed soils. Similar mineralization in CA and CON undisturbed soil cores may result from the balance between higher amount of labile OM and less favourable soil structure for decomposition in CA. Similar mineralization rates in disturbed soil cores suggest that OM decomposability and environmental conditions for decomposers were similar between cropping systems. Overall, these results confirmed the hypothesis previously made in silico to explain the differences in SOC storage in this experiment (Autret et al., 2016). Our results together with the increased SOC stocks observed in CA and ORG treatments suggest that increased biomass returns to soil or changes in microbial physiology may be the main drivers of SOC storage.

Forage and maize yields in mixed crop-livestock farming systems: Enhancing forage and maize yields in mixed crop-livestock systems under conservation agriculture in sub-humid Zimbabwe

In mixed crop-livestock farming systems, smallholder farmers face the challenge of insufficient dry season livestock feed whilst crop production is mainly constrained by poor soil fertility and erratic rains. Conservation agriculture (CA) which is premised on three main principles namely minimal soil disturbance, crop rotations and mulching is being promoted as a potential solution to declining soil productivity. However, farmers implementing CA in mixed crop-livestock systems are conflicted by the use of crop residues either as livestock feed or as mulch under crop production. A study was carried from 2012/13 to 2014/15 season in Murehwa, a sub-humid region of Zimbabwe, to evaluate the effects of maize-legume cropping systems on forage, maize grain yield and gross margins. In this context, forage refers to the plant material/biomass harvested for livestock feeding. The cropping systems involved one conventional tillage practice with continuous sole maize (CT), four CA treatments consisting of continuous sole maize, maize-mucuna intercrop, maize-cowpea intercrop and maize-groundnut/soybean rotations. The experiment was replicated on eight farmers’ fields with each farmer treated as a replicate. Maize-mucuna (4 134 kg ha-1) and maize-cowpea (3 999 kg ha-1) intercrop systems significantly increased forage yield compared to CA sole maize (3 646 kg ha-1) and CT sole maize (3 076 kg ha-1). Among the rotations, maize-soybean rotation system performed better than the maize-groundnut system with respect to forage yield and maize grain. Intercropping and sole cropping systems however showed no significant maize grain yield difference. The highest and lowest gross margins/ha were obtained from the maize-mucuna intercrop (US$1395) and maize-soybean rotation system (US$507), respectively. The study thus suggests that farmers can grow legumes as intercrops with maize without any loss in maize grain yield. Maize-mucuna intercropping was the best of the tested cropping systems with respect to forage yield and gross margins in mixed crop-livestock systems of Murehwa.

Multi-functional assessment of soil health under Conservation Agriculture in Cambodia

As a response to the worldwide challenge raised by soil degradation, Conservation Agriculture (CA) was proposed to help restoring the three main soil functions, i.e. carbon transformation, nutrient cycling and structure maintenance. However, there is still a lack of integrative studies that assess the overall impact of CA on soil health. To fill the gap, Biofunctool®, a set of in-field indicators, was developed to monitor changes in soil biological functioning. In this study, Biofunctool® was used to assess the impact of a conventional tillage (CT) and three CA annual-based cropping systems on soil health on a Cambodian Oxisol. Eight indicators related to the three soil functions were monitored and integrated into a Soil Quality index (SQI), i.e. the Biofunctool® Index. Overall, we found that soil health was twice higher under the CA treatments than under CT treatment. Although it was similar in the three CA treatments, the contribution of each soil function to the soil health diverged. An analysis of soil carbon dynamics also showed that CA support short-term soil organic carbon stabilization compared to CT. This study demonstrates that Biofunctool® is a robust, relevant, time-and cost-effective in-field assessment tool that can be used in multiple ways including cropping system management, capacity building of local stakeholders, and policy dialogue.

Tillage and crop rotations enhance populations of earthworms, termites, dung beetles and centipedes: evidence from a long-term trial in Zambia

AbstractMacro-organisms contribute significantly to soil fertility improvement. The influence of conservation agriculture (CA) in southern Africa on their populations has not yet been fully understood. Thus, the objective of the current study was to evaluate the effects of CA and conventional tillage on below ground biological activity in a CA long-term trial in Monze, Zambia from 2011 to 2013. The study had ten treatments which differed by tillage systems (conventional ploughing, planting basins and direct seeding) and crop diversification intensity (sole cropping, 2- or 3-year crop rotations) involving maize, cotton and sunn hemp. These factors were combined to create rotation-tillage (RotTill) treatments. Sampling of macrofauna was done once per year using a metal frame measuring 0.25 m2, hand-sorted to 30-cm depth. RotTill treatments had a significant effect on earthworms (Lumbricus terrestris), termites (Coptotermes formosanus), dung beetles (Scarabaeus viettei) and centipedes (Lithobius forficatus). Earthworms and termites were more abundant in CA treatments than in conventionally ploughed (CP) treatments. Biota diversity was generally higher in CA treatments than in CP controls. Conventional mouldboard ploughing generally reduced macrofauna, thus affecting biological soil fertility and the beneficial effect of the interactions of these organisms with the soil. CA treatments had the highest maize grain yields throughout the study period. Based on the results, reduced tillage systems and crop rotations increase biological activity shown by increased densities of termites and earthworms.

Short‐Term Impacts of Conservation Agriculture on Soil Physical Properties and Productivity in the Midhills of Nepal

Core Ideas Aggregation and time‐to‐pond were improved under conservation agriculture.Conventional practice had a higher sorptivity rate than conservation agriculture.Maize yields were similar for conservation agriculture and conventional practice in the first year of production.Maize yields were less in conservation agriculture than in conventional practice in the second year due to patchy plant stands in conservation agriculture.There were no differences in yield between conservation agriculture and conventional practice for rapeseed or wheat. Conservation agriculture (CA) is a management system characterized by zero or minimum tillage, permanent soil cover with crop residue or plant growth, and crop rotation. This study investigated the impact of conservation tillage, crop type, and planting date on crop productivity and the soil physical properties for 2 yr following conversion to CA. After 2 yr, average mean weight diameter of dry aggregates for the 0‐ to 5‐cm and 5‐ to 10‐cm soil depths were 45 and 24% greater in the CA treatment than the conventional practice (CP) treatment, respectively. However, soil sorptivity was about three times slower in CA than in CP for rapeseed (Brassica napus L. toria) rotation treatments, but only 62% slower in CA than CP for wheat (Triticum aestivum L.) rotation treatments. Soil bulk density to a depth of 15 cm was greater in CA (1.30 g cm−3) than CP (1.24 g cm−3), but only for late‐planted treatments. Maize (Zea mays L.) yields for CA were not different from CP in the first year, but were 1.4 Mg ha−1 for CA and 5.0 Mg ha−1 for CP in the second year due to poor stand establishment under CA. There were no effects of CA on dry‐season rapeseed and wheat. Results suggest that during the transition of CP to CA, soil physical properties can be improved but yields may remain constant or decline. Achieving equivalent yield outcomes between CA and CP will largely depend on equivalent stand establishment.

Soil hydraulic response to conservation agriculture under irrigated intensive cereal-based cropping systems in a semiarid climate

Assessment of soil hydraulic response to conservation agriculture (CA) practices may assist in better management decisions in agriculturally sensitive and environmentally fragile agroecosystems. Although, the potential of management induced temporal changes of soil hydraulic properties (SHPs) has been studied particularly in relation to tillage, few studies have evaluated combined effects of tillage, crop residue retention and cropping sequence, which are essential components of CA, on near-saturated SHPs under field conditions. The objective of this study was thus to evaluate the long-term effect after eight years of CA practices and short-term effect of crops on near-saturated soil hydraulic conductivity, k(h), and water transmission properties under irrigated intensive cereal-based cropping systems in a semiarid climate (NW Indo-Gangetic Plains, India). There were four treatments: (1) conventionally tilled rice-wheat cropping system, (2) reduced till CA-based rice-wheat-mungbean system, (3) no-till CA-based rice-wheat-mungbean system and (4) no-till CA-based maize-wheat-mungbean system. Steady state infiltration rates were obtained at four pressure heads by hood infiltrometer consecutively over two cropping seasons, i.e., during harvest season of rice/maize (October 2017) and maximum crop growth stage of wheat (February 2018). Data were analysed in terms of k(h), flow weighted mean pore radius (r0), hydraulically active porosity (ε) and threshold pore radius (rbp), a new pore measure indicative of macropore stability derived by substituting soil’s bubble pressure in the capillary equation. Our results showed that no till-based CA enhanced k(h) as compared with conventional cultivation practice. Although the interaction effect of treatments with crop seasons were statistically non-significant (p < 0.05), considerable changes of soil hydraulic properties were observed over crop seasons under CA treatments. Transition from maize to wheat in the crop sequence reduced k(h) values by about 55, 44, 34 and 40% at pressure heads of 0, −1, −2 and −4 cm, respectively. In contrast, transition from rice to wheat in rice-based no till CA increased k(h) values by 129, 164, 124 and 24% in the same pressure head ranges. Irrespective of crop seasons, higher k(h) was observed under CA due to formation of macropores with better continuity, greater size and numbers as compared with conventional intensive tillage treatment. Reduced till-based CA showed an intermediate effect with respect to the different soil hydraulic characteristics in both crop seasons. Moreover, higher r0 values were observed for a given k(h) for CA treatments suggesting that interaggregate pores are the dominant pathways of infiltration flux in CA. A relatively smaller temporal variation of rbp was indicative of a more stable macropore system established by rice-based CA as compared with maize-based CA. CA also enhanced hydraulically active macropores as compared with intensive tillage based conventional agriculture. Overall, the results revealed that the potential impacts of CA on near-saturated SHPs are largely governed by characteristic changes in macro- and interaggregate pores.

Crop rotation and residue management effects under no till on the soil quality of a Haplic Cambisol in Alice, Eastern Cape, South Africa

Improvement and maintenance of soil quality is critical in achieving environmental and agricultural sustainability. Conservation agriculture (CA) technologies are widely reported to improve soil quality of arable soils in the long term. The objective of this study was to investigate and quantify the effects of crop rotations and residue management under no till on the soil quality of a Haplic Cambisol in Alice, Eastern Cape, South Africa. The study made use of plots from a CA field trial laid out in a split-plot design. The main plots were crop rotations viz maize-fallow-maize (MFM), maize-fallow-soybean (MFS); maize-wheat-maize (MWM) and maize-wheat-soybean (MWS). The sub-plots were allocated to residue management viz residue removal (R−) and residue retention (R+). The Soil Management Assessment Framework (SMAF) was used to evaluate the changes in soil quality after three years of CA treatment application. Soil organic carbon (SOC), microbial biomass carbon (MBC), β‑glucosidase (BG) activity, extractable P and K, soil pH, electrical conductivity (EC), bulk density (ρb) and aggregate stability (AGS) were measured and used in the calculation of the SMAF soil quality index (SQI) which was used as an indicator of soil quality. Crop rotations significantly (p < 0.05) influenced mineral N, soil respiration (CO2-C) as well as micro-nutrients Zn, Mn and Cu. Crop residue retention significantly (p < 0.05) improved soil organic C, microbial biomass C, soil respiration (CO2-C), mineral N, extractable P and K, Ca, Mg, Zn, Fe, Cu, Mn, EC and AGS. The study revealed the significance of crop residue management effects on the SQI score, while crop rotation and the interaction of crop rotation and residue management had no significant effects. Our study findings indicated that the SMAF was an effective monitoring tool for assessing soil and crop management effects on the soil quality of the South African Haplic Cambisol and possibly other soils.

Evaluation of the performance of the EPIC model for yield and biomass simulation under conservation systems in Cambodia

Limited field studies have been performed to evaluate the impacts of conservation agriculture (CA) on crop yields and soil organic carbon sequestration in tropical conditions. In this study, we used the Environmental Policy Integrated Climate (EPIC) model to evaluate the impact of CA and conservation tillage (CT) on crop yields in tropical conditions for unique upland rice, soybean, and cassava cropping systems in Cambodia. New crop parameters were developed and tested for cassava, sesame, banana, sunn hemp, stylo, and congo grass. The results show that EPIC successfully replicated crop yields of soybean, upland rice, maize, and cassava based on R2 statistics ranging from 0.62 to 0.88 and percent bias (PBIAS) values ≤10%. However, it cannot be concluded that the model can accurately capture the biomass for all the individual crops due to limitations in the observed biomass data. The cassava and maize biomass were simulated satisfactorily, resulting in R2 values of 0.81 and 0.75, respectively. However, the computed PBIAS for the biomass estimates of the two crops were >25%. In contrast, the predicted rice and soybean biomass met PBIAS criteria (≤23%) but resulted in weak R2 statistics of ≤0.20, indicating inaccurate replications of the measured biomass. Similarly, the cover crop mean biomass and PBIAS statistics were acceptable but the R2 values were not. Overall, the model tended to overestimate the measured crop biomass. No significant difference was found in the simulated crop yields between the CA and CT treatments. However, the predicted rice and soybean results reflect an increased yield trend over time for the CA treatments, versus no discernible trend for the cassava and maize yields.