Carbon Mineralization Rates and Kinetics of Surface-Applied and Incorporated Rice and Maize Residues in Entisol and Inceptisol Soil Types

Mineralization of carbon (C) is a burning issue that is regulated by soil attributes. It has direct impacts on crop productivity and quantification of organic residues addition in soil. For better understanding and achievement of potential tillage benefits, a comprehensive scientific understanding of C mineralization is very important. Therefore, a laboratory incubation experiment was conducted to investigate the C mineralization rates and kinetics of crop residues (rice and maize) when applied on the surface (as zero-tillage, ZT) and incorporation (as conventional tillage, CT) in four different soil types (S1 and S2 of Entisol; S3 and S4 of Inceptisols) of West Bengal state, India. Results showed that after 7 days of incubation, there was a rapid phase of decrease in CO2-C. It continued up to day 14 followed by a sluggish nature of CO2 emission up to day-42, and after that almost levelling off in all subsequent periods up to the end of 126 days of incubation. It was evident from the kinetic models that C mineralization from the residues followed the exponential model: C = C0 (1 − e−kt). Similar rate constant (k) values were recorded in both placement methods, but the rate of maximum potential mineralizable (C0k) residue C was higher under residue incorporation treatments for both rice and maize residue. However, the rice and maize residues showed almost similar amounts of C mineralized over time when applied on the surface. The future prediction analysis using the equation C = C0 × e−kt suggested that the residues incorporated into the soil release a maximum C irrespective of residue type. We conclude that the residues when incorporated into the soil significantly increase the C footprints through maximum C mineralization; leaving the crop residues on the soil surface reduces the C footprints which helps in achieving sustainability from an environmental perspective.

Characterisation of Bt maize IE09S034 in decomposition and response of soil bacterial communities

Returning straw to the soil is an effective way to improve the soil quality. As genetically modified (GM) crops experience expanded growing scales, returning straw to the soil could also be necessary. However, the impact of GM crop straws on soil safety remains unclear. The environment (including soil types, humidity and temperature) can result in a significant difference in the diversity of soil bacterial communities. Here, we compared the impacts of the straw from Bt maize IE09S034 (IE) and near-isogenic non-Bt maize Zong31 (CK) on soil bacterial community and microbial metabolic activity in three different environments. Sampling was carried out following 6–10 months of decomposition (May, June, July, and August) in three localities in Chinese cities (Changchun, Jinan, and Beijing). Our results showed that Bt maize residues posed no direct impact on soil bacterial communities in contrast to the environment and decomposed time. The microbial functional diversity and metabolic activity showed no significant difference between IE and CK. The results could be a reference for further assessing the effect of Bt maize residues on the soil that promotes the commercialisation of Bt maize IE09S034.

Lumbricus terrestris regulating the ecosystem service/disservice balance in maize (Zea mays) cultivation

Background and aim Plant pathogenic and mycotoxin-producing Fusarium species are globally widespread and lead to large annual yield losses in maize production (ecosystem disservice). Systems with reduced tillage and mulching are particularly under threat. In the present study, the bioregulatory performance (ecosystem service) of the common earthworm species Lumbricus terrestris was analysed regarding the suppression of three economically relevant Fusarium species, and the reduction of their mycotoxins in the maize mulch layer, taking into account the size of maize residues. Methods A mesocosm field experiment was conducted in a reduced tillage long-term field trial on loam soil. Artificially Fusarium-infected maize residues of two size classes were used as a mulch layer. Impacts of the earthworm species on DNA amounts of Fusarium graminearum, F. culmorum, and F. verticillioides and concentrations of the mycotoxins deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-AcDON), and zearalenone (ZEN) were analysed. Results The results reflect that Fusarium regulation by L. terrestris was species-specific and covered the whole spectrum from suppression (F. graminearum) to slight promotion (F. verticillioides). Regarding the mycotoxins, a significant acceleration of the degradation of all three toxins was detected. Fine chopping of the chaff (< 2 cm) did not significantly alter the earthworms’ regulatory capacity. Conclusion While L. terrestris can shift the ecosystem service/disservice balance in both directions with respect to Fusarium regulation, it shifts it towards ecosystem services with respect to mycotoxin degradation. In synergy with adapted agricultural management, this natural bottom-up effect can help to keep soils healthy for sustainable production in the long run.

Soil fauna regulates the ecosystem service/disservice balance in mulched soils

&lt;p&gt;A sustainable agricultural management can contribute to promoting soil biodiversity performance, thereby preserving soil functions and ensuring the provision of soil biota-induced ecosystem services. In order to make the best possible use of these services for the benefit of agricultural production, a better understanding of interlinkages between management measures, ecosystem service/disservice balance and soil self-regulation potential is essential. In this context, it is well known that the reduction of soil tillage intensity combined with mulching techniques, on the one hand, promote the survival, development and spread of plant pathogenic mycotoxin-producing soil-borne fungi, but, on the other hand, enhance the diversity of antagonistic mycotoxin-degrading fungivorous soil animals. However, up to now it is still unclear, which ecosystem service/disservice balance results from both pathways and which self-regulation mechanisms are involved.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;To analyse and assess the bioregulation potential of fungivorous soil faunal key species (earthworms: Lumbricus terrestris, collembolans: Proisotoma minuta, enchytraeids: Enchytraeus crypticus and E. christenseni) on economically relevant plant pathogenic species of the fungal genus Fusarium (F. graminearum, F. culmorum, F. verticillioides) and its mycotoxins (deoxynivalenol (DON), zearalenon (ZEN), 3-acetyl-deoxynivalenol (3AcDON) and fumonisin B1 (FB1)) in maize residues, field and laboratory experiments were performed as part of the EU BiodivERsA project SoilMan. Based on these studies the following hypotheses were tested: (1) soil faunal key organisms supress Fusarium species and reduce their mycotoxins in maize residues, (2) the bioregulation potential depends on substrate size and soil texture (3) interactions between fungivorous key species affect their bioregulation potential, (4) leaching of mycotoxins represents a potential risk for arable soils.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;The results reflect that soil faunal key species regulate amounts of F. graminearum and F. culmorum in maize residues depending on substrate size and soil texture, but did not affect amounts of F. verticillioides. Fungivorous soil animals significantly accelerate degradation rates of Fusarium mycotoxins by up to 300%, depending on soil faunal species, respective mycotoxin and soil texture. In particular, primary decomposers within the earthworm community (L. terrestris) are pivotal for the bioregulation of Fusarium species and their mycotoxins in the mulch layer. The bioregulation potential of the mesofauna (collembolans and enchytraeids) strongly depends on soil faunal interactions. The findings further indicate that the mycotoxins DON and ZEN leach from infected maize residues.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;The present studies contribute to improve understanding of the complex interrelations between arable management and ecosystem service/disservice balance in agroecosystems.&lt;/p&gt;