• Authors:
    • Horwath, W. R.
    • Wroble, J. F.
    • Munk, D. S.
    • Wallender, W. W.
    • Singh, P. N.
    • Mitchell, J. P.
    • Hogan, P.
    • Roy, R.
    • Hanson, B. R.
  • Source: California Agriculture
  • Volume: 66
  • Issue: 2
  • Year: 2012
  • Summary: Reducing tillage and maintaining crop residues on the soil surface could improve the water use efficiency of California crop production. In two field studies comparing no-tillage with standard tillage operations (following wheat silage harvest and before corn seeding), we estimated that 0.89 and 0.97 inches more water was retained in the no-tillage soil than in the tilled soil. In three field studies on residue coverage, we recorded that about 0.56, 0.58 and 0.42 inches more water was retained in residue-covered soil than in bare soil following 6 to 7 days of overhead sprinkler irrigation. Assuming a seasonal crop evapotranspiration demand of 30 inches, coupling no-tillage with practices preserving high residues could reduce summer soil evaporative losses by about 4 inches (13%). However, practical factors, including the need for different equipment and management approaches, will need to be considered before adopting these practices.
  • Authors:
    • Twomlow, S.
    • Mupangwa, W.
    • Walker, S.
  • Source: Field Crops Research
  • Volume: 132
  • Year: 2012
  • Summary: Proponents of conservation agriculture (CA) argue that the CA approach offers the greatest opportunity to increase the productivity in smallholder agro-ecosystems. This study was designed to assess (1) first year maize, cowpea and sorghum yield responses to a combination of reduced tillage and mulching and (2) maize yield responses to rotation with cowpea and sorghum in reduced tillage systems. Two conservation tillage methods (ripping and planting basins) combined factorially with seven mulch levels (0, 0.5, 1, 2, 4, 8 and 10 t ha -1) were compared with conventional mouldboard ploughing. The experiment was run for four consecutive growing seasons allowing for a rotation of maize, cowpea, sorghum and maize in some fields used in the study. Crop yields were determined across all tillage and mulch combinations in each year. Tillage system had no significant effect on maize yield while maize grain yield increased with increase in mulch cover in seasons that had below average rainfall. Mulching at 2-4 t ha -1 gave optimum yields in seasons with below average rainfall. Tillage system and mulching had no significant effect on cowpea yield when soil moisture was not limiting. However, the ripper and basin systems had 142 and 102% more cowpea grain than the conventional system in 2006/2007 because of differences in planting dates used in three systems and poor rainfall distribution. The conventional and ripper systems gave 26 and 38% more sorghum grain than the basin system. Rotating maize with cowpea and sorghum resulted in 114, 123 and 9% more grain than first year maize, maize-maize monocrop and maize-cowpea-maize in the conventional system. In the ripper system, maize-cowpea-sorghum-maize rotation gave 98, 153 and 39% more grain than first year maize, maize-maize monocrop and maize-cowpea-maize rotation. In the basin system, maize-cowpea-sorghum-maize rotation gave 274, 240 and 43% more grain than first year maize, maize-maize monocrop and maize-cowpea-maize rotation. However, long term studies under different soil, climatic and socio-economic conditions still need to be conducted to substantiate the observations made in the reported study.
  • Authors:
    • Mkwinda, S.
    • Aune,J. B.
    • Ngwira, A. R.
  • Source: Field Crops Research
  • Volume: 132
  • Year: 2012
  • Summary: Low crop yields due to continuous monocropping and deteriorating soil health in smallholder farmers' fields of sub-Saharan Africa have led to a quest for sustainable production practices with greater resource use efficiency. The aim of the study was to elucidate the short term effects of conservation agriculture (CA) systems on soil quality, crop productivity and profitability. In Balaka market and Ntonda sections of Manjawira Extension Planning Area (EPA), in Ntcheu district, central Malawi, we compared continuous monocropped maize (Zea mays) under conventional tillage practice (CP) with different CA systems in continuous monocropped maize (CAM) and intercropping with pigeonpea (Cajanus cajan) (CAMP), Mucuna pruriens (CAMM), and Lablab purpureus (L) (Sweet) (CAML). The study was conducted from 2008 to 2011 in 72 plots in 24 farmers' fields. In Balaka market section CA plots with maize + legumes produced up to 4.3 Mg ha(-1) of vegetative biomass against 3.5 Mg ha for maize alone in CP. In Ntonda section CA plots with maize + legumes produced up to 4.6 Mg ha(-1) of vegetative biomass against 2.4 Mg ha(-1) for maize alone in CP. In both sections, during the entire study period. CA did not have a negative effect on crop yields. During the drier seasons of 2009110 and 2010/11, CA had a positive effect on maize grain yield at both sites (average yield of 4.4 and 3.3 Mg ha(-1) in CA and CP respectively). However, associating maize with legumes reduced maize yields compared to CAM particularly in drier years of 2009-10 and 2010-11. Farmers spent at most 47 days ha(-1) producing maize under CA systems compared to 65 days ha(-1) spent under conventional tillage practices. However, total variable costs were higher in CA systems compared to conventional practice (at most US$416 versus US$344 ha(-1)). CAMP resulted in more than double gross margin compared to CPM (US$705 versus uS$344 hat). Infiltration estimated as time to pond was highest in CA maize legume intercrops (8.1 s) than CP (6.8 s). Although it was not feasible to directly estimate effects on water balances of these farmer-managed experiments, it can be assumed that the yield differences between CA and CP could be attributed to tillage and crop residue cover since other farm operations were generally the same. Intercropping maize and pigeonpea under CA presents a win-win scenario due to crop yield improvement and attractive economic returns provided future prices of maize and pigeonpea grain remain favourable. (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • De Neve, S.
    • Sleutel, S.
    • Ngwira, A.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 92
  • Issue: 3
  • Year: 2012
  • Summary: Conservation agriculture (CA) characterised by minimal soil disturbance, permanent soil surface cover by dead or living plants and crop rotations is one way of achieving higher soil organic carbon (C) in agricultural fields. Sandy loam and loamy soil samples from zero tillage (ZT) and conventional tillage (CT) plots were taken from farmers' fields during the dry season in August 2006. Soil organic carbon (SOC) and soil organic nitrogen (SON), microbial biomass carbon (MB-C) and microbial biomass nitrogen (MB-N), C mineralization and SOC distribution in particle size fractions in 0-20 cm layer were evaluated. Forty eight farmers' fields were randomly sampled at four different locations in Central and Northern Malawi, representing ZT plots maintained for a different number of years, and ten fields under CT with similar soil type and crop grown were selected. SOC and SON in ZT fields were 44 and 41 % (4 years ZT) and 75 and 77 % (5 years ZT) higher, respectively, than CT plots. MB-C and MB-N in ZT fields were 16 and 44 % (4 years ZT) and 20 and 38 % (5 years ZT) higher, respectively, than CT plots. However, MB-C and MB-N in ZT fields were 27 and 25 % (2 years ZT) and 17 and 9 % (3 years ZT) lower than in CT plots. The proportion of the total organic C as microbial biomass C was relatively higher under CT than ZT treatments. The higher SOC and MB-C content in the ZT fields resulted in 10, 62, 57 % higher C mineralization rate in ZT plots of 3, 4 and 5 years of loamy sand soils and 35 % higher C mineralization rate in ZT plot of 2 years than CT of sandy loam soils in undisturbed soils in the laboratory. Simulating plough from the undisturbed soils that were used for C mineralization experiment resulted in linear curves indicating that all organic C was already depleted during the first incubation period. The relative distribution of soil organic matter (SOM) in silt and clay size fractions was strongly correlated (r = 0.907 and P a parts per thousand currency sign 0.01) with silt percentages. Easily degradable carbon pool (C-A,C-f) was correlated (r = 0.867 and P a parts per thousand currency sign 0.05) with organic carbon in sand size fraction. In developing viable conservation agriculture practices to optimize SOC content and long-term sustainability of maize production systems, priority should be given to the maintenance of C inputs, crop rotations and associations and also to reduced soil disturbance by tillage.
  • Authors:
    • Larsen, S. E.
    • Kristensen, K.
    • Elsgard, L.
    • Blicher-Mathiesen, G.
    • Schäfer, C. -M
    • Hoffmann, C. C.
    • Petersen, S. O.
    • Torp, S. B.
    • Greve, M. H.
  • Source: Biogeosciences
  • Volume: 9
  • Issue: 1
  • Year: 2012
  • Summary: The use of organic soils by agriculture involves drainage and tillage, and the resulting increase in C and N turnover can significantly affect their greenhouse gas balance. This study estimated annual fluxes of CH4 and N2O, and ecosystem respiration (R-eco), from eight organic soils managed by agriculture. The sites were located in three regions representing different landscape types and climatic conditions, and three land use categories were covered (arable crops, AR, grass in rotation, RG, and permanent grass, PG). The normal management at each site was followed, except that no N inputs occurred during the monitoring period from August 2008 to October 2009. The stratified sampling strategy further included six sampling points in three blocks at each site. Environmental variables (precipitation, PAR, air and soil temperature, soil moisture, groundwater level) were monitored continuously and during sampling campaigns, where also groundwater samples were taken for analysis. Gaseous fluxes were monitored on a three-weekly basis, giving 51, 49 and 38 field campaigns for land use categories AR, PG and RG, respectively. Climatic conditions in each region during monitoring were representative as compared to 20-yr averages. Peat layers were shallow, typically 0.5 to 1 m, and with a pH of 4 to 5. At six sites annual emissions of N2O were in the range 3 to 24 kg N2O-N ha(-1), but at two arable sites (spring barley, potato) net emissions of 38 and 61 kg N2O-N ha(-1) were recorded. The two high-emitting sites were characterized by fluctuating groundwater, low soil pH and elevated groundwater SO42- concentrations. Annual fluxes of CH4 were generally small, as expected, ranging from 2 to 4 kg CH4 ha(-1). However, two permanent grasslands had tussocks of Juncus effusus L. (soft rush) in sampling points that were consistent sources of CH4 throughout the year. Emission factors for organic soils in rotation and with permanent grass, respectively, were estimated to be 0.011 and 0.47 gm(-2) for CH4, and 2.5 and 0.5 gm(-2) for N2O. This first documentation of CH4 and N2O emissions from managed organic soils in Denmark confirms the levels and wide ranges of emissions previously reported for the Nordic countries. However, the stratified experimental design also identified links between gaseous emissions and site-specific conditions with respect to soil, groundwater and vegetation which point to areas of future research that may account for part of the variability and hence lead to improved emission factors or models.
  • Authors:
    • Prasuhn, V.
  • Source: Soil & Tillage Research
  • Volume: 120
  • Year: 2012
  • Summary: The positive effects of soil conserving farming methods have mostly been demonstrated using small test plots. The present study is aimed at confirming that they also occur on the catchment scale. The impact of crops and soil tillage practises on the extent of soil erosion was determined in 203 crop fields over 10 years in the Swiss Midlands. Soil erosion totalled 1969 t or 0.75 t ha(-1) yr(-1). Most erosion took place in winter wheat fields (33%), which accounted for 22% of the crop area. Second and third most erosion was observed in potato (26%) and fallow (14%) fields. By far the highest mean soil loss was found for potatoes, at 2.87 t ha(-1) yr(-1). Fallow (1.06 t ha(-1) yr(-1)) and winter wheat (1.05 t ha(-1) yr(-1)) fields were also relatively susceptible to soil erosion. In contrast, values for soil loss below mean were observed for maize (0.44 t ha(-1) yr(-1)), sugar beet (0.27 t ha(-1) yr(-1)), and rape seed (0.39 t ha(-1) yr(-1)). 88% of soil erosion took place on plough tilled land (PT), 9% on non-ploughed land with less than 30% surface residue cover (RT), 1% on mulch-tilled land with more than 30% surface residue cover (MT), and 2% in non-tilled or strip-tilled land with >30% soil cover (NT). At 0.07 and 0.12 t ha(-1) yr(-1), respectively, the mean soil loss in MT and NT fields was more than an order of magnitude lower than that under PT (1.24 t ha(-1) yr(-1)). Field mappings confirmed the positive effects of the soil conserving soil tillage practises. The risk of soil erosion was significantly influenced by crop rotation. The carry-over effects should be taken into account when studying the effects of cropping methods on soil erosion. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Shah, S. C.
    • Chen, Z. S.
    • Adhikari, K. R.
    • Ghimire, R.
    • Dahal, K. R.
  • Source: Paddy and Water Environment
  • Volume: 10
  • Issue: 2
  • Year: 2012
  • Summary: Despite being a major domain of global food supply, rice-wheat cropping system is questioned for its contribution to carbon flux. Enhancing the organic carbon pool in this system is therefore necessary to reduce environmental degradation and maintain agricultural productivity. A field experiment (November 2002-March 2006) evaluated the effects of soil management practices such as tillage, crop residue, and timing of nitrogen (N) application on soil organic carbon (SOC) sequestration in the lowland of Chitwan Valley of Nepal. Rice ( Oryza sativa L.) and wheat ( Triticum aestivum L.) were grown in rotation adding 12 Mg ha -1 y -1 of field-dried residue. Mung-bean ( Vigna radiata L.) was grown as a cover crop between the wheat and the rice. Timing of N application based on leaf color chart method was compared with recommended method of N application. At the end of the experiment SOC sequestration was quantified for five depths within 50 cm of soil profile. The difference in SOC sequestration between methods of N application was not apparent. However, soils sequestered significantly higher amount of SOC in the whole profile (0-50 cm soil depth) with more pronounced effect seen at 0-15 cm soil depth under no-tillage as compared with the SOC under conventional tillage. Crop residues added to no-tillage soils outperformed other treatment interactions. It is concluded that a rice-wheat system would serve as a greater sink of organic carbon with residue application under no-tillage system than with or without residue application when compared to the conventional tillage system in this condition.
  • Authors:
    • Oliveira, E. B. de
    • Moraes, A. de
    • Pelissari, A.
    • Reis, E. F. dos
    • Ruaro, L.
  • Source: Pesquisa Agropecuária Brasileira
  • Volume: 47
  • Issue: 4
  • Year: 2012
  • Summary: The objective of this work was to assess the effect of soil management systems and winter cover crops on the number of propagules of Fusarium spp. in soil, the incidence of sudden death syndrome (SDS), and the productivity of the soybean cultivars CD 206 and FT Fenix. Two experiments were carried out in the 2006/2007 and 2007/2008 crop years. The experimental design was a randomized complete block in a split-split plot arrangement, with three replicates. Two soil tillage systems were evaluated: no-tillage and plowed soil at a depth of 25 cm. The soil covers used were: black oat, with two planting densities; black oat+vetch; ryegrass; and fallow. The incidence of the disease in the 2006/2007 crop year in the cultivar FT Fenix was lower than in CD 206. In the 2007/2008 crop, there was no significant difference. There was an increase in productivity, of 125 kg ha -1, in the plowed treatment, when compared to no-tillage. The cover with black oat+vetch showed a higher number of propagules of Fusarium spp. in soil in the 2006/2007 crop year. However, in the second year, this difference was not observed. The soil management systems and winter cover crops used do not influence the incidence of SDS in soybean cultivars or the number of Fusarium spp. propagules in soil. The plowed system provides an increase in soybean yield in the second year of management.
  • Authors:
    • Gonzalez, B.
    • Rodriguez, E.
    • Campos, M.
  • Source: Bulletin of Insectology
  • Volume: 65
  • Issue: 1
  • Year: 2012
  • Summary: The use of cover crops is the most effective method to combat soil degradation due to erosion in olive cropping in Spain. Within the framework of Integrated Pest Management (IPM), a compelling question is how cover crops would affect elements of the olive-agroecosystem such as natural enemies. Accordingly, the objective of this study was to examine the effects of cereal cover cropping on natural enemy communities in olive groves. Samples of the anthropod communities were collected in olive groves under tillage and cover cropping systems at five different locations in the same province. Cereal cover crops significantly increased the abundance of parasitoids in the olive canopy, especially Ageniaspis fuscicollis Dalman (Hymenoptera Encyrtidae) a parasitoid of the olive moth Prays oleae Bernard (Lepidoptera Yponomeutidae), the most common insect pest of olive trees. However, parasitoid abundance and structure depended on olive grove location suggesting the importance of crop surroundings in parasitoid community dynamics. Predators numbers were slightly higher in tilled olive groves but no significant differences were found between the two soil management systems.
  • Authors:
    • Feng, G.
    • Wendling, L.
    • Sharratt, B.
  • Source: Aeolian Research
  • Volume: 5
  • Year: 2012
  • Summary: Winter wheat - summer fallow is the crop rotation used on more than 1.5 million ha in the Pacific Northwest United States. Land maintained using conventional summer fallow is susceptible to wind erosion because multiple tillage operations during the fallow period expose the soil to high winds. Alternative management strategies are needed that protect the soil surface from erosion during summer fallow. Surface characteristics were examined after subjecting the loessial soil to seven (conventional), five (reduced), three (minimum), and zero (no) tillage operations during the fallow period. Surface residue biomass and roughness and soil crust, aggregation, strength, and water content were measured after tillage and sowing operations. No tillage resulted in a more persistent and thicker soil crust and greater residue cover, silhouette area index (SAI), and penetration resistance than conventional and reduced tillage. For those treatments subject to tillage, minimum tillage resulted in a thicker soil crust and greater residue cover, SAI, ridge roughness, mean aggregate diameter, and penetration resistance as compared to conventional or reduced tillage after primary tillage. Near the end of the fallow period, minimum tillage resulted in 15% greater residue cover than conventional tillage. Soil loss from minimum tillage is expected to be 50% of conventional tillage based upon these differences in residue cover. This study suggests that minimum tillage is an alternative strategy to conventional tillage for reducing wind erosion in the wheat-fallow region of the Pacific Northwest. Published by Elsevier B.V.