• Authors:
    • Schneider, D. A.
    • Lamb, D. W.
    • Stanley, J. N.
  • Source: PRECISION AGRICULTURE
  • Volume: 15
  • Issue: 5
  • Year: 2014
  • Summary: An integrated active optical, and passive thermal infrared sensing system was deployed on a low-level aircraft (50 m AGL) to record and map the simple ratio (SR) index and canopy temperature of a 230 ha cotton field. The SR map was found to closely resemble that created by a RapidEye satellite image, and the canopy temperature map yielded values consistent with on-ground measurements. The fact that both the SR and temperature measurements were spatially coincident facilitated the rapid and convenient generation of a direct correlation plot between the two parameters. The scatterplot exhibited the typical reflectance index-temperature profile generated by previous workers using complex analytical techniques and satellite imagery. This sensor offers a convenient and viable alternative to other forms of optical and thermal remote sensing for those interested in plant and soil moisture investigations using the 'reflectance index-temperature' space concept.
  • Authors:
    • Kundu, S.
    • Subba Rao, A.
    • Singh, R. C.
    • Lenka, N. K.
    • Lenka, S.
    • Raghuwansi, J.
    • Patidar, C. P.
  • Source: CURRENT SCIENCE
  • Volume: 107
  • Issue: 7
  • Year: 2014
  • Summary: Biomass burning is a major contributor to the atmospheric carbon budget and increases the concentration of many trace gases apart from the adverse effects on soil properties. However, in many parts of India, crop residue burning is a recurrent and widespread practice for disposal of the residues after harvest of the previous crop to facilitate sowing of the succeeding crop. The residue burning on a larger scale also leads to severe atmospheric pollution. Against this backdrop, the present work was conducted to study the effect of wheat (Triticum aestivum) residue burning on soil properties and assess the potential greenhouse gas emission from burning of such residues on a regional scale. The study was taken up on farmers' field in Bhopal district, Madhya Pradesh, with two residue disposal methods, viz. residue burning and residue removal, for comparison with respect to their effect on soil properties and the greenhouse gas emission potential. No significant difference was observed between both methods in terms of soil organic carbon, inorganic carbon and available P content at 0-15 and 15-30 cm soil depths. Though residue burning showed favourable effect on available K content, there was reduction in the available N content in the 15-30 cm soil depth. Residue burning did not show significant effect on soil biological activity as estimated from fluorescence diacetate test. On the other hand, there was a significant adverse effect on soil structure and labile carbon content. Residue burning was estimated to result in the emission of 379 Gg C equivalent for India and 14 Gg C equivalent for MP.
  • Authors:
    • Pandey, R. N.
    • Sahoo, R. N.
    • Mahajan, G. R.
    • Gupta, V. K.
    • Kumar, D.
  • Source: PRECISION AGRICULTURE
  • Volume: 15
  • Issue: 5
  • Year: 2014
  • Summary: In situ, non-destructive and real time mineral nutrient stress monitoring is an important aspect of precision farming for rational use of fertilizers. Studies have demonstrated the ability of remote sensing to monitor nitrogen (N) in many crops, phosphorus (P) and potassium (K) in very few crops and none so far to monitor sulphur (S). Specially designed (1) fertility gradient experiment and (2) test crop experiments were used to check the possibility of mineral N-P-S-K stress detection using airborne hyperspectral remote sensing. Leaf and canopy hyperspectral reflectance data and nutrient status at booting stage of the wheat crop were recorded. N-P-S-K sensitive wavelengths were identified using linear correlation analysis. Eight traditional vegetation indices (VIs) and three proposed (one for P and two for S) were evaluated for plant N-P-S-K predictability. A proposed VI (P_1080_1460) predicted P content with high and significant accuracy (correlation coefficient (r) 0.42 and root means square error (RMSE) 0.180 g m(-2)). Performance of the proposed S VI (S_660_1080) for S concentration and content retrieval was similar whereas prediction accuracies were higher than traditional VIs. Prediction accuracy of linear regressive models improved when biomass-based nutrient contents were considered rather than concentrations. Reflectance in the SWIR region was found to monitor N-P-S-K status in plants in combination with reflectance at either visible (VIS) or near infrared (NIR) region. Newly developed and validated spectral algorithms specific to N, P, S and K can further be used for monitoring in a wheat crop in order to undertake site-specific management.
  • Authors:
    • DeFries, R. S.
    • Small, C.
    • Galford, G. L.
    • Robertson, A. W.
    • Jain, M.
    • Mondal, P.
  • Source: CLIMATIC CHANGE
  • Volume: 126
  • Issue: 1-2
  • Year: 2014
  • Summary: India is predicted to be one of the most vulnerable agricultural regions to future climate changes. Here, we examined the sensitivity of winter cropping systems to inter-annual climate variability in a local market and subsistence-based agricultural system in central India, a data-rich validation site, in order to identify the climate parameters to which winter crops - mainly wheat and pulses in this region - might be sensitive in the future. We used satellite time-series data to quantify inter-annual variability in multiple climate parameters and in winter crop cover, agricultural census data to quantify irrigation, and field observations to identify locations for specific crop types. We developed three mixed-effect models (250 m to 1 km scale) to identify correlations between crop cover (wheat and pulses) and twenty-two climate and environmental parameters for 2001-2013. We find that winter daytime mean temperature (November-January) is the most significant factor affecting winter crops, irrespective of crop type, and is negatively associated with winter crop cover. With pronounced winter warming projected in the coming decades, effective adaptation by smallholder farmers in similar landscapes would require additional strategies, such as access to fine-scale temperature forecasts and heat-tolerant winter crop varieties.
  • Authors:
    • Thierfelder, C.
    • Aune, J. B.
    • Ngwira, A. R.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 143
  • Year: 2014
  • Summary: Adoption of conservation agriculture (CA) is increasingly being promoted as a way of adapting agricultural systems to increasing climate variability, especially for areas such as southern Africa where rainfall is projected to decrease. The DSSAT crop simulation models can be a valuable tool in evaluating the effects of CA which are viable both economically and environmentally. Our objectives were: (1) to evaluate the ability of DSSAT to predict continuous maize (Zea mays L.) yield for conventional tillage (CT) and CA systems as well as maize yield for a CA maize-cowpea (Vigna unguiculata) rotation on an Oxic rhodustalf (2) to use DSSAT to project weather effect of climate change on yield, economic returns and risk in CT and CA systems. The DSSAT model was calibrated using data from 2007-2008 season and validated against independent data sets of yield of 2008-2009 to 2011-2012 seasons. Simulations of maize yields were conducted on projected future weather data from 2010 to 2030 that was generated by RegCM4 using the A1B scenario. The DSSAT model calibration and validation showed that it could be used for decision-making to choose specific CA practices especially for no-till and crop residue retention. Long term simulations showed that maize-cowpea rotation gave 451kgha-1 and 1.62kgmm-1 rain more maize grain yield and rain water productivity, respectively compared with CT. On the other hand, CT (3131-5023kgha-1) showed larger variation in yield than both CA systems (3863kgha-1 and 4905kgha-1). CT and CA systems gave 50% and 10% cumulative probability of obtaining yield below the minimum acceptable limit of 4000kgha-1 respectively suggesting that CA has lower probability of low yield than CT, thus could be preferred by risk-averse farmers in uncertain climatic conditions. Using similar reasoning, Mean-Gini Dominance analysis showed the dominancy of maize-cowpea rotation and indicated it as the most efficient management system. This study therefore suggests that CA, especially when all three principles are practiced by smallholders in the medium altitude of Lilongwe and similar areas, has the potential to adapt the maize based systems to climate change. Use of DSSAT simulation of the effects of CA was successful for no-till and crop residue retention, but poor for crop rotation. Refinement of crop rotation algorithm in DSSAT is recommended.
  • Authors:
    • Adhya, T. K.
    • Singh Bohra, J.
    • Agrawal, M.
    • Pandey, D.
    • Bhattacharyya, P.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 143
  • Year: 2014
  • Summary: In order to utilize agricultural soils as an option to offset atmospheric carbon, it is essential to ascertain the degree of stability of the accrued carbon. A two step acid hydrolysis technique was used to separate labile and recalcitrant carbon pools in soil upto 30cm depth to analyze their responses to different tillage managements after eight years of continuous practice in a sub-humid tropical rice-wheat system of Indo-Gangetic plains. There were four tillage practices; tillage before sowing/transplantation of every crop (RCT-WCT), tillage before transplanting of rice but no tillage before sowing the succeeding wheat crop (RCT-WNT), tillage before sowing of wheat but no tillage before sowing of rice (RNT-WCT), and no tillage before sowing of rice as well as wheat (RNT-WNT). It was observed that reduction in tillage frequency enhanced the total and recalcitrant carbon contents in soil with the maximum rate of sequestration recorded under RNT-WNT (0.59tCha-1yr-1). The fraction of carbon translated into recalcitrant pool was constant under all the tillage combinations indicating that carbon stabilization was dependent predominantly on organic matter input in the rice-wheat system. Conventional tillage on the other hand caused loss of carbon from the soil as observed by reduction in total soil carbon content under RCT-WCT. Reduction in recalcitrant carbon content under RCT-WCT further indicated that acid hydrolysis might not represent long term carbon accumulation reliably. Concentration of phenolics in labile pool increased under RNT-WNT, RCT-WNT and RNT-WCT practices which also had higher total and recalcitrant carbon pools. This indicated towards contribution of phenolics in carbon stabilization in the soil. Results of the present study further suggested that adoption of no till agriculture in the region offers significant carbon sequestration opportunity under proper agricultural management.
  • Authors:
    • Mahan, A.
    • Finlayson, J.
    • Payton, S.
    • Xue, P.
    • Rudd, Qing wu
    • Liu, J.
    • Reddy, S.
    • Lu
    • Akhunova, S.
    • Holalu, Nan yan
  • Source: JOURNAL OF PLANT PHYSIOLOGY
  • Volume: 171
  • Issue: 14
  • Year: 2014
  • Summary: Hard red winter wheat crops on the U.S. Southern Great Plains often experience moderate to severe drought stress, especially during the grain filling stage, resulting in significant yield losses. Cultivars TAM 111 and TAM 112 are widely cultivated in the region, share parentage and showed superior but distinct adaption mechanisms under water-deficit (WD) conditions. Nevertheless, the physiological and molecular basis of their adaptation remains unknown. A greenhouse study was conducted to understand the differences in the physiological and transcriptomic responses of TAM 111 and TAM 112 to WD stress. Whole-plant data indicated that TAM 112 used more water, produced more biomass and grain yield under WD compared to TAM 111. Leaf-level data at the grain filling stage indicated that TAM 112 had elevated abscisic acid (ABA) content and reduced stomatal conductance and photosynthesis as compared to TAM 111. Sustained WD during the grain filling stage also resulted in greater flag leaf transcriptome changes in TAM 112 than TAM 111. Transcripts associated with photosynthesis, carbohydrate metabolism, phytohormone metabolism, and other dehydration responses were uniquely regulated between cultivars. These results suggested a differential role for ABA in regulating physiological and transcriptomic changes associated with WD stress and potential involvement in the superior adaptation and yield of TAM 112.
  • Authors:
    • Warland, J.
    • Furon, A.
    • Wagner-Riddle, C.
    • Risk, N.
    • Blodau, C.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 78
  • Issue: 1
  • Year: 2014
  • Summary: In cold climates, large emissions of N2O have been found to occur from agricultural soils at spring thaw. Of fundamental importance is determining whether the majority of N2O emitted is produced before spring thaw and then released, or if it is produced at the onset of spring thaw. It has been suggested that physical release comprises the often observed first N2O emission event at thaw, while the subsequent event is likely due to enhanced denitrification. To test this, the objective of this study was to compare changes in soil profile N2O content over time to N 2O surface fluxes at spring thaw measured using the micrometeorological flux-gradient technique, which allowed for capturing of the dynamic nature of N2O flux during thawing. Measurements were conducted from October 2010 to May 2011, in a 1.5-ha plot (conventional till) in Ontario, Canada. Soil profile measurements included water content, temperature, and N2O gas concentration weekly overwinter and daily during the main spring-thaw. Soil N2O mass in gaseous and aqueous forms was estimated. Soil N2O mass in the 0- to 70-cm profile reached a total 23 mg N2O m-2 and decreased rapidly during spring thaw when two events of heightened flux occurred. During the first event, surface N2O fluxes corresponded to 24% of the change in mass, however during the second event N2O fluxes were five times larger. Our results provide the first quantitative evidence for the suggestion that N2O spring thaw emission is comprised by a first event mostly due to physical release, followed by a second event with fluxes predominantly due to de novo production. The physical release event was simultaneous with large decreases in N2O trapped in the top soil layer and not due to N2O trapped at depth. Exact apportioning of surface flux into N2O sources (i.e., accumulated in profile vs. newly produced) is not possible, but assuming that most of the first emission event was due to physical release gives a rough estimate of 22% for the contribution of physical release.
  • Authors:
    • Shangguan, Z.
    • Yang, Q.
    • Deng, L.
    • Shao, R.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 143
  • Year: 2014
  • Summary: As the largest reservoir of terrestrial carbon (C), soil is a source or sink for atmospheric carbon dioxide (CO2). Understanding the processes whereby soil CO2 is released into the atmosphere as a result of using inorganic nitrogen (N) fertilizers may provide us with knowledge of processes to offset the increasing concentration of CO2. The main objective of this study was to investigate the effects of different N levels on soil CO2 efflux with one controlled experiment. A field experiment was carried out in a non-irrigated winter wheat (Triticum aestivum L.) - cropland in Northwest China to investigate the effects of N fertilization on soil CO2 efflux in two consecutive growing seasons (2007-2009). The soil CO2 efflux to which N was applied at four different levels (0, 90, 180, and 360kg Nha-1) was measured during the growing seasons in 2007-2009. At most growth stages during the growing season, the soil CO2 efflux increased significantly with increased N application. The effect of N fertilization on the cumulative soil CO2 efflux was obvious. In the 10-20cm soil layer, the seasonal variations in soil CO2 effluxes were influenced by soil temperature (ST) rather than by soil water content (SWC). When ST >20°C, however, the low soil CO2 efflux was mainly due to low SWC, which was close to the permanent wilting point (8.5g H2O 100g dry soil-1). In addition, soil CO2 effluxes after anthesis were higher than those at seedling stage and were highest nearby anthesis stage. The results indicated that N fertilization probably had a positive effect on both the seasonal and cumulative soil CO2 effluxes during the growing season.
  • Authors:
    • Liang, L.
    • Jia, Z.
    • Wang, X.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 69
  • Issue: 5
  • Year: 2014
  • Summary: Field experiments were conducted from 2008 to 2010 in the Weibei Highlands of China to study the effects of straw incorporation on soil moisture, evapotranspiration (ET), and rainfall-use efficiency (RUE) of maize (Zea mays L.) under semiarid conditions in dark loessial soil. The straw application rates were at low straw ([LS] 4.5 t ha(-1)), medium straw ([MS] 9 t ha(-1)), and high straw ([HS] 13.5 t ha(-1)) rates combined with fixed levels of chemical fertilizers compared with only chemical fertilizers. Straw incorporation significantly increased surface soil moisture at the grain filling stage of maize and significantly improved RUE in the whole growth period of maize. Evapotransipiration at the ten leaf collar to tasseling and the grain filling to maturity stages of maize were significantly increased by straw incorporation. However, ET at the tasseling to grain filling stage of maize was significantly reduced by straw incorporation. Medium straw and HS treatments significantly improved surface soil moisture at the tasseling stage of maize and RUE at the five leaf collar to maturity stage of maize. Increasing straw application rates significantly reduced ET at the grain filling to maturity stage of maize. With increasing experimental years, LS treatment significantly improved surface soil moisture at the five leaf collar to tasseling stage of maize and RUE at the five and ten leaf collar stage of maize, MS treatment significantly increased surface soil moisture at the five and ten leaf collar stages of maize, and HS treatment significantly reduced ET at the sowing to five leaf collar stage of maize. We conclude that a reasonable combination application of straw and chemical fertilizers could make full use of surface soil moisture, inhibit soil evaporation, reduce the ineffective evaporation of crop, and increase RUE at a different growth period of maize and grain yield. In this experiment, the optimum straw application rate for improving RUE and grain yield was MS treatment.