• Authors:
    • McDaniel, M. D.
    • Wickings, K.
    • Salam, D. S.
    • Grandy, A. S.
    • Culman, S. W.
    • Snapp, S. S.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 179
  • Year: 2013
  • Summary: Litter decomposition dynamics are influenced by soil nutrient status, yet the specific effects of soil nitrogen (N) on litter decomposition in agricultural systems are not well understood. We explored litter decomposition and related soil organic matter dynamics in no-till, corn-based Midwestern U.S. cropping systems receiving 0, 134, and 291 kg N ha -1 y -1. We found that total soil carbon (C) and N, light fraction organic matter, and permanganate oxidizable C were similar among treatments, but N fertilization at rates of 134 and 291 kg N ha -1 y -1 reduced potentially mineralizable C by as much as 37% and 58%, respectively, compared to the unfertilized treatment. Litter mass remaining after one year of field decomposition was greater with wheat litter (37%) than with corn litter (23%), but was not influenced by N fertilizer rate. In litter, N fertilization led to increases in the activities of two hydrolase enzymes involved in simple carbohydrate metabolism (beta-d-cellobiohydrolase and beta-1,4-glucosidase) and periodic increases in one related to N metabolism (beta-1,4-N-acetylglucosaminidase), but had no effects on enzymes regulating the breakdown of aromatic compounds (phenol oxidase), or on enzymes measured in the soil. N fertilization also decreased arthropod densities in decomposing litter. We found contrasting effects of N fertilizer on processes regulating decomposition, but altogether our results were consistent with a limited or nil role for N fertilization in accelerating litter and soil C turnover, and thus do not support N fertilization as a contributor to depletion of C stocks in agricultural soils.
  • Authors:
    • Norton, J. B.
    • Hurisso, T. T.
    • Norton, U.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 181
  • Year: 2013
  • Summary: Conversion of native prairie land for agricultural production has resulted in significant loss and redistribution of soil organic matter (SOM) in the soil profile ultimately leading to declining soil fertility in a low-productivity semiarid agroecosystem. Improved understanding of such losses can lead to development of sustainable land management practices that maintain soil fertility and enhance soil quality. This study was conducted to determine whether conservation practices impact soil profile carbon (C) and nitrogen (N) accumulation in central High Plains. Soil samples were taken at four-depth increments to 1.2 m in July of 2011 from five unfertilized fields under long-term management with varying degrees of soil disturbance: (1) historic wheat ( Triticum aestivum)-fallow (HT) - managed with tillage alone, (2) conventional wheat-fallow (CT) - input of herbicides for weed control and fewer tillage operation than historic wheat-fallow, (3) no-till wheat-fallow (NT) - not plowed since 2000 and herbicides used for weed control, (4) grass-legume mixture - established in 2005 as in the Conservation Reserve Program (CRP), and (5) native mixed grass prairie (NP) - representing a relatively undisturbed reference location. Cumulative soil organic C (SOC) was not significantly different among the three wheat-fallow systems when the whole profile (0-120 cm) was analyzed. However, SOC, dissolved organic C (DOC), and total soil N contents decreased in the direction NP > CRP ≥ NT > HT ≥ CT in the surface 0-30 cm depth. In the surface 0-30 cm depth, estimated annual SOC storage rate averaged 0.28 Mg C ha -1 year -1 since the cessation of tillage in 2000 and 0.58 Mg C ha -1 year -1 since the establishment of CRP grass-legume mixture in 2005. Cumulative soil inorganic C (SIC) accumulation ranged between 8.1 and 24.9 Mg ha -1and was greatest under wheat-fallow systems, particularly at deeper soil layers, relative to the perennial systems (NP and CRP). Results from this study suggest that repeated soil disturbance induced by cropping and fallow favored large accumulation of SIC which presence may result in decline in soil fertility and productivity; whereas conversion from tilled wheat-fallow to CRP grass-legume mixture offers great SOC storage potential relative to NT wheat-fallow practices.
  • Authors:
    • Miller, P. R.
    • O'Dea, J. K.
    • Jones, C. A.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 68
  • Issue: 4
  • Year: 2013
  • Summary: Replacing summer fallow practices with annual legumes as green manures (LGMs) may increase the sustainability of northern Great Plains wheat (Triticum aestivum L.) systems. Viability hinges on soil water use management and realizing biologically fixed nitrogen (N) benefits. Plot-scale research has shown that managing LGMs with first-flower stage termination and no-till practices conserves soil water and that rotational N benefits can increase wheat grain quality Nonetheless, farmer adoption of LGMs has been negligible. To better understand this practice and its regional adoption potential, we conducted a participatory on-farm assessment of no-till LGM versus summer fallow wheat rotations in north-central Montana. Soil water and nitrate (NO3) levels to 0.9 m (3 ft), potentially mineralizable N (PMN) to 0.3 m (1 ft), wheat yields, conservation potential, and producer adoption challenges were assessed at five farmer-managed, field-scale sites. Compared to fallow, LGM treatment diminished mean wheat yield by 6% (0.24 Mg ha(-1) [3.7 bu ac(-1)]), diminished grain protein by 9 g kg(-1) when wheat was fertilized with N (p = 0.01), and increased grain protein by 5 g kg(-1) when wheat was unfertilized (p = 0.08). Small soil water depletions in LGM treatments below fallow at wheat seeding (17%; 30 mm [1.2 in]) and near-record high rainfall during the wheat growing season (280 to 380 mm [11 to 14 in]) suggest that LGMs likely did not limit soil water available to wheat in this study. Soil NO3 levels following LGMs were 29% to 56% less than summer fallow at wheat seeding, and conversely, greater PMN was detected in LGM treatments at 3 of 5 sites. We theorize that N mineralization from LGMs was insubstantial by wheat seeding due to dry soil conditions and low LGM biomass N contributions, consequently affecting wheat yield potential due to limited early season soil N availability. LGMs increased average use efficiency of available N by 24% during the wheat year and increased total residue carbon (C) and N returned to soils by 260 and 26 kg ha(-1) (232 and 23 lb ac(-1)), respectively, after two years. Our results illustrated that farmers viably managed LGM soil water use with early termination and no-till practices but that LGM adoption may be hindered by a lack of immediate wheat yield or protein benefits from legume-N and seed costs for LGMs. Appropriate incentives, management strategies, and yield benefit expectations (short versus long term) should be fostered to increase the adoption potential of this N-economizing soil and water conservation strategy.
  • Authors:
    • Mahanta, D.
    • Tuti, M. D.
    • Gupta, H. S.
    • Bhatt, J. C.
    • Bisht, J. K.
    • Pandey, S. C.
    • Bhattacharyya, R.
    • Mina, B. L.
    • Singh, R. D.
    • Chandra, S.
    • Srivastva, A. K.
    • Kundu, S.
  • Source: Agronomy Journal
  • Volume: 105
  • Issue: 1
  • Year: 2013
  • Summary: Carbon retention is a critical issue in arable farming of the Indian Himalayas. This study, conducted from 2001 through 2010 on a sandy clay loam soil, evaluated the effect of tillage alterations (conventional tillage [CT] and zero tillage [ZT]) and selected irrigation treatments (I1: pre-sowing, I2: pre-sowing + active tillering or crown root initiation, I3: pre-sowing + active tillering or crown root initiation + panicle initiation or flowering, and I4: pre-sowing + active tillering or crown root initiation + panicle initiation or flowering + grain filling), applied at the critical growth stages to rice ( Oryza sativa L.) and wheat ( Triticum aestivum L.) on soil organic C (SOC) retention and its pools, soil aggregation, and aggregate-associated C contents in the 0- to 30-cm soil layer. Results indicate that the plots under ZT had nearly 17 and 14% higher total SOC and particulate organic C contents compared with CT (~9.8 and 3.6 g kg -1 soil) in the 0- to 5-cm soil layer after 9 yr of cropping, despite similar mean aboveground biomass yields of both crops on both CT and ZT plots. Tillage had no effect on C pools in the subsurface layers. Irrigation had positive impact on SOC content in the 0- to 5- and 5- to 15-cm layers. Although the labile pools of SOC were positively affected by ZT, the recalcitrant pool was not. Plots under ZT and I4 also had higher large and small macroaggregates and macroaggregate-associated SOC. Thus, adoption of ZT is the better management option for soil C improvement than CT, and irrigation generally enhances the positive impacts.
  • Authors:
    • Wang, D. P.
    • Zheng, L.
    • Zhang, Z. H.
    • Meng, F. Q.
    • Wu, W. L.
    • Shi, Y. F.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 95
  • Issue: 2
  • Year: 2013
  • Summary: In the North China Plain, a field experiment was conducted to measure nitrous oxide (N2O) and methane (CH4) fluxes from a typical winter wheat-summer maize rotation system under five integrated agricultural management practices: conventional regime [excessive nitrogen (N) fertilization, flood irrigation, and rotary tillage before wheat sowing; CON], recommended regime 1 (balanced N fertilization, decreased irrigation, and deep plowing before wheat sowing; REC-1), recommended regime 2 (balanced N fertilization, decreased irrigation, and no tillage; REC-2), recommended regime 3 (controlled release N fertilizer, decreased irrigation, and no tillage; REC-3), and no N fertilizer (CK). Field measurements indicated that pulse emissions after N fertilization and irrigation contributed 19-49 % of annual N2O emissions. In contrast to CON (2.21 kg N2O-N ha(-1) year(-1)), the other treatments resulted in significant declines in cumulative N2O emissions, which ranged from 0.96 to 1.76 kg N2O-N ha(-1) year(-1), indicating that the recommended practices (e.g., balanced N fertilization, controlled release N fertilizer, and decreased irrigation) offered substantial benefits for both sustaining grain yield and reducing N2O emissions. Emission factors of N fertilizer were 0.21, 0.22, 0.23, and 0.37 % under CON, REC-1, REC-3, and REC-2, respectively. Emissions of N2O during the freeze-thaw cycle period and the winter freezing period accounted for 9.7 and 5.1 % of the annual N2O budget, respectively. Thus, we recommend that the monitoring frequency should be increased during the freeze-thaw cycle period to obtain a proper estimate of total emissions. Annual CH4 fluxes from the soil were low (-1.54 to -1.12 kg CH4-C ha(-1) year(-1)), and N fertilizer application had no obvious effects on CH4 uptake. Values of global warming potential were predominantly determined by N2O emissions, which were 411 kg CO2-eq ha(-1) year(-1) in the CK and 694-982 kg CO2-eq ha(-1) year(-1) in the N fertilization regimes. When comprehensively considering grain yield, global warming potential intensity values in REC-1, REC-2, and REC-3 were significantly lower than in CON. Meanwhile, grain yield increased slightly under REC-1 and REC-3 compared to CON. Generally, REC-1 and REC-3 are recommended as promising management regimes to attain the dual objectives of sustaining grain yield and reducing greenhouse gas emissions in the North China Plain.
  • Authors:
    • Isaev, S.
    • Mavlyanov, D.
    • Esanbekov, M.
    • Khasanova, F.
    • Sultonov, M.
    • Karaev, S.
    • Kobilov, R.
    • Ibragimov, N.
    • Kholov, B.
    • Bekenov, M.
    • Martynova, L.
    • Ibraeva, M.
    • Otarov, A.
    • Yuldashev, T.
    • Glazirina, M.
    • Sommer, R.
    • Abdurahimov, S.
    • Ikramov, R.
    • Shezdyukova, L.
    • Pauw, E. de
  • Source: Agriculture Ecosystems and Environment
  • Volume: 178
  • Year: 2013
  • Summary: Climate change (CC) may pose a challenge to agriculture and rural livelihoods in Central Asia, but in-depth studies are lacking. To address the issue, crop growth and yield of 14 wheat varieties grown on 18 sites in key agro-ecological zones of Kazakhstan, Kyrgyzstan, Uzbekistan and Tajikistan in response to CC were assessed. Three future periods affected by the two projections on CC (SRES A1B and A2) were considered and compared against historic (1961-1990) figures. The impact on wheat was simulated with the CropSyst model distinguishing three levels of agronomic management. Averaged across the two emission scenarios, three future periods and management scenarios, wheat yields increased by 12% in response to the projected CC on 14 of the 18 sites. However, wheat response to CC varied between sites, soils, varieties, agronomic management and futures, highlighting the need to consider all these factors in CC impact studies. The increase in temperature in response to CC was the most important factor that led to earlier and faster crop growth, and higher biomass accumulation and yield. The moderate projected increase in precipitation had only an insignificant positive effect on crop yields under rainfed conditions, because of the increasing evaporative demand of the crop under future higher temperatures. However, in combination with improved transpiration use efficiency in response to elevated atmospheric CO 2 concentrations, irrigation water requirements of wheat did not increase. Simulations show that in areas under rainfed spring wheat in the north and for some irrigated winter wheat areas in the south of Central Asia, CC will involve hotter temperatures during flowering and thus an increased risk of flower sterility and reduction in grain yield. Shallow groundwater and saline soils already nowadays influence crop production in many irrigated areas of Central Asia, and could offset productivity gains in response to more beneficial winter and spring temperatures under CC. Adaptive changes in sowing dates, cultivar traits and inputs, on the other hand, might lead to further yield increases.
  • Authors:
    • Liu, G.
    • Takigawa, M.
    • Zhu, J. G.
    • Tang, H. Y.
    • Kobayashi, K.
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 9
  • Year: 2013
  • Summary: Using a high-resolution (40*40 km) chemical transport model coupled with the Regional Emission inventory in Asia (REAS), we simulated surface ozone concentrations ([O 3]) and evaluated O 3-induced wheat production loss in China and India for the years 2000 and 2020 using dose-response functions based on AOT40 (accumulated [O 3] above 40 ppb) and POD Y (phytotoxic O 3 dose, accumulated stomatal flux of O 3 above a threshold of Y nmol m -2 s -1). Two O 3 dose metrics (90 days AOT40 and POD 6) were derived from European experiments, and the other two (75 days AOT40 and POD 12) were adapted from Asian studies. Relative yield loss (RYL) of wheat in 2000 was estimated to be 6.4-14.9% for China and 8.2-22.3% for India. POD 6 predicted greater RYL, especially for the warm regions of India, whereas the 90 days AOT40 gave the lowest estimates. For the future projection, all the O 3 dose metrics gave comparable estimates of an increase in RYL from 2000 to 2020 in the range 8.1-9.4% and 5.4-7.7% for China and India, respectively. The lower projected increase in RYL for India may be due to conservative estimation of the emission increase in 2020. Sensitivity tests of the model showed that the POD Y -based estimates of RYL are highly sensitive to perturbations in the meteorological inputs, but that the estimated increase in RYL from 2000 to 2020 is much more robust. The projected increase in wheat production loss in China and India in the near future is substantially larger than the uncertainties in the estimation and indicates an urgent need for curbing the rapid increase in surface [O 3] in these regions.
  • Authors:
    • Schjoerring, J. K.
    • Feng, Z. Z.
    • Wang, L.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 178
  • Year: 2013
  • Summary: Wheat is one of the world's most important crops and further increase in wheat yields is required to meet the food demand of the growing global population. It is therefore crucial to know how future climate changes affect wheat yields. The present study quantitatively synthesizes effects of elevated atmospheric CO 2 concentration ([CO 2]) on wheat ( Triticum aestivum L.) physiology and yield by meta-analysis of 59 peer-reviewed papers. The results show that elevated [CO 2] (450-800 ppm) significantly increased wheat grain yield by 24% with 95% bootstrapped confidence intervals of 20-28% across all studies. The increase was dependent on experimental conditions, such as CO 2 exposure method (44% less yield increase in free-air CO 2 enrichment than in enclosure studies), rooting system (smaller response in field compared to pot experiments) and possible coinciding stress factors (low nitrogen and drought). The yield stimulation by elevated [CO 2] was driven by increased photosynthesis (33%) despite reduced stomatal conductance (-23%), Rubisco total activity (-26%) and content (-14%). Also the foliar chlorophyll (-7.5%) and soluble protein content (-11%) declined significantly and the N concentration in the whole-shoot was reduced by 23%. These changes along with remarkably increased aboveground biomass (28%) demonstrate that the increased growth rates accompanying elevated [CO 2] were not matched by increased N acquisition and N assimilation, leading to a dilution of shoot N. The obtained results are discussed in relation to uncertainties associated with up-scaling of wheat yield responses to elevated [CO 2]. It is concluded that current predictions of [CO 2]-stimulated yield increases may be overstated. Key targets for future plant breeding programs are to select new wheat genotypes which have higher sink capacity for photosynthetic products and are capable of increasing nitrogen uptake under elevated [CO 2].
  • Authors:
    • Albrecht, S. L.
    • Douglas, C. L., Jr.
    • Reardon, C. L.
    • McCool, D. K.
    • Williams, J. D.
    • Rickman, R. W.
  • Source: Journal of Soil and Water Conservation
  • Volume: 68
  • Issue: 5
  • Year: 2013
  • Summary: Roots, cereal crowns, and stems growing beneath the soil surface provide important resistance to soil erosion. Understanding the amount and distribution of this material in the soil profile could provide insight into resistance to soil erosion by water and improve the performance of soil erosion models, such as the revised universal soil loss equation (RUSLE) and the water erosion prediction project (WEPP). Erosion models use built-in or external crop growth models to populate crop yield and live aboveground and associated belowground biomass databases. We examined two data sets from the dryland small grain production region in the Pacific Northwest of the United States to determine root:shoot ratios, the vertical distribution of root and attached belowground biomass, and incorporated residue from previously grown crops. Data were collected in 1993, 1994, 1995, and 2000 from short-term no-till and conventional tillage experiments conducted near Pendleton, Oregon, and Pullman,Washington, and in 1999 and 2000 from long-term experiments representative of farming practices near Pendleton, Oregon. The crops sampled in the short-term data set included soft white winter and spring wheat (Triticum aestivum L.;WW and SW, respectively), spring peas (Pisum sativum L.; SP), and winter canola (Brassica napus L.;WC). Crops sampled in the long-term study included WW SW, and SP. Data were collected at harvest in both data sets and during three phenologic stages in each of the crops in the short-term data set. Soil samples were collected to a depth of 60 cm (23.6 in) in the short-term and 30 cm (11.9 in) in the long-term experiments. In both sets of measurements, we found greater than 70% of root mass is in the top 10 cm (3.9 in) of the soil profile with the exception of SP, which had 70% of root mass in the top 15 cm (5.9 in) of the soil profile.WC produced significantly more biomass near the soil surface than WW SW, or SP Root-to-shoot biomass ratios, in mature wheat ranged from 0.13 to 0.17 in the top 30 cm (11.9 in) of the soil profile, substantially lower than values suggested for use in WEPP (0.25). In the long-term experiments, soil of the conventionally tilled continuous winter wheat (CWW) plots contained significantly greater biomass than soil of conventionally tilled winter wheat/fallow (CR) and no-till winter wheat/fallow (NT) treatments. There was no significant difference between CWW and conventionally tilled winter wheat/spring pea (WP); however, CWW returned more residue to the soil than WP because SP produced less residue and these residues were incorporated with a field cultivator rather than a moldboard plow. More accurate representation of root development, particularly in winter crops, could improve RUSLE and WEPP performance in the Pacific Northwest where winter conditions have proven difficult to model.
  • Authors:
    • Deng, J.
    • Zhou, Z. X.
    • Yao, Z. S.
    • Cui, F.
    • Zheng, X. H.
    • Yan, G. X.
    • Xu, Y.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 178
  • Year: 2013
  • Summary: Given the common problem of fertilizer overuse, agronomists are calling for a reduction of the high nitrogen dose by 1/3. We carried out a field experiment over two full winter wheat-summer maize rotations in the North China Plain (NCP) to determine whether this degree of nitrogen reduction will significantly reduce the emissions of nitrous oxide (N 2O) and nitric oxide (NO). Three treatments were investigated in the field trial: a control with no nitrogen application, the conventional practice with nitrogen over-application and the optimal practice with a reduced dose of nitrogen by 1/3. Our observations across all treatments over the experimental period reveal significant correlations of the fluxes of either gas with soil temperature and moisture as well as the concentrations of soil ammonium, nitrate and dissolvable organic carbon. There were strong correlations within the functions of the dual Arrhenius and Michaelis-Menten kinetics, giving apparent activation energy values of 40-97 and 59-92 kJ mol -1 for N 2O and NO fluxes, respectively. Our results provide annual direct emission factors of 0.48-0.96% for N 2O and 0.15-0.47% for NO and demonstrate a significant correlation between N 2O emission induced by fertilization and fertilizer nitrogen use efficiency (NUE). The correlation indicates a significant potential of N 2O mitigation via enhancing NUEs. A reduction in the nitrogen dose did not obviously mitigate either the annual NO emission in both rotations or the annual N 2O emission in the second one. However, nitrogen reduction significantly decreased the annual total N 2O emission by 38% during the first rotation. These inconsistencies in the responses of N 2O emission to the reduced nitrogen dose can be attributed to improper fertilization practices, such as broadcasting urea prior to heavy rainfalls or irrigation events during the maize season, which implies a need for further fertilization practice options/techniques in addition to the reduction of nitrogen doses.