• Authors:
    • Dobermann, A.
    • Walters, D. T.
    • Binder, D. L.
    • Haddix, M. L.
    • Adviento-Borbe, M. A. A.
  • Source: Global Change Biology
  • Volume: 13
  • Issue: 9
  • Year: 2007
  • Summary: Crop intensification is often thought to increase greenhouse gas (GHG) emissions, but studies in which crop management is optimized to exploit crop yield potential are rare. We conducted a field study in eastern Nebraska, USA to quantify GHG emissions, changes in soil organic carbon (SOC) and the net global warming potential (GWP) in four irrigated systems: continuous maize with recommended best management practices (CC-rec) or intensive management (CC-int) and maize-soybean rotation with recommended (CS-rec) or intensive management (CS-int). Grain yields of maize and soybean were generally within 80-100% of the estimated site yield potential. Large soil surface carbon dioxide (CO2) fluxes were mostly associated with rapid crop growth, high temperature and high soil water content. Within each crop rotation, soil CO2 efflux under intensive management was not consistently higher than with recommended management. Owing to differences in residue inputs, SOC increased in the two continuous maize systems, but decreased in CS-rec or remained unchanged in CS-int. N2O emission peaks were mainly associated with high temperature and high soil water content resulting from rainfall or irrigation events, but less clearly related to soil NO3-N levels. N2O fluxes in intensively managed systems were only occasionally greater than those measured in the CC-rec and CS-rec systems. Fertilizer-induced N2O emissions ranged from 1.9% to 3.5% in 2003, from 0.8% to 1.5% in 2004 and from 0.4% to 0.5% in 2005, with no consistent differences among the four systems. All four cropping systems where net sources of GHG. However, due to increased soil C sequestration continuous maize systems had lower GWP than maize-soybean systems and intensive management did not cause a significant increase in GWP. Converting maize grain to ethanol in the two continuous maize systems resulted in a net reduction in life cycle GHG emissions of maize ethanol relative to petrol-based gasoline by 33-38%. Our study provided evidence that net GHG emissions from agricultural systems can be kept low when management is optimized toward better exploitation of the yield potential. Major components for this included (i) choosing the right combination of adopted varieties, planting date and plant population to maximize crop biomass productivity, (ii) tactical water and nitrogen (N) management decisions that contributed to high N use efficiency and avoided extreme N2O emissions, and (iii) a deep tillage and residue management approach that favored the build-up of soil organic matter from large amounts of crop residues returned.
  • Authors:
    • Thakare, R.
    • Gupta, V. R.
  • Source: Indian Journal of Agricultural Research
  • Volume: 41
  • Issue: 4
  • Year: 2007
  • Summary: Effect of irrigated and rainfed cropping systems on carbon and nitrogen mineralization was studied. Maximum C and N mineralization observed under irrigated cropping systems than rainfed. Sorghum-chickpea-groundnut showed highest mineralization under irrigated condition. While monocropping and intercropping with legumes enhances the rate of mineralization under rainfed situation. Mineralization was found to be highest during grand growth period of crops. Application of integrated nutrient supply increased C and N mineralization as compared to their individual application. The FYM+wheat straw+green manuring application augmented the mineralization under soybean-wheat crop sequence.
  • Authors:
    • Kahlown, M. A.
    • Azam, M.
    • Kemper, W. D.
  • Source: Journal of Soil and Water Conservation
  • Volume: 61
  • Issue: 1
  • Year: 2006
  • Summary: Conventional management practices for the rice-wheat rotation in Pakistan's Punjab have failed to improve crop yield, increase water and fertilizer use efficiencies, and decrease production costs enough to meet an ever-increasing food demand. New technologies such as no-till, laser leveling, and bed and furrow irrigation are being rapidly adopted by the farming community, but without adequate scientific information. Therefore, those practices were evaluated on 71 farms within four representative sites. Land preparation/sowing costs, water savings, use of fertilizers, soil salinity, and crop yield were evaluated. Land preparation and sowing cost on no-till fields was significantly less than on tilled fields. Highest yields were obtained on laser-leveled fields, followed by no-till, bed and furrow fields. Water and nitrogen use efficiencies were much higher on fields with bed and furrow irrigation as compared to the conventional fields. Although the new technologies were economically feasible, we conclude that no-till was the best option for the farmers.
  • Authors:
    • Klocke, N. L.
    • Schneekloth, J. P.
    • Davison, D. R.
    • Payero, J. O.
  • Source: Irrigation Science
  • Volume: 24
  • Issue: 4
  • Year: 2006
  • Summary: Many farmers in West Central Nebraska have limited irrigation water supplies, and need to produce crops with less water. This study evaluated the impact of four water management strategies on grain yield of surface-irrigated corn ( Zea mays L.) at North Platte, Nebraska. Treatments included: (1) no irrigation (DRYLAND), (2) one irrigation prior to tassel formation (EARLY), (3) one irrigation during the silk stage (LATE), and (4) irrigation following farmer's practices (FARMER). The study included three wet years (1992, 1993, and 1996) and 2 years with average annual rainfall for the area (1994 and 1995). Significant yield differences among treatments, and a yield response to irrigation, were only observed during the 2 years with average rainfall. During all years, the FARMER treatment was over-irrigated and resulted in considerable water losses by runoff and deep percolation. Grain yield response to irrigation during the three wet years was insignificant among the treatments, but significant during the dry years. The results of this study suggest that inducing stress is not a good strategy for increasing crop water productivity (yield per unit ET d) for corn and point out the need to minimize irrigation water losses and improve irrigation scheduling.
  • Authors:
    • Payero, J. O.
    • Melvin, S. R.
    • Irmak, S.
    • Tarkalson, D.
  • Source: Agricultural Water Management
  • Volume: 84
  • Issue: 1-2
  • Year: 2006
  • Summary: Irrigation water supplies are decreasing in many areas of the US Great Plains, which is requiring many farmers to consider deficit-irrigating corn ( Zea mays L.) or growing crops like winter wheat ( Triticum aestivum L.) that require less water, but that are less profitable. The objectives of this study were to: (1) quantify the yield response of corn to deficit irrigation, and (2) determine which of several seasonal water variables correlated best to corn yield in a semiarid climate. Eight (T1-T8) and nine (T1-T9) deficit-irrigated treatments (including dryland), were compared in 2003 and 2004 in North Platte, Nebraska. The actual seasonal crop evapotranspiration (ET d) (calculated with procedures in FAO-56) for the different treatments was 37-79% in 2003 and 63-91% in 2004 compared with the seasonal crop evapotranspiration when water is not limited (ET w). Quantitative relationships between grain yield and several seasonal water variables were developed. Water variables included, irrigation ( I), total water ( Wall), rain+irrigation ( WR+I ), evaporation ( E), crop evapotranspiration (ET d), crop transpiration ( Td), and the ratios of ET d and Td to evapotranspiration and transpiration when water is not limited (ET w and Tw). Both years, yield increased linearly with seasonal irrigation, but the relationship varied from year to year. Combining data from both years, ET d had the best correlation to grain yield (yield=0.028ET d-5.04, R2=0.95), and the water variables could be ranked from higher to lower R2 when related to grain yield as: ET d ( R2=0.95) > Td ( R2=0.93) > ET d/ET w ( R2=0.90) = Td/ Tw ( R2=0.90) > Wall ( R2=0.89) > E ( R2=0.75) > WR+I ( R2=0.65) > I ( R2=0.06). Crop water productivity (CWP) (yield per unit ET d) linearly increased with ET d/ET w ( R2=0.75), which suggests that trying to increase CWP by deficit-irrigating corn is not a good strategy under the conditions of this study.
  • Authors:
    • Shivani
    • Mishra, S.
    • Singh, V.
    • Sanjeev, K.
  • Source: Indian Journal of Agricultural Sciences
  • Volume: 76
  • Issue: 9
  • Year: 2006
  • Summary: A field experiment was conducted in Bihar, India during the winter of 2002-04 to determine the effects of irrigation and tillage on the soil-water-plant relationship and productivity of maize cv. Deoki. The treatments included disc ploughing + 2 harrowing + planking (T1), 2 cultivator + planking (T2), rotavator (T3) and zero-till planter (T4), in combination with 3 irrigations during the pre-knee height of the crop (30 days after sowing (DAS)), knee height and silking stages (I1), I1 + irrigation during the milking stage (I2), irrigation during the pre-knee height, knee-height, tasseling, milking and grain filling stages (I3) and irrigation during the pre-knee height, knee height, tassel initiation, silking, milking and grain filling stages (I4). The physical properties of the soil of rotavator-tilled plots recorded higher bulk density (1.33 and 1.30 mg/m 3), soil strength (2.10 and 2.05 MPa), infiltration rate (0.420 and 0.432 cm/ha) and porosity (49.81 and 50.94%) during 2002-03 and 2003-04, respectively. Plant height (189.33 and 190.07 cm), leaf area index (2.673 and 2.728) dry matter accumulation (369.77 and 392.78 g) and relative leaf water content (94.61 and 93.36%) were highest with rotavator tilling during 2002-03 and 2003-04. Plants receiving 5-6 irrigations exhibited superior crop yield and yield attributes. Rotavator-tilled maize showed higher water expense efficiency compared to plants under different tillage systems. Rotavator tilled maize irrigated 5-6 times recorded the highest grain yield (5831 and 5960kg/ha) and net returns (Rs. 16 173 and Rs. 17 493) during 2002-03 and 2003-04, respectively.
  • Authors:
    • Bona, F. D. de
    • Bayer, C.
    • Bergamaschi, H.
    • Dieckow, J.
  • Source: REVISTA BRASILEIRA DE CIENCIA DO SOLO
  • Volume: 30
  • Issue: 5
  • Year: 2006
  • Summary: The effect of irrigation on soil C stocks is a result of the balance between the effect of this practice on C input through crop residues and of C losses through microbial decomposition of soil organic matter (SOM). This study assessed the influence of sprinkler irrigation on SOM dynamics and on the total C stocks in a subtropical Acrisol under no-tillage (NT) and conventional tillage (CT) in a long-term experiment (8 years) in Universidade Federal do Rio Grande do Sul, RS, Brazil. Irrigation increased the C addition (about 8 kg C ha -1 yr -1 per mm precipitation) in both tillage systems, but this was not enough to increase the soil C stocks (0-20.0 cm) because irrigation also increased the decomposition rate of SOM by 19% in the CT soil and by 15% in NT soil. In the top layers (0-2.5 and 2.5-5.0 cm), the C concentration was higher in the NT than in CT soil, while the opposite trend was observed in the deepest layer (10.0-20.0 cm). Thus, the total C stocks in the whole 0-20.0 cm layer did not differ between tillage systems. The oat residue decomposition rate in NT soil increased with irrigation, which corroborates the higher SOM decomposition rates estimated for the irrigated soil. Based on these results, it becomes clear that the establishment of a high input cropping system able to counterbalance the higher SOM decomposition rates is a crucial point in the maintenance or improvement of soil C stocks in irrigated tropical and subtropical croplands.
  • Authors:
    • Gill, M.
    • Sarlach, R.
  • Source: Environment and Ecology
  • Volume: 24
  • Issue: 1
  • Year: 2006
  • Summary: The kandi region comprising 0.5 m ha (about 9.5%) of Punjab, India, is characterized undulated topography, light soil texture, heavy run off and soil erosion losses, poor moisture retentivity and devoid of easily exploitable underground water sources, and is therefore highly dependent upon seasonal south-west monsoon (July-September). It is coupled with poor infrastructure of roads and marketing, illiteracy, heavy cattle and human population pressure and agriculture adopted as subsidiary occupation. About 25-40% of the monsoon rains is lost as run off. The soils are non-saline, organic carbon averages 0.24% in loamy sand and 0.30 or more in sandy loam soils. The corresponding values of moisture retention at 1/3 bar or field capacity range from 8.1 to 15.8% and at 15 bar (permanent wilting point) from 3.7 to 4.8% in 0-180 cm soil layer of loamy sand soil and 16.2 to 21.5% and 3.7 to 7.6% respectively in sandy loam soil. In situ soil moisture conservation with the minor leveling, bunding and installation of suitable water structure helped to increase the yield of wheat [ Triticum aestivum] + gram [ Vigna mungo] by 57% and pearl millet by 25%. In light soil, green manuring during kharif gave an edge of 0.5 q/ha over the fallow fields on account of more rain water conservation and addition of green matter in soil. Mulching in standing maize [ Zea maize] in kharif helped to conserve the moisture in seed zone (0-15 cm) layer and ensured germination of succeeding wheat crop. Using the stored water in ponds during rainy season and its use as light irrigation (5 cm) at the initial moisture stress or as life saving irrigation, resulted in the better establishment of crops and increased the yield by 669 kg/ha over the controlled un-irrigated plots. Amongst the various crops, management practices conserving the soil moisture during kharif season and taking winter season crop were found promising technologies. Raya grown as an inter-rowcrop at 2.0 to 2.5 meter interval gave 2.5 q/ha seed yield. Application of fertilizer under dry land conditions seemed to be a prerequisite. It improved the above-, and below-, ground biomass and helped extend the root system to exploit water from deeper layer of soils and enabled the crop sustain the drought better and resulted in 50-70% grain yield increases in combination with fertilizer application. Under such an approach, fertilizer schedule for wheat was established at 80-40-20; N-P 2O 5-K 2O kg/ha in medium to heavy soil; and 40-20-10; N-P 2O 5-K 2O kg/ha for wheat or wheat+gram for light soils while the fodder ( kharif) and raya required just about 50 kg. N/ha.
  • Authors:
    • Halvorson, A. D.
    • Reule, C. A.
  • Source: Agronomy Journal
  • Volume: 98
  • Issue: 5
  • Year: 2006
  • Summary: Irrigated, no-till (NT) production systems can potentially reduce soil erosion, fossil fuel consumption, and greenhouse gas emissions compared with conventional till (CT) systems. Including a legume in the rotation may also reduce N fertilizer requirements. Nitrogen fertilization (6 N rates) effects on irrigated, corn (Zea mays L.) and soybean [Glycine mar (L.) Merr.] yields in a corn-soybean rotation were evaluated for 5 yr on a clay loam soil to determine the viability of an irrigated NT system and N needs for optimum crop yield. Corn grain yields were significantly increased by N fertilization each of 3 yr in the rotation, but soybean grain yields (2 yr) did not respond to N fertilization, averaging 2.79 Mg ha(-1). Three year average corn grain yields were near maximum with an available N (AN) (soil + fertilizer + irrigation water N) level of 257 kg N ha(-1). Nitrogen use efficiency (NUE) by corn and soybean, based on grain N removal, decreased with increasing AN level and ranged from 155 to 46 and 88 to 18 kg grain kg(-1) AN for the low and high N treatments for corn and soybean, respectively. Estimated total N required to produce one Mg grain at maximum yield averaged 20 kg N for corn and 54 kg N for soybean. Corn residue increased with increasing N rate, but soybean residue was constant across N rates. Excellent irrigated, NT corn yields were obtained in this corn-soybean rotation for northern Colorado, but soybean yields were only marginally acceptable. Short soybean plant height (30-40 cm) and shattering made combine harvest difficult resulting in significant grain loss. Improved soybean cultivars are needed for this area to make a corn-soybean rotation a viable production system.
  • Authors:
    • Waddell, J.
    • Caesar-Tonthat, T.
    • Lenssen, A.
    • Sainju, U. M.
  • Source: Soil Science Society of America Journal
  • Volume: 70
  • Issue: 2
  • Year: 2006
  • Summary: Sustainable management practices are needed to enhance soil productivity in degraded dryland soils in the northern Great Plains. We examined the effects of two tillage practices [conventional till (CT) and no-till (NT)], five crop rotations [continuous spring wheat (Triticum aestivum L.) (CW), spring wheat-fallow (W-F), spring wheat-lentil (Lens culinaris Medic.) (W-L), spring wheat-spring wheat-fallow (W-W-F), and spring wheat-pea (Pisum sativum L.)-fallow (W-P-F)], and a Conservation Reserve Program (CRP) on plant biomass returned to the soil, residue C and N, and soil organic C (SOC), soil total N (STN), and particulate organic C and N (POC and PON) at the 0- to 20-cm depth. A field experiment was conducted in a mixture of Scobey clay loam (fine, smectitic, frigid Aridic Argiustolls) and Kevin clay loam (fine-loamy, mixed, superactive, frigid Aridic Argiustolls) from 1998 to 2003 near Havre, MT. Mean annualized plant biomass returned to the soil from 1998 to 2003 was greater in W-F (2.02 Mg ha-1) than in W-L and W-W-F, regardless of tillage. In 2004, residue cover was greater in CW (60%) than in other rotations, except in W-W-F. Residue amount and C and N contents were greater in NT with CW (2.47 Mg ha-1 and 963 and 22 kg ha-1, respectively) than in NT with W-L and CT with other crop rotations. The POC at 0 to 5 cm was greater in W-W-F and W-P-F (2.1-2.2 Mg ha-1) than in W-L. Similarly, STN at 5 to 20 cm was greater in CT with W-L (2.21 Mg ha-1) than in other treatments, except in NT with W-W-F. Reduced tillage and increased cropping intensity, such as NT with CW and W-L, conserved C and N in dryland soils and crop residue better than the traditional practice, CT with W-F, and their contents were similar to or better than in CRP planting.