• Authors:
    • Lenssen, A. W.
    • Johnson, G. D.
    • Carlson, G. R.
  • Source: Field Crops Research
  • Volume: 100
  • Issue: 1
  • Year: 2007
  • Summary: Available water is typically the biggest constraint to spring wheat production in the northern Great Plains of the USA. The most common rotation for spring wheat is with summer fallow, which is used to accrue additional soil moisture. Tillage during fallow periods controls weeds, which otherwise would use substantial amounts of water, decreasing the efficiency of fallow. Chemical fallow and zero tillage systems improve soil water conservation, allowing for increased cropping intensity. We conducted a field trial from 1998 through 2003 comparing productivity and water use of crops in nine rotations under two tillage systems, conventional and no-till. All rotations included spring wheat, two rotations included field pea, while lentil, chickpea, yellow mustard, sunflower, and safflower were present in single rotations with wheat. Growing season precipitation was below average most years, resulting in substantial drought stress to crops not following fallow. Preplant soil water, water use, and spring wheat yields were generally greater following summer fallow than wheat recropped after wheat or alternate crops. Water use and yield of wheat following summer fallow was greater than for chickpea or yellow mustard, the only other crops in the trial that followed summer fallow. Field pea performed best of all alternate crops, providing yields comparable to those of recropped spring wheat. Chickpea, lentil, yellow mustard, safflower, and sunflower did not perform well and were not adapted to this region, at least during periods of below average precipitation. Following summer fallow, and despite drought conditions, zero tillage often provided greater amounts of soil water at planting compared to conventional tillage.
  • Authors:
    • Lenssen, A. W.
    • Waddell, J. T.
    • Johnson, G. D.
    • Carlson, G. R.
  • Source: Soil & Tillage Research
  • Volume: 94
  • Issue: 2
  • Year: 2007
  • Summary: Improved nitrogen use efficiency would be beneficial to agroccosystem sustainability in the northern Great Plains of the USA. The most common rotation in the northern Great Plains is fallow-spring wheat. Tillage during fallow periods controls weeds, which other-wise would use substantial amounts of water and available nitrogen, decreasing the efficiency of fallow. Chemical fallow and zero tillage systems improve soil water conservation, and may improve nitrogen availability to subsequent crops. We conducted a field trial from 1998 through 2003 comparing nitrogen uptake and nitrogen use efficiency of crops in nine rotations under two tillage systems, conventional and no-till. All rotations included spring wheat, two rotations included field pea, while lentil, chickpea, yellow mustard, sunflower, and safflower were present in single rotations with wheat. Growing season precipitation was below average in 3 of 4 years, resulting in substantial drought stress to crops not following fallow. In general, rotation had a greater influence on spring wheat nitrogen accumulation and use efficiency than did tillage system. Spring wheat following fallow had substantially higher N accumulation in seed and biomass, N harvest index, and superior nitrogen use efficiency than wheat following pea, lentil, chickpea, yellow mustard, or wheat. Preplant nitrate-N varied widely among years and rotations, but overall, conventional tillage resulted in 9 kg ha(-1) more nitrate-N (060 cm) for spring wheat than did zero tillage. However, zero tillage spring wheat averaged 11 kg ha(-1) more N in biomass than wheat in conventional tillage. Nitrogen accumulation in pea seed, 45 kg ha(-1) was superior to that of all alternate crops and spring wheat, 17 and 23 kg ha(-1), respectively. Chickpea, lentil, yellow mustard, safflower, and sunflower did not perform well and were not adapted to this region during periods of below average precipitation. During periods of drought, field pea and wheat following fallow had greater nitrogen use efficiency than recropped wheat or other pulse and oilseed crops.
  • Authors:
    • Zhang,X. C.
    • Liu,W. Z.
  • Source: Field Crops Research
  • Volume: 100
  • Issue: 2-3
  • Year: 2007
  • Summary: Matching fertilizer rates with available water supplies in water-scarce environments remains a major challenge for improving water use efficiency and crop yield. The objectives are to (i) develop a new approach to characterizing interrelations of yield ( Y), evapotranspiration (ET), water use efficiency (WUE), and soil fertility using an elasticity index, and (ii) to further derive optimal-coupling domains of water and fertilizer inputs using maize data of 1997 and 1998, as an example. The experiment was an incomplete factorial design with two factors (water supply and fertilizer input) with five levels each, and had a total of 13 treatments with three replicates each. A maize cultivar (Zhongdan 2, Zea mays L.) was grown in a loessial silt loam in the hilly region of the Loess Plateau of China. Irrigation was hand applied at predetermined amounts as needed, and fertilizers including nitrogen, phosphate, and yard manure were applied at planting and jointing at predetermined rates. Approaches on how to use the crop-water production function and elasticity index (EI) to characterize the interrelations of Y, ET, and WUE were presented, and further extended to derive the optimal-coupling domains of water and fertilizer inputs. Yield responses to water and fertilizer inputs followed a quadratic function with a positive interactive term. When constrained by local maximum yields, the optimal-coupling domain took a half-ellipse form with the global maximum WUE and Y (or maximum ET) corresponding to the left and right end points on its long axis. As water supply increased, WUE reached its maximum before yield did. If water supply is limiting, fertilizer rates that maximize WUE rather than yield should be used; otherwise, seeking maximum yield may be desirable. For irrigation management, total water supply to maize should not exceed 550 mm in the region. Furthermore, the optimal domain can be used to determine optimal fertilizer rates for any given water supply, which may be estimated from seasonal climate forecasts in the case of dryland farming or based on available water supply for future irrigation. For a given water supply, fertilizer rates should be between the rate of reaching local maximum WUE and the rate of reaching local maximum yield.
  • Authors:
    • Sainju, U. M.
    • Caesar-TonThat, T.
    • Lenssen, A. W.
    • Evans, R. G.
    • Kolberg, R.
  • Source: Soil Science Society of America Journal
  • Volume: 71
  • Issue: 6
  • Year: 2007
  • Summary: Long-term management practices are needed to increase dryland C storage and improve soil quality. We evaluated the 21-yr effects of combinations of tillage and cropping sequences on dryland crop biomass (stems + leaves) returned to the soil, residue C, and soil C fractions at the 0- to 20-cm depth in a Dooley sandy loam (fine-loamy, mixed, frigid, Typic Argiborolls) in eastern Montana. Treatments were no-till continuous spring wheat (Triticum aestivum L.) (NTCW), spring-tilled continuous spring wheat (STCW), fall- and spring-tilled continuous spring wheat (FSTCW), fall- and spring-tilled spring wheat-barley (Hordeum vulgare L.) (1984-1999) followed by spring wheat-pea (Pisum sativum L.) (2000-2004) (FSTW-B/P), and spring-tilled spring wheat-fallow (STW-F). Carbon fractions were soil organic C (SOC), soil inorganic C (SIC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). Mean crop biomass was 53 to 66% greater in NTCW, STCW, FSTCW, and FSTW-B/P than in STW-F. Soil surface residue amount and C content in 2004 were 46 to 60% greater in NTCW and FSTCW than in STW-F As a result, soil C fractions at 0 to 20 cm were 23 to 141 % greater in all other treatments than in STW-F due to increased C input. At 0 to 5 cm, SOC, SIC, POC, and PCM were greater in NTCW than in FSTW-B/P. At 5 to 20 cm, POC was greater in NTCW than in FSTW-B/P and PCM was greater in STCW than in FSTCW. Long-term reduced tillage with continuous nonlegume cropping increased dryland crop biomass, residue and soil C storage, and soil quality by increasing microbial biomass and activities compared with a conventional system such as STW-F.
  • Authors:
    • Lenssen, A.
    • Caesar-Thonthat, T.
    • Waddell, J.
    • Sainju, U. M.
  • Source: Soil & Tillage Research
  • Volume: 93
  • Issue: 2
  • Year: 2007
  • Summary: Soil and crop management practices may alter the quantity, quality, and placement of plant residues that influence soil C and N fractions. We examined the effects of two tillage practices [conventional till (CT) and no-till (NT)] and five crop rotations [continuous spring wheat (Triticum aestivum L.) (CW), spring wheat-fallow (W-F), spring wheat-lentil (L-ens culinaris Medic.) (W-L), spring wheat-spring wheat-fallow (W-W-F), and spring wheat-pea (Pisum sativum L.)-fallow (W-P-F)] on transient land previously under 10 years of Conservation Reserve Program (CRP) planting on the amount of plant biomass (stems + leaves) returned to the soil from 1998 to 2003 and soil C and N fractions within the surface 20 cm in March 2004. A continued CRP planting was also included as another treatment for comparing soil C and N fractions. The C and N fractions included soil organic C (SOC), soil total N (STN), microbial biomass C and N (MBC and MBN), potential C and N mineralization (PCM and PNM), and NH4-N and NO3-N contents. A field experiment was conducted in a mixture of Scobey clay loam (fine-loamy, mixed, Aridic Argiborolls) and Kevin clay loam (fine, montmorillonitic, Aridic Argiborolls) in Havre, MT, USA. Plant biomass yield varied by crop rotation and year and mean annualized biomass was 45-50% higher in CW and W-F than in W-L. The SOC and PCM were not influenced by treatments. The MBC at 0-5 cm was 26% higher in W-W-F than in W-F. The STN and NO3-N at 5-20 cm and PNM at 0-5 cm were 17-1206% higher in CT with W-L than in other treatments. Similarly, MBN at 0-5 cm was higher in CT with W-L than in other treatments, except in CT with W-F and W-P-F. Reduction in the length of fallow period increased MBC and MBN but the presence of legumes, such as lentil and pea, in the crop rotation increased soil N fractions. Six years of tillage and crop rotation had minor influence on soil C and N storage between croplands and CRP planting but large differences in active soil C and N fractions.
  • Authors:
    • Young, D. L.
    • Schillinger, W. F.
    • Kennedy, A. C.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 120
  • Issue: 2-4
  • Year: 2007
  • Summary: The tillage-based winter wheat (Triticum aestivum L.)-summer fallow (WW-SF) cropping system has dominated dryland farming in the Pacific Northwest USA for 125 years. We conducted a large-scale multidisciplinary 8-year study of annual (i.e., no summer fallow) no-till cropping systems as an alternative to WW-SF. Soft white and hard white classes of winter and spring wheat, spring barley (Hordeum vulgare L.), yellow mustard (Brassica hirta Moench), and safflower (Carthamus tinctorius L.) were grown in various rotation combinations. Annual precipitation was less than the long-term average of 301 mm in 7 out of 8 years. Rhizoctonia bare patch disease caused by the fungus Rhizoctonia solani AG-8 appeared in year 3 and continued through year 8 in all no-till plots. All crops were susceptible to rhizoctonia, but bare patch area in wheat was reduced, and grain yield increased, when wheat was grown in rotation with barley every other year. Remnant downy brome (Bromus tectorum L.) weed seeds remained dormant for 6 years and longer to heavily infest recrop winter wheat. There were few quantifiable changes in soil quality due to crop rotation, but soil organic carbon (SOC) increased in the surface 0-5 cm depth with no-till during the 8 years to approach that found in undisturbed native soil. Annual no-till crop rotations experienced lower average profitability and greater income variability compared to WW-SF. Yellow mustard and safflower were not economically viable. Continuous annual cropping using no-till provides excellent protection against wind erosion and shows potential to increase soil quality, but the practice involves high economic risk compared to WW-SF. This paper provides the first comprehensive multidisciplinary report of long-term alternative annual no-till cropping systems research in the low-precipitation region of the Pacific Northwest.
  • Authors:
    • Schmidt, C. J. J.
    • Adriaanse, F. G.
    • Preez, C. C. du
  • Source: South African Journal of Plant and Soil
  • Volume: 24
  • Issue: 1
  • Year: 2007
  • Summary: The principle objective of this study was to establish P fertilizer guidelines for dryland maize on the South African Highveld according to the sufficiency concept of soil extractable P. Data sets from nine different P fertilizer trials at various localities in the Free State, Gauteng, Mpumalanga and North West provinces were used. Different P treatments were applied for all trials in order to establish differences in extractable soil P levels, which were expected to have corresponding effects on maize yield. Long-term rainfall varied from 765 mm per annum for the Dirkiesdorp trial in the east to 494 mm per annum for the Wolmaransstad trial in the west. The duration of trials varied between one and nine seasons. The clay content of the top 150 mm soil at these localities ranged between 8.4 and 47%. Extractable P threshold values with varying R 2 values were derived for all localities. These values were related to soil properties and it was shown that the degree of leaching and silt-plus-clay content were the parameters that explained most of the variation. However, it was decided only to explore relationships between threshold P values and silt-plus-clay contents in more detail. By excluding data from two localities of which the topsoil contained free lime, the R 2 values of the mentioned relationships improved substantially so that P threshold values could be derived from the silt-plus-clay content range of the other seven localities. The extractable soil P threshold concentrations based on Bray 1 for the top 150 mm soil layer, to obtain 90% relative yield varied from 33.5 mg kg -1 at 13% silt-plus-clay to 14.6 mg kg -1 at 60% silt-plus-clay. These P thresholds were much higher on the sandy soils than the value of 19 mg P kg -1 (Bray 1) for 95% relative yield according to the ARC-Grain Crops Institute (1994) guidelines over all soils. This may not necessarily imply that overall more P fertilizers should be applied, since the corresponding soil sampling procedure also measures residual P from enriched zones over rows where P fertilizer was band-placed. Research results used to establish the ARC-Grain Crops Institute (1994) guidelines excluded sampling from enriched zones over rows.
  • Authors:
    • Babu, K. S.
    • Sharma, R. K.
    • Kumar, K.
    • Sharma, A. K.
  • Source: Crop Protection
  • Volume: 26
  • Issue: 6
  • Year: 2007
  • Summary: A study was conducted to evaluate the influence of tillage systems on the incidence of Tilletia indica (Karnal bunt) in a rice-wheat system that is the most popular and prevalent crop rotation in the Indo-Gangetic Plains of India. A total of 906 samples, were drawn from the farmers' fields during the month of April during the 3 years study period. The samples collected were 365, 171, and 370 from the zero tillage (ZT), furrow irrigated raise bed system (FIRBS), and conventional till (CT) sown fields, respectively. The disease incidence, incidence index and percent-infected samples were calculated and statistically analyzed. Results showed that ZT fields had the lowest mean incidence of Karnal bunt, i.e. 9.00% infected samples in comparison to 18.10% and 16.20% under FIRBS and CT, respectively. Similarly, the average infection in infected samples was equal in FIRBS and CT, but the samples from ZT were statistically lower. KB incidence index showed a similar trend. ZT has shown a reduced incidence of KB in comparison to the raised bed (FIRBS) and CT systems. If ZT is followed for a period of a few years, it may help in reducing the effective soil inoculum and reducing the disease incidence over time.
  • Authors:
    • Shah, Z.
    • Stromberger, M.
    • Westfall, D.
  • Source: Applied Soil Ecology
  • Volume: 35
  • Issue: 1
  • Year: 2007
  • Summary: In degraded agricultural soils, organic C levels can be increased and conserved by adopting alternative management strategies such as no-tillage and increased cropping intensity. However, soil microbial community responses to increased soil organic C (SOC) may be constrained due to water limitations in semi-arid dryland agroecosystems. The purpose of this study was to assess SOC, microbial biomass C (MBC) and community ester-linked fatty acid methyl ester (EL-FAME) composition under winter wheat ( Triticum aestivum L.) in no-till systems of wheat-corn ( Zea mays L.)-fallow (WCF), wheat-wheat-corn-millet ( Panicum miliaceum L.) (WWCM), wheat-corn-millet (WCM), opportunity cropping (OPP), and perennial grass across a potential evapotranspiration gradient in eastern Colorado. Rotations of WWCM and OPP, in which crops are chosen based on available soil water at the time of planting rather than according to a predetermined rotation schedule, increased levels of SOC to those measured under perennial grass. However, MBC under OPP cropping accounted for the smallest fraction (2.0-3.6%) of SOC compared to other systems, in which MBC ranged from 2.4 to 6.3% of SOC. Microbial community structure was most divergent between OPP-cropped and perennial grass soils, whereas few differences were observed among microbial communities of the WCF, WCM, and WWCM rotations. Compared to perennial grass and other cropping systems, microbial biomass in OPP-cropped soil was low and contained less of the arbuscular mycorrhizal fungal biomarker 16:1omega5 c. Microbial stress, as indicated by the ratio of 17:0 cy to 16:1omega7 c, was greatest under OPP and WCF cropping. In contrast, soils under perennial grass contained lower ratios of bacterial:fungal EL-FAMEs and higher levels of MBC, ratios of MBC:SOC, and relative abundances of 16:1omega5 c. Across locations, SOC and moisture content increased as soil texture became finer, whereas trends in MBC and community structure followed the potential evapotranspiration gradient. Soil from the high potential evapotranspiration site contained the lowest level of MBC but greater relative amounts of 16:1omega5 c and lower ratios of stress indicator and bacterial:fungal EL-FAMEs compared to soil located at the moderate and low potential evapotranspiration sites. Indistinct microbial communities under WCF, WCM, and WWCM could be explained by EL-FAME limitations to detecting slight differences in microbial community structure or to the overwhelming response of microbial communities to environmental rather than management conditions. Further research is needed to assess potential legacy effects of long-term agricultural management that may mask microbial responses to recent management change, as well as to identify conditions that lead to high microbial community resiliency in response to management so that communities are similar under a given crop despite different preceding crops.
  • Authors:
    • Oenema, O.
    • Perdok, U. D.
    • Hoogmoed, W. B.
    • Cai, D.
    • Wang, X.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 79
  • Issue: 1
  • Year: 2007
  • Summary: The rapidly increasing population and associated quest for food and feed in China has led to increased soil cultivation and nitrogen (N) fertilizer use, and as a consequence to increased wind erosion and unbalanced crop nutrition. In the study presented here, we explored the long-term effects of various combinations of maize stover, cattle manure and nitrogen (N) and phosphorus (P) fertilizer applications on maize ( Zea mays L.) yield and nutrient and water use efficiencies under reduced tillage practices. In a companion paper, we present the effects on nutrient balances and soil fertility characteristics. The ongoing factorial field trial was conducted at Shouyang Dryland Farming Experimental Station in northern China from 1993 onwards. The incomplete, determinant-optimal design comprised 12 treatments, including a control treatment, in duplicate. Grain yields and N, P, and potassium (K) uptakes and N, P and K use efficiencies were greatly influenced by the amount of rain during the growing season (GSR), and by soil water at sowing (SWS). There were highly significant interactions between GSR and added stover and manure, expressed in complex annual variations in grain yield and N, P and K use efficiencies. Annual mean grain yields ranged from 3,000 kg ha -1 to 10,000 kg ha -1 and treatment mean yields from 4,500 kg ha -1 to 7,000 kg ha -1. Balanced combination of stover (3,000-6,000 kg), manure (1,500-6,000 kg) and N fertilizer (105 kg) gave the highest yield. Stover and manure were important for supplying K, but the effects differed greatly between years. Overall mean N recovery efficiency (NRE) ranged from 28% to 54%, depending on N source. NRE in wet years ranged from 50% to 90%. In conclusion, balanced combinations of stover, manure and NP fertilizer gave the highest yield and NRE. Reduced tillage with adding stover and manure in autumn prior to ploughing is effective in minimizing labour requirement and wind erosion. The potentials of split applications of N fertilizer, targeted to the need of the growing crop (response farming), should be explored to further increase the N use efficiency.