- Authors:
- Pringle, H. C.,III
- Martin, S. W.
- Source: Journal of Cotton Science
- Volume: 7
- Issue: 4
- Year: 2003
- Summary: Deep tillage at a 45 angle has been a recommended practice since the mid-1970s on most Mississippi Delta cotton soils. This practice disrupts hard pans and allows deeper wetting of the soil profile with winter rainfall. The newest deep tillage "subsoiler" designs (Paratill, low-till parabolic) have the shank extending through the soil at an angle, thereby reducing soil surface disturbance and allowing the subsoiler to run under the row in the direction of the row, without the shank passing directly through the drill. Both centre pivot and furrow irrigation of cotton has expanded since the early 1980s. With intermittent rainfall, irrigation is supplemental and represents a type of insurance against yield uncertainty during extended periods of water deficit. Field experiments were conducted at Stoneville, Mississippi, USA, during 1994-2001, to determine the long-term effects of sprinkler irrigation and in-row subsoil tillage on cotton yield and economic return of cotton cultivars DES119 (1994-95), SG125 (1996-99) and SG747 (2000-01) on silt loam soil from 1994 to 2001. In-row subsoil tillage was performed with a low-till parabolic subsoiler and irrigation was applied with an overhead lateral-move sprinkler irrigation system. Production costs were calculated for direct costs and total specified costs excluding land rent, general farm overheads and returns to management. Average net returns were calculated as the difference between income at the cotton loan rate of $1.15 per kg of lint and total specified costs. Returns were maximized with either the irrigated, non-subsoiled or the non-irrigated, subsoiled environments. Lower returns occurred in the irrigated, subsoiled environment due to the higher costs and lack of yield increase.
- Authors:
- Jones, R. H.
- Leonard, B. R.
- Gore, J.
- Source: Environmental Entomology
- Volume: 32
- Issue: 1
- Year: 2003
- Summary: Field and laboratory studies evaluated the influence of selected crop hosts on Helicoverpa zea population dynamics in relation to genetically engineered Bt (Bollgard) and non-Bt cottons. Host specific H. zea colonies were initiated with a colony originally collected from sweetcorn. The colony was allowed to complete one generation on meridic diet then split into cohorts and allowed to complete one generation on field maize, grain sorghum, soyabean, cotton, or meridic diet in individual 29.5 ml plastic cups. During the first part of the study, larval developmental times, pupal weights, and survival were measured. H. zea survival was higher on meridic diet and grain sorghum than on soyabean and cotton. The development of H. zea larvae was faster on field maize than the other larval diets. Also, H. zea required a longer period of time to complete development on cotton than on the other hosts. Pupal weights were higher on meridic diet than the plant hosts. Pupal weights of H. zea that completed larval stadia on cotton were lower than on the other larval diets. Neonates (F 1) from each of the host specific colonies (200 per colony) were exposed to Bt and non-Bt cottons. Mortality of second generation H. zea on non-Bt and Bt cottons was measured at 96 h. H. zea larvae from the cotton colony had higher mortality on non-Bt cotton than the other host specific colonies except the grain sorghum colony. On Bt cotton, larvae from the maize colony had a higher level of mortality than larvae from the soyabean and grain sorghum colonies. These data provide valuable information for evaluating the contribution of cultivated hosts as additional, alternative refugia in Bt-cotton resistance management plans.
- Authors:
- Source: Update of research in progress at the Tamworth Agricultural Institute 2002
- Year: 2003
- Summary: Crop growth rate and weed competition were studied in New South Wales, Australia during 2002 using reflectance sensors. Seeds of wheat cv. Sunstate, chickpea cv. Howzat, faba bean cv. Fiord and rape cv. Oscar were sown at 40, 70, 100 and 3 kg/ha, respectively. Two reflectance sensors mounted on a small tractor were used to collect data across each plot every two weeks (45-129 days after sowing). Wheat recorded the greatest biomass, yield and water consumption, whereas chickpea recorded the highest harvest index and lowest water consumption. The rate of crop development was greatest in wheat and lowest in chickpea. The number of days required to produce 1000 kg/ha of shoot dry matter was 92, 100, 102 and 11 days after sowing for wheat, faba bean, rape and chickpea, respectively. Reflectance measurements were also used to evaluate the potential of wheat, triticale and barley as 'mimic weeds' against wild oat [ Avena fatua] in chickpea. Reflectance estimates were made at 51, 62, 84, 100 and 120 days after sowing. The 'mimic weeds' established faster than wild oat. The density of wild oat was lower than that of the mimic weeds, although none of the weeds achieved the target density of 81 weeds/m 2. The similar linear relationships with regard to the effects of weed biomass on crop yield for wild oat and 'mimic weeds' indicated that the latter can be used in weed studies instead of the actual weed. At low densities, wheat and barley were the most competitive. Triticale and wild oat exhibited similar competitive ability.
- Authors:
- Featherstone, A. M.
- Langemeier, M. R.
- Abdulkadri, A. O.
- Source: Applied Economics
- Volume: 35
- Issue: 7
- Year: 2003
- Summary: The risk attitudes of dryland wheat, irrigated maize, and dairy producers in Kansas, USA, are examined using the nonlinear mean-standard deviation approach. Observations on farm characteristics, obtained from 1993-97, and the statewide market year average prices for wheat and maize from 1950-97, are used. Results of analyses indicated that dryland wheat and dairy producers are characterized by increasing absolute and increasing relative risk aversion while irrigated maize producers are characterized by constant absolute and increasing relative risk aversion. Both crop enterprises exhibited constant returns to scale technology while the dairy enterprise exhibited decreasing returns to scale. Gross farm income was significant and positively related to relative risk aversion.
- Authors:
- Lokaj, G. R. W.
- Majek, B. A.
- Belding, R. D.
- Hammerstedt, J.
- Ayeni, A. O.
- Source: HortTechnology
- Volume: 13
- Issue: 2
- Year: 2003
- Summary: Peach ( Prunus persica cv. Candor) trees were established and grown from 1996 to 1999 at the Rutgers Agricultural Research and Extension Center, Bridgeton, New Jersey, USA, to compare their performance under four methods of orchard floor preparation: flat no-till, flat cultivated, mound unmulched, and mound mulched orchard floors. The experimental site was flat and the soil was a well-drained Aura gravelly sandy loam (61% sand, 31% silt and 8% clay) with a pH of 6.5, cation exchange capacity of 5.7, and organic matter content of 2.0%. Soil moisture holding capacity and gas exchange capacity determine the efficacy of mounding in peach orchards. Under these conditions, the method of orchard floor preparation had no effect on peach tree trunk cross-sectional area, fruit number per tree, fruit size and yield. Thus, without irrigation, there was no advantage to the early performance of peach trees associated with orchard floor mounding on Aura gravelly sandy loam when situated on a flat terrain.
- Authors:
- Source: Soil Science Society of America Journal
- Volume: 66
- Issue: 6
- Year: 2002
- Summary: Changes agricultural management can potentially increase the accumulation rate of soil organic C (SOC), thereby sequestering CO2 from the atmosphere. This study was conducted to quantify potential soil C sequestration rates for different crops in response to decreasing tillage intensity or enhancing rotation complexity, and to estimate the duration of time over which sequestration may occur. Analyses of C sequestration rates were completed using a global database of 67 long-term agricultural experiments, consisting of 276 paired treatments. Results indicate, on average, that a change from conventional tillage (CT) to no-till (NT) can sequester 57 +/- 14 g C m(-2) yr(-1), excluding wheat (Triticum aestivum L.)-fallow systems which may not result in SOC accumulation with a change from CT to NT. Enhancing rotation complexity can sequester an average 20 +/- 12 g C m(-2) yr(-1), excluding a change from continuous corn (Zea mays L.) to corn-soybean (Glycine mar L.) which may not result in a significant accumulation of SOC. Carbon sequestration rates, with a change from CT to NT, can be expected to peak in 5 to 10 yr with SOC reaching a new equilibrium in 15 to 20 yr. Following initiation of an enhancement in rotation complexity, SOC may reach a new equilibrium in approximately 40 to 60 yr. Carbon sequestration rates, estimated for a number of individual crops and crop rotations in this study, can be used in spatial modeling analyses to more accurately predict regional, national, and global C sequestration potentials.
- Authors:
- Source: Biomass and Bioenergy
- Volume: 22
- Issue: 5
- Year: 2002
- Summary: The focus of this study was to develop a methodology to estimate "hectare-weighted", county-level, corn stover and spring and winter wheat straw removable residue quantities in the USA for 1995-1997 in 37 states (north-south line from North Dakota to Texas and all states east) such that tolerable rainfall and wind soil loss limits were not exceeded.
- Authors:
- Lukina, E. V.
- Thomason, W. E.
- Freeman, K. W.
- Mullen, R. W.
- Stone, M. L.
- Johnson, G. V.
- Solie, J. B.
- Raun, W. R.
- Source: Agronomy Journal
- Volume: 94
- Issue: 4
- Year: 2002
- Summary: In 2001, N fertilizer prices nearly doubled as a result of increased natural gas prices. This was further troubling when considering that the world N use efficiency (NUE) in cereal grain production averages only 33%. Methods to improve NUE in winter wheat (Triticum aestivum L.) have not included high spatial-resolution management based on sensed plant growth properties nor on midseason prediction of grain yield. Our objective was to determine the validity of using in-season estimates of grain yield (INSEY) and a response index (RI) to modulate N at 1-m(2) spatial resolution. Four winter wheat field experiments were conducted that evaluated prescribed midseason N applications compared with uniform rates that simulated farmer practices. Our methods recognize that each 1-m(2) area in wheat fields needs to be sensed and managed independently and that the need for fertilizer N is temporally dependent. Averaged over locations, NUE was improved by >15% when N fertilization was based on optically sensed INSEY, determined for each 1-m(2) area, and a RI compared with traditional practices at uniform N rates.
- Authors:
- Whitehead, W. F.
- Singh, B. P.
- Sainju, U. M.
- Source: Soil & Tillage Research
- Volume: 63
- Issue: 3-4
- Year: 2002
- Summary: Maintaining and/or conserving organic carbon (C) and nitrogen (N) concentrations in the soil using management practices can improve its fertility and productivity and help to reduce global warming by sequestration of atmospheric CO2 and N2. We examined the influence of 6 years of tillage (no-till, NT; chisel plowing, CP; and moldboard plowing, MP), cover crop (hairy vetch (Vicia villosa Roth.) vs. winter weeds), and N fertilization (0, 90, and 180 kg N ha-1) on soil organic C and N concentrations in a Norfolk sandy loam (fine-loamy, siliceous, thermic, Typic Kandiudults) under tomato (Lycopersicon esculentum Mill.) and silage corn (Zea mays L.). In a second experiment, we compared the effects of 7 years of non-legume (rye (Secale cereale L.)) and legume (hairy vetch and crimson clover (Trifolium incarnatum L.)) cover crops and N fertilization (HN (90 kg N ha-1 for tomato and 80 kg N ha-1 for eggplant)) and FN (180 kg N ha-1 for tomato and 160 kg N ha-1 for eggplant)) on soil organic C and N in a Greenville fine sandy loam (fine-loamy, kaolinitic, thermic, Rhodic Kandiudults) under tomato and eggplant (Solanum melogena L.). Both experiments were conducted from 1994 to 2000 in Fort Valley, GA. Carbon concentration in cover crops ranged from 704 kg ha-1 in hairy vetch to 3704 kg ha-1 in rye in 1999 and N concentration ranged from 77 kg ha-1 in rye in 1996 to 299 kg ha-1 in crimson clover in 1997. With or without N fertilization, concentrations of soil organic C and N were greater in NT with hairy vetch than in MP with or without hairy vetch (23.5-24.9 vs. 19.9-21.4 Mg ha-1 and 1.92-2.05 vs. 1.58-1.76 Mg ha-1, respectively). Concentrations of organic C and N were also greater with rye, hairy vetch, crimson clover, and FN than with the control without a cover crop or N fertilization (17.5-18.4 vs. 16.5 Mg ha-1 and 1.33-1.43 vs. 1.31 Mg ha-1, respectively). From 1994 to 1999, concentrations of soil organic C and N decreased by 8-16% in NT and 15-25% in CP and MP. From 1994 to 2000, concentrations of organic C and N decreased by 1% with hairy vetch and crimson clover, 2-6% with HN and FN, and 6-18% with the control. With rye, organic C and N increased by 3-4%. Soil organic C and N concentrations can be conserved and/or maintained by reducing their loss through mineralization and erosion, and by sequestering atmospheric CO2 and N2 in the soil using NT with cover crops and N fertilization. These changes in soil management improved soil quality and productivity. Non-legume (rye) was better than legumes (hairy vetch and crimson clover) and N fertilization in increasing concentrations of soil organic C and N.
- Authors:
- Albrecht, A.
- Sa, J. C. D.
- Ogle, S. M.
- Denef, K.
- Feller, C.
- Six, J.
- Source: Agronomie
- Volume: 22
- Issue: 7
- Year: 2002
- Summary: The long-term stabilization of soil organic matter (SOM) in tropical and temperate regions is mediated by soil biota (e. g. fungi, bacteria, roots and earthworms), soil structure (e. g. aggregation) and their interactions. On average, soil C turnover was twice as fast in tropical compared with temperate regions, but no major differences were observed in SOM quality between the two regions. Probably due to the soil mineralogy dominated by 1:1 clay minerals and oxides in tropical regions, we found a higher aggregate stability, but a lower correlation between C contents and aggregate stability in tropical soils. In addition, a smaller amount of C associated with clay and silt particles was observed in tropical versus temperate soils. In both tropical and temperate soils, a general increase in C levels (approximate to 325 +/- 113 kg C.ha(-1).yr(-1)) was observed under no-tillage compared with conventional tillage. On average, in temperate soils under no-tillage, compared with conventional tillage, CH4 uptake (approximate to0.42 +/- 0.10 kg C-CH4.ha(-1) yr(-1)) increased and N2O emissions increased (approximate to 1.95 +/- 0.45 kg N-N2O.ha(-1).yr(-1)). These increased N2O emissions lead to a negative global warming potential when expressed on a CO2 equivalent basis.