• Authors:
    • Roggenstein, V.
    • Fischbeck, G.
    • Dennert, J.
  • Source: Getreide Magazin
  • Issue: 3
  • Year: 2001
  • Summary: A study was initiated in 1980 in Germany on a soil with 4% humus and 18.2 mg P 20 5/100 g soil and 35.7 mg K 20/100 g soil. Crops included winter wheat, barley, rye, oats, rape, and maize. Annual soil analyses showed an unexpectedly large variation following inputs of up to 60 kg P/ha and 80 kg K/ha. The difference in P and K supply between fertilized and unfertilized plots was around 20%. However, the effect on yields was less than might have been expected. Non-application of P did not influence yield, while non-application of K resulted in 5% decrease (despite high K availability). No direct relationship was found between soil analysis and yields.
  • Authors:
    • Ayuk, E. T.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 61
  • Issue: 1-2
  • Year: 2001
  • Summary: In recent years and in some situations the status of soil organic matter (SOM) has deteriorated considerably due to long periods of continuous cultivation and limited external inputs in the form of mineral fertilizers. Deterioration of SOM varies by agro-ecological zones, by soil types and by cropping patterns. It is more intense in East Africa, followed by coastal West Africa and Southern Africa and least intensive in the Sahel and Central Africa. It is also more serious in areas under low-input agriculture irrespective of the prevailing cropping system. The major consequence of the decrease in SOM in the tropics is lower agricultural productivity with a direct negative effect on food security. While biophysical dynamics of SOM have been extensively covered in the literature, social considerations have not received similar attention. This paper examines the social, economic and policy factors associated with the management of tropical soil organic matter. Empirical data from a range of environments in Africa show that SOM improvement options yield a positive return to land as well as labour. However, there are a number of constraints. Social constraints are related to the large quantities of organic matter that are required (case of farmyard manure), the competitive uses for the material (case of crop residues), land and labour requirements, and gender-related issues. From a policy stand point, unsecured tenure rights together with price distortions and other market failures may be important constraints. Challenges for sustainable management of SOM are identified. These include management conflicts, land tenure arrangements, the divergence in goals between individuals and society, land and labour requirements, inadequate support systems for land users, profitability issues, the role of subsidies, and the absence of national action plans. A number of opportunities are identified that could enhance the improvement or maintenance of SOM. These include: exploring the need and potential role of community-based SOM management practices; development of an integrated plant nutrient management strategy involving both organic and inorganic inputs; and development of concrete national action plans. It is argued that because externalities of SOM improvement or maintenance extend beyond the farmer's fields, SOM investment may require cost sharing between individuals and the society. Policies on subsidies need to be reconsidered. Research priorities are identified that require closer collaboration between scientists from a variety of disciplines.
  • Authors:
    • Kayisoglu, B.
    • Yalcn, H.
    • Koc, F.
    • Gonulol, E.
    • Bayhan, Y.
  • Source: Farm work science facing the challenges of the XXI century. Proceedings XXIX CIOSTA-GIGR V Congress, Krakow, Poland, 25-27 June, 2001, p. 30-35
  • Volume: 10
  • Year: 2001
  • Summary: The effect of different tillage methods on silage quality in second crop maize for silage was determined in this study. For this purpose, second crop maize was planted by using the following tillage methods: (1) Direct drilling (no-till) (DRD); (2) Heavy duty disc harrow+pneumatic precision drill (DIS); (3) Plough+disc harrow+roller+pneumatic precision drill (PLO); (4) Rotary tiller+pneumatic precision drill (ROT); (5) Tillage combination+pneumatic precision drill (TIC); and (6) Irrigation+Plough+disc harrow+roller+pneumatic precision drill (conventional) (CON). After harvesting, plant samples were filled into PVC silos (with three replication for each treatment) for fermentation and kept in these silos for 75 days. Significant statistical differences were found between treatments (tillage methods) according to pH, DM (dry matter), CA (crude ash), CF (crude fibre), WSC (water soluble carbohydrate), NH 3-N 3 and LAB (lactic acid batteries). Quality parameters in all treatments remained between the desired levels. No-tillage method with DRD and minimum tillage methods with ROT and TIC can be suggested.
  • Authors:
    • Swanton, C.
    • Vyn, T. J.
    • Hooker, D. C.
    • Weersink, A.
    • Yiridoe, E. K.
  • Source: Canadian Journal of Agricultural Economics
  • Volume: 48
  • Issue: 2
  • Year: 2000
  • Summary: Conservation tillage systems have not been widely adopted on clay soils. There are few empirical studies on the production potential and economic feasibility of conservation tillage systems for corn (Zea mays L.) and soybean (Glycine max L.) production on clay soils. On some soils in some regions, crop yields and possibly profitability can be increased and yield and net farm returns risks may be reduced through the use of conservation tillage systems. Stochastic dominance efficiency criteria are used to rank net return distributions for one conventional tillage (CT) and seven conservation tillage (including five reduced tillage and two no-till) systems conducted for corn and soybean cropping systems on two clay soils located in the 3050 to 3100 Corn Heat Unit areas of Ontario. Average yields are similar under conventional tillage and reduced tillage systems, although actual corn and soybean yield response to tillage treatment is affected by drought (year). Average net returns differ among tillage treatments due to two factors. First, actual corn and soybean yields vary among tillage systems for each soil type, depending on weather (i.e., year) effects. In addition, machinery costs that are crop-specific increase costs of production and therefore reduce net returns In general, CT systems dominate both reduced tillage and no-till systems for almost all risk intervals for both clay soils, except for slightly high-risk-preferring intervals.
  • Authors:
    • Dı́az-Zorita, M.
  • Source: Soil & Tillage Research
  • Volume: 54
  • Issue: 1-2
  • Year: 2000
  • Summary: Subsoiling a compacted soil should loosen it, improve the physical conditions, and increase nutrient availability and crop yields. The aim of this work is to compare the effects of different tillage and fertility treatments in a loamy Typic Hapludoll soil, and to determine the interactions of N fertilization with several soil properties and dryland corn (Zea mays L.) productivity, The experiment, conducted in 1995 and in 1997, had a split-plot design consisting of three tillage systems (MB=moldboard plowing, CH=chisel plowing or NT=no-tillage) in a corn-soybean (Glycine max (L.) Merrill) rotation since 1991 as main treatments. Four subtreatments: (i) subsoil (paratill subsoiler to 40 cm depth in fallow 1995)+N fertilization (100 kg ha(-1) N as ammonium nitrate, at the V6 development stags of corn), (ii) subsoil+no N fertilization, (iii) no subsoiling+N fertilization, and (iv) no subsoiling+no N fertilization. Chemical and physical properties in the top layer of the soils were determined at seeding in 1995. Penetration resistance was measured at seeding, flowering and at harvest in 1995 and at seeding in 1997. Corn shoot dry matter during vegetative stages and grain yield components were also determined. The preparation of seedbed using either moldboard or chisel plowing with or without deep-tillage, increased the vegetative biomass by 27% and the grain yield of the corn crops by 9% over the no-tillage system. Subsoiling no-till plots improved the vegetative growth of the crops, but the effect of the deep-tillage did not modify the corn grain yields. Grain yields were strongly related to the N fertilization treatments. Although bulk density values (BD) ranged between 1.05 and 1.33 Mg m(-3) differences in crop yields were attributed to differences in the ED and the N fertilization. In the western Pampas Region of Argentina, the production of high yielding corn crops, under no water stress conditions, is independent of the tillage systems but negatively related with the soil BD values, and positively dependent on N fertilization.
  • Authors:
    • Reule, C. A.
    • Halvorson, A. D.
    • Anderson, R. L.
  • Source: Journal of Soil and Water Conservation
  • Volume: 55
  • Issue: 1
  • Year: 2000
  • Summary: Minimum-till (MT) and no-till (NT) systems were evaluated for converting seeded grassland back to cropland. Nitrogen fertilization needs to optimize grain yields following grass and to optimize hay yields from the grassland were also evaluated. Tillage treatments - conventional till (CT), MT, and NT- were established on a Weld silt loam soil that had been seeded to grass about 30 yr following more than 30 yr of crop-fallow. Nitrogen treatments were 0, 45, and 30 kg N/hn (0, 40, and 80 lb N/a) applied to each crop in a winter wheat (Triticum aestivum L.)-corn (Zea mays L.)-fallow rotation or annually to grass plots. Residue cover at wheat planting averaged 18, 44, and 73% for CT; MT; and NT; respectively Soil water recharge was minimal between grass kill and wheat planting; however soil NO3-N increased 115, 63, and 54 kg N/ha (103, 62, and 48 lb N/ac) for CT, MT, and NT respectively. Wheat grain yields were greater with CT 2,685 kg/ha (40 bu/ac) and MT 2,558 kg/ha (38 bu/ac) than with NT 2,052 kg/ha (30.5 bu/ac). Lower wheat yields with NT resulted from lack of grass control Wheat yield responses to N varied with year and were dependent on available water supplies. Corn grain yields were low, [1,233, 2,063, and 1,564 kg/ha (19.7, 32.9, and 24.9 bu/ac) for CT; MT, and NT; respectively] due to limited growing season water. Average wheat 6,298 kg/ha (5,623 lb/ac) and corn 5,040 kg/ha (4,500 lb/ac) phytomass production exceeded that of the fertilized grass [1,529 kg/ha with 90 kg N/ha (1,365 lb/ac with 80 lb N/ac)]. Producers converting CRP grass to crop production can use MT and NT practices to maintain soil erosion control.
  • Authors:
    • Rhoton, F. E.
  • Source: Soil Science Society of America Journal
  • Volume: 64
  • Issue: 2
  • Year: 2000
  • Summary: The number of growing seasons required for no-till practices to improve soil properties should be considered before changing management systems. To evaluate this time factor, an 8-yr tillage study was conducted on a Grenada silt loam (fine-silty, mixed, active, thermic Glossic Fragiudalfs) using cotton (Gossypium hirsutum L.), grain sorghum [Sorghum bicolor (L.) Moench]-corn (Zea mays L.), and soybean [Glycine max (L.) Merr.]-wheat (Triticum aestivum L.) as test crops. Soil samples were characterized for soil organic matter (SOM), pH, exchangeable Ca and Mg, extractable P, K, Fe, Mn, Cu, and Zn, aggregate stability (AS), water dispersible clay (WDC), total clay (TC), and modulus of rupture (MR) at time 0, 4, and 8 yr. Within 4 yr, no-till (NT) resulted in statistically significant (P less than or equal to 0.05) differences compared to conventional tillage (CT). The surface 2.5 cm of the NT treatments had higher levels of SOM, exchangeable Ca, and extractable P, Mn, and Zn, but lower extractable K, Fe, and Cu. Tillage had no effect on exchangeable Mg and pH. No-till also resulted in higher AS, and lower MR, WDC, and TC in the top 2.5 cm, relative to CT. The differences in soil properties between tillage treatments were essentially independent of crop. Instead, the results are controlled by relative amounts of SOM and clay, and the extent to which these properties change with time. Undoubtedly, NT practices ran improve several fertility and erodibility-related properties of this soil within 4 yr, and-enhance its sustainability.
  • Authors:
    • Harwood, R. R.
    • Paul, E. A.
    • Robertson, G. P.
  • Source: Science
  • Volume: 289
  • Issue: 5486
  • Year: 2000
  • Summary: Agriculture plays a major role in the global fluxes of the greenhouse gases carbon dioxide, nitrous oxide, and methane. From 1991 to 1999, we measured gas fluxes and other sources of global warming potential (GWP) in cropped and nearby unmanaged ecosystems. Net GWP (grams of carbon dioxide equivalents per square meter per year) ranged from 110 in our conventional tillage systems to 2211 in early successional communities. None of the annual cropping systems provided net mitigation, although soil carbon accumulation in no-till systems came closest to mitigating all other sources of GWP. In all but one ecosystem, nitrous oxide production was the single greatest source of GWP. In the late successional system, GWP was neutral because of significant methane oxidation. These results suggest additional opportunities for lessening the GWP of agronomic systems.
  • Authors:
    • Samu, F.
    • Sunderland, K.
  • Source: Entomologia Experimentalis Et Applicata
  • Volume: 95
  • Issue: 1
  • Year: 2000
  • Summary: A review of the literature showed that spider abundance was increased by diversification in 63% of studies. A comparison of diversification modes showed that spider abundance in the crop was increased in 33% of studies by `aggregated diversification' (e.g. intercropping and non-crop strips) and in 80% of studies by `interspersed diversification' (e.g., undersowing, partial weediness, mulching and reduced tillage). It is suggested that spiders tend to remain in diversified patches and that extending the diversification throughout the whole crop (as in interspersed diversification) offers the best prospects for improving pest control. There is little evidence that spiders walk in significant numbers into fields from uncultivated field edges, but diversification at the landscape level serves to foster large multi-species regional populations of spiders which are valuable as a source of aerial immigrants into newly planted crops. There are very few manipulative field studies where the impact of spiders on pests has been measured in diversified crops compared with undiversified controls. It is encouraging, however, that in those few studies an increased spider density resulted in improved pest control. Future work needs are identified.
  • Authors:
    • TCG
    • Teasdale,John R.
    • Rosecrance,R. C.
    • Coffman,Charles B.
    • Starr,J. L.
    • Paltineanu,I. C.
    • Lu,Y. C.
    • Watkins,B. K.
  • Source: American Journal of Alternative Agriculture
  • Volume: 15
  • Issue: 2
  • Year: 2000
  • Summary: Sustainable production systems are needed to maintain soil resources and reduce environmental contamination on erodible lands that are incompatible with tillage-intensive operation. A long-term cropping systems comparison was established at Beltsville, Maryland, on a site with 2 to 15% slope to evaluate the efficacy of sustainable strategies compatible with reduced-tillage systems. All systems followed a 2-year rotation of corn the first year and winter wheat followed by soybean the second year. Treatments included (1) no-tillage system with recomended fertilizer and herbicide inputs, (2) crownvetch living mulch system with similar inputs to the no-tillages system, (3) cover crop system including a hairy vetch cover crop before corn and a wheat cover crop before soybean with reduced fertilizer and herbicide inputs, (4) manure systemd including crimson clover green manure plus cow manure for nutrient sources, chisel plow/disk for incorporatin manure and rotary hoe plus cultication for weed control. Results from the initial 4 years demonstrated the relative productivity of these systems. Corn yields were similar in the no-tillage and cover crop systems in each year. both systems average 7.8 Mg ha-1 compared to 5.7 Mg ha-1 in both the croen vetch and manure systems. Wheat yields were highest in the manure system in the first 2 years and in the crown vetch system in the last 2 years. Soybean yields were highest in the cover crop system in all years. The manure system usually had lower yields than the highest yielding system, partly because of competitions from uncontrolled weeds. Several measures of the efficience of grain production were evaluated. The no-tillage system produced the most grain per total vegetative biomass throughout the rotation. The cover crop system produced the most grain per unit of external N input and, along with the no-tillage system, had the highest corn water-use efficiency. The cover crop system also recycled the most vegetative residues and nutrients of all systems. No single system perfomed best according to all measures of comparison, suggesting that trade-offs will be required when choosing production systems.