Soil Chemical Analysis

B6nassy, C., 1955. R6marques sur deux Aphelinid6s: Aphelinus mytilaspidis Le Baron et Aphytis proclia Walker. Annls l~piphyt. 6: 11-17. Lord, F. T. & MacPhee, A. W., 1953. The influence of spray programs on the fauna of apple orchards in Nova Scotia II. Oyster shell scale. Can. Ent. 79: 196-209. Pickett, A. D., 1946. A progress report on long term spray programs. Rep. Nova Scotia Fruit Grow. Ass. 83 : 27-31. Pickett, A. D., 1967. The influence of spray programs on the fauna of apple orchards in Nova Scotia XIV. Can. Ent. 97: 816-821. Tothill, J. D., 1918. The predacious mite Hemisarcoptes malus Shimer and its relation to the natural control of the oyster shell scale Lepidosaphes ulmi L. Agric. Gaz. Can. 5 : 234-239.

http://link.springer.com/content/pdf/10.1007/BF01976688.pdf

Soil enzymes: Kuprevich, V. F. & Shcherbakova, T. A.: Translated from the Russian edition (1966), published by the Indian National Scientific Documentation Centre, New Delhi 1971. 392 pp., offset printing from type script, paper cover. Obtainable from U.S. Department of Commerce, National Technical Information Service, Springfield, Va. 22151

In order to better assess the role of agriculture within the global climate-vegetation system, we present a model of the managed planetary land surface, Lund-Potsdam-Jena managed Land (LPJmL), which simulates biophysical and biogeochemical processes as well as productivity and yield of the most important crops worldwide, using a concept of crop functional types (CFTs). Based on the LPJ-Dynamic Global Vegetation Model, LPJmL simulates the transient changes in carbon and water cycles due to land use, the specific phenology and seasonal CO2 fluxes of agricultural-dominated areas, and the production of crops and grazing land. It uses 13 CFTs (11 arable crops and two managed grass types), with specific parameterizations of phenology connected to leaf area development. Carbon is allocated daily towards four carbon pools, one being the yield-bearing storage organs. Management (irrigation, treatment of residues, intercropping) can be considered in order to capture their effect on productivity, on soil organic carbon and on carbon extracted from the ecosystem. For transient simulations for the 20th century, a global historical land use data set was developed, providing the annual cover fraction of the 13 CFTs, rain-fed and/or irrigated, within 0.5 degrees grid cells for the period 1901-2000, using published data on land use, crop distributions and irrigated areas. Several key results are compared with observations. The simulated spatial distribution of sowing dates for temperate cereals is comparable with the reported crop calendars. The simulated seasonal canopy development agrees better with satellite observations when actual cropland distribution is taken into account. Simulated yields for temperate cereals and maize compare well with FAO statistics. Monthly carbon fluxes measured at three agricultural sites also compare well with simulations. Global simulations indicate a similar to 24% (respectively similar to 10%) reduction in global vegetation (respectively soil) carbon due to agriculture, and 6-9 Pg C of yearly harvested biomass in the 1990s. In contrast to simulations of the potential natural vegetation showing the land biosphere to be an increasing carbon sink during the 20th century, LPJmL simulates a net carbon source until the 1970s (due to land use), and a small sink (mostly due to changing climate and CO2) after 1970. This is comparable with earlier LPJ simulations using a more simple land use scheme, and within the uncertainty range of estimates in the 1980s and 1990s. The fluxes attributed to land use change compare well with Houghton's estimates on the land use related fluxes until the 1970s, but then they begin to diverge, probably due to the different rates of deforestation considered. The simulated impacts of agriculture on the global water cycle for the 1990s are similar to 5% (respectively similar to 20%) reduction in transpiration (respectively interception), and similar to 44% increase in evaporation. Global runoff, which includes a simple irrigation scheme, is practically not affected. (Less)

Modelling the role of agriculture for the 20th century global terrestrial carbon balance

Positive ions that are available in soils absorb on grain surfaces. The total sum of cations that can be absorbed bij a soil/sediment at a certain PH is defined by the cation-exchange capacity (CEC, in meq g-1: mol equivalents per gram). The uptake of cations is an important parameter in agriculture and the larger the CEC, the more cations can be absorbed to the soil. The CEC depends highly on the pH of soil and sediments, where the CEC decreases with decreasing PH (increasing acidity). The exchange of ions on sediments occurs commonly fast on geological time scales, but the kinetics of adsorption in natural environments is still poorly understood. The strength of the bonding between the cations and the sediments varies from weak Van der Waals bondings (physical adsorption) to strong chemical bonds. The CEC is widely used for agricultural assessment because it is a measure of general soil fertility as well as an indicator of structural stability because CED is capabel of enhancing development of shrinkage cracks. The list below shows the CEC for different types of minerals. The data indicate that the CEC can vary over 2 orders of magnitude for various types of , minerals and can vary one order of magnitude within one soil type. Cation exchange capacity for different types of sediment (Eisma, 1992; Locher and de Bakker, 1990):

Cation exchange capacity.

Nitrate (NO3
−) leaching from agriculturalproduction systems is blamed for the rising concentrations ofNO3
− in ground- and surface-waters around the world.This paper reviews the evidence of NO3
− leachinglosses from various land use systems, including cut grassland, grazed pastures,arable cropping, mixed cropping with pasture leys, organic farming,horticultural systems, and forest ecosystems. Soil, climatic and managementfactors which affect NO3
− leaching are discussed.Nitrate leaching occurs when there is an accumulation ofNO3
− in the soil profile that coincides with or isfollowed by a period of high drainage. Therefore, excessive nitrogen (N)fertilizer or waste effluent application rates or N applications at the wrongtime (e.g. late autumn) of the year, ploughing pasture leys early in the autumn,or long periods of fallow ground, can all potentially lead to highNO3
− leaching losses. N returns in animal urine havea major impact on NO3
− leaching in grazed pastures.Of the land use systems considered in this paper, the potential for causingNO3
− leaching typically follow the order: forest< cut grassland < grazed pastures, arable cropping < ploughing ofpasture < market gardens. A range ofmanagement options to mitigate NO3
− leaching isdescribed, including reducing N application rates, synchronizing N supply toplant demand, use of cover crops, better timing of ploughing pasture leys,improved stock management, precision farming, and regulatory measures. This isfollowed by a discussion of future research needs to improve our ability topredict and mitigate NO3
− leaching.

Nitrate leaching in temperate agroecosystems: sources, factors and mitigating strategies

Intensification of rice-based cropping systems in Asia has substantially increased production of food and associated crop residues. The interval between crops in these systems is often brief, making it attractive for farmers to burn residues in the field to hasten and facilitate tillage for the next crop. Open-air burning causes serious air quality problems affecting human health and safety, and it has been banned by many Asian governments. In this chapter, we evaluate for rice-based cropping systems existing and emerging in-field alternatives to burning residues based on criteria of productivity, profitability, environmental impact, and sustainability. In intensive rice monocropping systems, residue is typically managed under conditions of soil flooding and anaerobic decomposition during the rice crop. In systems, where rice is rotated with an upland (non-flooded) crop, there are two major categories: residue of upland crop managed during flooded rice and rice residue managed during the upland crop. One option during the flooded rice crop is incorporation of residues from the previous rice or upland crop into the soil. Many studies have examined incorporation of crop residue during land preparation for flooded rice. In the vast majority of cases there was no significant increase in yield or profit. Residue decomposition in anaerobic flooded soil substantially increases methane (CH 4 ) emission relative to residue removal. Surface retention of residue during rice cropping is challenging to implement because residue must be removed from the field during conventional tillage with soil flooding (i.e., puddling) and then returned. Alternatively, rice must be established without the traditional puddling that has helped sustain its productivity. Mulch is a good option for rice residue management during the upland crop, especially with reduced and no tillage. Mulch can increase yield, water use efficiency, and profitability, while decreasing weed pressure. It can slightly increase nitrous oxide (N 2 O) emission compared with residue incorporation or removal, but N fertilization and water management are typically more important factors controlling N 2 O emission than residue management. Long-term studies of residue removal have indicated that removing residue from continuous rice systems with near continuous soil flooding does not adversely affect soil organic matter (SOM). The use of crop residue as a mulch with reduced or no tillage for upland crops should be promoted in rice-based cropping systems. On the contrary, residues from the crop preceding rice on puddled and flooded soil can be considered for removal for off-field uses.

Chapter 3 Crop Residue Management for Lowland Rice-Based Cropping Systems in Asia

The sustainability of the rice (Oryza sativa L.)-wheat (Triticum aestivum L.) rotation is important to Asia's food security. Intensive cropping with no return of crop residues and other organic inputs result in the loss of soil organic matter (SOM) and nutrient supply, and is assumed to be nonsustainable. We evaluated seven treatments comprised of various combinations of green manure (GM; Sesbania cannabina L.); wheat straw (WS), farmyard manure (FYM), and urea on yields and yield trends; P and K balance; and soil fertility in a rice-wheat experiment (1988-2000) on a loamy sand in Punjab, India. Rice yields were comparable with GM + urea, WS + GM + urea, and urea alone, but yields were reduced when FYM was supplemented with N. Except during 1 yr, integrated use of FYM and GM produced equal or higher rice yields than other GM based treatments. Wheat straw incorporation reduced average rice yields by 7% compared with WS removal. After 5 yr of continuous application, FYM and WS were at par in increasing rice yields. Organic materials applied to rice had no residual effect on wheat yields except FYM, which increased yield by about 6% compared with urea alone. Rice yield declined by 0.02 to 0.13 Mg ha -1 yr -1 but wheat yields remained unchanged. Soil C increased with the application of WS and FYM. Potassium balance was highly negative. Although the causes of yield decline are unknown, inadequate K applications and changes in the climatic parameters are possible reasons.

Long-term effects of organic inputs on yield and soil fertility in the rice-wheat rotation

Rice (Oryza saliva L.)-wheat (Triticum aestivum L.) farmers in India burn or remove residues to facilitate seedbed preparation. Incorporation of residues before planting of the next crop generally decreases yields due to N immobilization. Since a window of about 40 d is available between rice harvest and wheat planting, the effect of time of incorporation on rice residue decomposition and N mineralization-immobilization was studied in 1992-1993. The mass loss of residue was 25% for a 10-d, 35% for a 20-d, and 51% for a 40-d decomposition period before wheat planting. Nitrogen release from residue ranged from 6 to 9 kg ha -1 during the wheat season. The immobilization of urea N decreased when residue was allowed to decompose for 10-d or longer. Based on these studies, a long-term (1993-2000) experiment was conducted on a sandy loam soil to examine the effect of time of residue incorporation before sowing wheat when compared with burning or removal of residue on yields, N-use efficiency, and soil fertility. The effect of wheat residue incorporation with green manure (GM, Sesbania cannabina L.) on subsequent rice yields was also determined. Residue incorporation for 10 to 40 d had no effect on wheat yields. Rice yields increased (0.18-0.39 Mg ha -1 ) when wheat residue was incorporated with GM. Starter N applied at residue incorporatidn did not influence wheat yields but decreased N recovery efficiency. Physiological efficiency was higher when rice straw was incorporated in wheat and when wheat straw plus GM were incorporated in rice than when rice straw was incorporated for 10 d or when the straw was burned. The long-term application of rice residue increased C accumulation in soil.

http://indiaenvironmentportal.org.in/files/effects%20of%20residue%20decomposition%20on%20productivity%20and%20soil%20fertility%20in%20RWC.pdf

Effects of Residue Decomposition on Productivity and Soil Fertility in Rice–Wheat Rotation

Integrating fertilizer N (FN) with legume green manures (GM) can foster sustainable and environmentally sound agricultural systems in subtropical, semiarid soils low in organic matter. A 4-yr replicated field experiment with irrigated rice (Oryza sativa L.) and wheat (Triticum aestivum L.) rotations was conducted on a sandy loam soil in the Punjab of India to evaluate the effects of incorporating cowpea (Vigna unguiculata L.) or sesbania (Sesbania aculeata L.) GM on crop productivity, N-use efficiency, and NO 3 leaching. Rice grain yields with pretransplant incorporation of 20 and 40 Mg GM ha -1 (GM 20 and GM 40 ) ranged from 5.18 to 5.81 Mg ha -1 , which were equivalent to the 5.40 Mg ha -1 obtained with 120 kg FN ha -1 (FN 120 ). Rice yield with 60 kg FN ha -1 (FN 60 ) and GM 20 was double the control yield and 6% greater than the FN 120 treatment. Nitrogen utilization by rice was greater for GM 20 than FN, as indicated by greater fertilizer N equivalents and an apparent N recovery by rice of 79 vs. 63%. While FN had no residual effects, residual GM produced greater wheat yields, indicating that FN applied to wheat could be reduced by 25%. Soil NO 3 -N leaching to 60 cm in the rice crop was apparently used by the subsequent wheat crop, which has a deeper and more extensive rooting system. After 4 yr, use of FN 120 for both crops resulted in 35 kg of residual NO 3 -N ha -1 in the 150-cm soil profile (74% below 90 cm), whereas only 19 kg NO 3 -N ha -1 remained with GM 20 plus FN 60 . Use of GM 20 with FN 60 for a rice-wheat rotation demonstrated greater yields of rice and wheat, 25 to 50% reduction in fertilizer N use, and decreased potential for groundwater NO 3 contamination.

/pdf/yields-and-nitrogen-dynamics-in-a-rice-wheat-system-using-511p5oqd52.pdf

Yields and nitrogen dynamics in a rice-wheat system using green manure and inorganic fertilizer.

Porous soils are characterized by high infiltration, low moisture retention and poor fertility due to limitation of organic matter and nitrogen (N). However, wherever irrigated and properly managed, these are among the most productive soils in the world. For sustained productivity and prevention of N related pollution problems, fertilizer N management in porous soils needs to be improved by reducing losses of N via different mechanisms. Losses of N through ammonia volatilization are not favoured in porous soils provided fertilizer N is applied before an irrigation or rainfall event. Ammonium N transported to depth along with percolating water cannot move back to soil surface where it is prone to be lost as NH3. Under upland conditions nitrification proceeds rapidly in porous soils. Due to high water percolation rates in porous soils, continuous flooding for rice production usually cannot be maintained and alternate flood and drained conditions are created. Nitrification proceeds rapidly during drained conditions and nitrates thus produced are subsequently reduced to N2 and N2O through denitrification upon reflooding. Indirect N-budget estimates show that up to 50% of the applied N may be lost via nitrification-denitrification in irrigated porous soils under wetland rice. High soil nitrate N levels and sufficient downward movement of rain water to move nitrate N below the rooting depth are often encountered in soils of humid and subhumid zones, to a lesser extent in soils of semiarid zone and quite infrequently, if at all in arid zone soils. The few investigations carried out with irrigated porous soils do not show substantial leaching losses of N beyond potential rooting zone even under wetland rice. However, inefficient management of irrigation water and fertilizer N particularly with shallow rooted crops may lead to pollution of groundwater due to nitrate leaching. At a number of locations, groundwater beneath irrigated porous soils is showing increased nitrate N concentrations. Efficient management of N for any cropping system in irrigated porous soils can be achieved by plugging losses of N via different mechanisms leading to both high crop production and minimal pollution of the environment.

Bijay-Singh

Papers

Chapter 3 Crop Residue Management for Lowland Rice-Based Cropping Systems in Asia

Long-term effects of organic inputs on yield and soil fertility in the rice-wheat rotation

Effects of Residue Decomposition on Productivity and Soil Fertility in Rice–Wheat Rotation

Yields and nitrogen dynamics in a rice-wheat system using green manure and inorganic fertilizer.

Nitrogen losses and fertilizer N use efficiency in irrigated porous soils