Cotton Wheat Research Articles

Differences in Soil Properties Between Irrigation and Cropping Sequences in the Thar Desert of India

Watering is known to convert deserts into oases. However, information on how irrigation brings changes in physical and chemical properties of soils in a desert biome is not yet known, though pertinent to land use planning. This study reports influence of irrigation and cropping sequence on physico-chemical properties of soils in the Thar Desert, Rajasthan, India. Treatments included three irrigation conditions (not irrigated, low-irrigated, and high-irrigated) and eleven cropping sequences, cotton-gram (C-G), mung bean-mustard (M-Mu), moth bean-wheat (Mo-W), moth bean-mustard (Mo-Mu), cotton-fallow (C-F), cotton-wheat (C-W), cotton-mustard (C-Mu), mung bean-wheat (M-W), moth bean-fallow (Mo-F), mung bean-fallow (M-F), and pearl millet-fallow (P-F). The irrigation reduced soil temperature (9.7 to 12.2%) and bulk density (5.3 to 6.6%), but increased silt (5.1 to 7.2%) and clay (3.8 to 5.4%) content, water holding capacity (50 to 58.3%), moisture content at field capacity (100 to 133.3%), concentration (2.3 to 3.1 times), and stock (2.2 to 3.0 times) of soil organic carbon (SOC), microbial biomass carbon (4 to 8 times), available phosphorus (1.82 to 2.1 times), and potassium (25.9 to 67.1%). These changes were higher in the high-irrigated than the low-irrigated conditions. Cropping sequences C-W, C-Mu, and C-G sequestered more SOC and retained higher microbial biomass carbon, whereas M-Mu, Mo-W, Mo-Mu and M-W maintained the highest level of phosphorus and potassium. These observations suggest that irrigation and cropping sequence are promising management options for enhancing carbon sequestration in soils, which may reduce desertification in the Thar Desert and other similar deserts in the hot tropics.

Deep drainage in a Grey Vertosol under furrow-irrigated cotton

Deep drainage under irrigated cotton is not only a waste of a scare resource but also has the potential to cause groundwater levels to rise and cause salinity. Drainage is difficult and expensive to measure directly, so most estimates have relied on modelling or chloride mass-balance calculations. However, direct, accurate measurements of drainage are required to understand drainage processes in cracking clay soils and to provide some certainty about other estimates. A variable-tension lysimeter was installed at 2.1 m depth in a Grey Vertosol under a furrow-irrigated, cotton–wheat rotation. The collection trays were installed without disturbing the overlying soil. A vacuum was applied to the trays and was continuously adjusted to match the matric potential in the surrounding soil at the same depth, thus maintaining the same hydraulic gradient as in the surrounding soil. The lysimeter was used to measure drainage and other components of the water balance from 2006 to 2011, including three cotton crops, one wheat crop and a long fallow. During this period, two types of drainage were observed. Matrix drainage occurred after an extended period during which rainfall exceeded evapotranspiration. This caused a wetting front to move through the soil over a period of months until it reached the lysimeter and was measured as drainage. Matrix drainage extended over a period of 1 month but at a low rate of ~0.5 mm/day. During the cotton season, the earlier irrigations generally caused a sharp peak in drainage of up to 3.5 mm day–1 ~25 h after irrigation. However, the water content and soil-water potential at 2.1 m were largely unaffected, and in some cases, the hydraulic gradient was upwards while drainage was occurring. This suggests this drainage is caused by irrigation flowing rapidly through the profile bypassing the soil matrix. Later in the season, when soil-water deficits developed in the subsoil at 0.5–1.0 m between irrigations, the peaks in drainage rate became much smaller. Bypass drainage appears to account for most of the drainage during the measurement period. Apart from lowering the water use efficiency, it is also more unpredictable and difficult to manage. In addition, bypass drainage is less efficient at removing salt from the soil profile, so that a higher leaching fraction may be required to prevent excessive salt accumulation.

Impact of Carbohydrates and Mineral Contents of Different Indigenous Strains of Oyster Mushroom (Jacq. Fr.) Cultivated on Different Agricultural Wastes

Different strains of Pleurotus ostreatus were cultivated on different agro-cellulosic wastes viz. cotton waste, wheat straw and paddy straw to determine the effect of these agro wastes on biological efficiency, carbohydrate and mineral contents including Na, K, Ca, Cu, Zn and Fe. Maximum biological efficiency was recorded on P. ostreatus (grey strain, 134.4%) and (white strain, 113.7%) on wheat straw. P. sajor-caju showed maximum biological efficiency (195.9%) on wheat straw. Maximum amount of Na was found (0.18g/100g) on P. ostreatus (grey strain) and K was found on P. sajor-caju (4.58g/100g) cultivated on paddy straw followed by wheat straw and cotton waste. P. ostreatus (white strain) cultivated on paddy straw showed maximum amount of Cu (0.0009g/100g) while maximum amount of Zn was found (0.017g/100g) on P. ostreatus (white strain). Maximum amount of Fe was found (0.008g/100g) on P. sajor-caju cultivated on cotton waste. P. sajor-caju cultivated on cotton waste showed significantly highest carbohydrate (0.079g/100g).

NUTRIENT BALANCES AS AFFECTED BY INTEGRATED NUTRIENT AND CROP RESIDUE MANAGEMENT IN COTTON-WHEAT SYSTEM IN ARIDISOLS. I. NITROGEN

A five-year cotton–wheat rotation field experiment was conducted on two alkaline-calcareous soils, i.e., Awagat (coarse loamy) and Shahpur (fine silty), to investigate the impact of integrated nutrient and crop residue management on soil and crop productivity. Apparent nitrogen (N) balances were developed. Minimum five-year mean yield (Mg ha−1), obtained with Farmers’ Fertilizer Use (FFU) treatment was: cotton – Awagat, 2.19; Shahpur, 2.45; wheat – Awagat, 3.03; Shahpur, 3.94. With Balance Nutrient Management (BNM), yields increased (P ≤ 0.05) for cotton, 24% in Awagat and 18% in Shahpur soil; and wheat, 37% in Awagat and 24% in Shahpur soil. Maximum crop yields were obtained with Integrated Nutrient Management (INM), i.e., 3–5% higher than with BNM. Crop residue recycling increased the yields further, cotton by 2−7% and wheat by 2–10%. All nutrient management treatments, except for FFU without crop residue recycling, resulted in positive apparent N balances. INM improved SOM and NO3-N, contents.

Soil properties, black root-rot incidence, yield, and greenhouse gas emissions in irrigated cotton cropping systems sown in a Vertosol with subsoil sodicity

Comparative studies of soil quality and energy use in two- and three-crop rotations in irrigated cotton (Gossypium hirsutum L.) based cropping systems under varying stubble management practices in Australian Vertosols are sparse. Our primary objective was to quantify selected soil quality indices (salinity, sodicity, exchangeable cations, nitrate-N, pH), crop yields, and greenhouse gas emissions in four irrigated cotton-based cropping systems sown on permanent beds in a Vertosol with subsoil sodicity near Narrabri in north-western New South Wales. A secondary objective was to evaluate the efficacy of sowing vetch in rotation with cotton over a long period on the incidence of black root-rot in cotton seedlings. Results presented in this report pertain to the period June 2005–May 2011. The experimental treatments were: cotton–cotton; cotton–vetch (Vicia benghalensis L.); cotton–wheat (Triticum aestivum L.), where wheat stubble was incorporated; and cotton–wheat–vetch, where wheat stubble was retained as in-situ mulch. Vetch was terminated during or just before flowering by a combination of mowing and contact herbicides, and the residues were retained as in-situ mulch. Soil pH, electrical conductivity (EC1 : 5), Cl–, NO3–-N, exchangeable cations, exchangeable sodium percentage (ESP), electrochemical stability index (= EC1 : 5/ESP), and EC1 : 5/ESC (exchangeable sodium concentration) were evaluated in samples taken from the 0–1.2 m depth before sowing cotton during late September or early October of each year. Incidence of black root-rot was assessed 6 weeks after sowing cotton. Compared with sowing cotton every year, including wheat in cotton-based cropping systems improved cotton yield and reduced soil quality decline, emissions of carbon dioxide equivalents (CO2-e) per unit area, and CO2-e emissions per unit of cotton yield. Including vetch in the rotation was of negligible benefit in terms of yield and CO2-e emissions per unit of yield. The rate of soil quality decline was unaffected by including vetch in a cotton–wheat rotation but was accelerated when included in a cotton–cotton sequence. Among all cropping systems, soil quality was best with cotton–wheat and cotton–wheat–vetch but poorest with cotton–vetch. Although CO2-e emissions associated with growing 1 ha of cotton could be reduced by 9% by growing vetch because of substituting fixed atmospheric N for N fertiliser derived from fossil fuels, this advantage was partly negated by the emissions from farming operations associated with growing a vetch crop. Relative to a two-crop rotation (one cotton–one rotation crop), negligible benefits in terms of yield, soil quality, greenhouse gas emissions, and black root-rot control accrued from a three-crop rotation (one cotton–two rotation crops). Incidence of black root-rot increased as the number of cotton crops sown increased. In addition to the cropping systems, soil quality indices and yield were significantly influenced by irrigation water quality and climate.

Carbon inputs by wheat and vetch roots to an irrigated Vertosol

Research on the amounts of carbon that can be added to Vertosols of New South Wales and Queensland by crop roots in irrigated cotton farming systems is sparse. The objective of this study was to determine the amounts of carbon added to soil by roots of wheat (Triticum aestivum L.) and purple vetch (Vicia benghalensis L.) sown in rotation with irrigated cotton (Gossypium hirsutum L.). Measurements were made from 2008 to 2010 in an ongoing experiment near Narrabri, northern NSW, using a combination of soil cores and minirhizotron observations. The experimental treatments were: cotton monoculture; cotton–vetch (CV); cotton–wheat, in which wheat stubble was incorporated into the beds with a disc-hiller (CW); and cotton–wheat–vetch, in which wheat stubble was retained as in-situ mulch (CWV). Vetch was killed by a combination of mowing and contact herbicides, and the residues were retained as in situ mulch. Root length per unit area of vetch in CWV and wheat in both CW and CWV was comparable, although wheat had a higher concentration of roots in surface 0.10 m. Root growth of the CV treatment was sparse. Root carbon available for addition to soil was greater with vetch than with wheat and was in the order: vetch in CWV (5.1 t C/ha.year) > vetch in CV (1.9 t C/ha.year) > wheat in CW (1.6 t C/ha.year) = wheat in CWV (1.7 t C/ha.year). Intra-seasonal root mortality accounted for 12% of total root carbon in vetch and 36% in wheat. The remaining fraction consisted of carbon in the root mass at the end of the growing season. Carbon sequestered by root inputs of the rotation crops was estimated to be ~0.34 t C/ha.year for the vetch and wheat crops in the CWV rotation, 0.10 t C/ha.year for vetch in CV, and 0.08 t C/ha.year for wheat in CW. Rotation CWV was, therefore, the most effective in sequestering carbon from roots.

Soil water storage, drainage, and leaching in four irrigated cotton-based cropping systems sown in a Vertosol with subsoil sodicity

Comparative studies of drainage and leaching in irrigated cotton (Gossypium hirsutum L.) based cropping systems in Australian Vertosols are sparse. Our objective was to quantify soil water storage, drainage, and leaching in four cotton-based cropping systems sown on permanent beds in an irrigated Vertosol with subsoil sodicity. Drainage was inferred using the chloride mass-balance method, and soil water storage and leaching were measured with a neutron moisture meter and ceramic-cup water samplers, respectively, from September 2005 to May 2011 in an ongoing experiment. The experimental treatments were: CC, cotton monoculture, summer cotton with winter fallow; CV, cotton–vetch (Vicia benghalensis L.) rotation with vetch stubble retained as in-situ mulch; CW, cotton–wheat (Triticum aestivum L.), with wheat stubble incorporated and a summer–winter fallow; and CWV, cotton–wheat–vetch, with wheat and vetch stubbles retained as in-situ mulch and summer and spring fallows. Soil water storage was generally highest under CW and CWV and least under CV. An untilled short fallow (~3 months) when combined with retention of crop residues as surface mulch, as in CWV, was as effective in harvesting rainfall as a tilled long fallow (~11 months) with stubble incorporation, as in CW. Drainage under cotton was generally in the order CW ≥ CWV > CC = CV, all of which were considerably greater than drainage during fallows. Except for very wet and dry winters, drainage under wheat rotation crops was greater than that under vetch. During wet winters, saturated soil in the 0–0.6 m depth of treatments under fallow resulted in more drainage than in the drier, cropped plots. No definitive conclusions could be made with respect to the effects of cropping systems on salt and nutrient leaching. Leachate contained less nitrate-nitrogen, magnesium, and potassium, but leachate electrical conductivity was ~6 times higher than infiltrated water. The greater salinity of the leachate may pose a risk to groundwater resources.

Impact of Integrated Weed Management on Cotton Producers' Earnings in Pakistan*

In Pakistan, weeds are a serious problem for the cotton–wheat cropping system, and they are causing even more damage than insects. The damage caused by weeds varies in the range of 15–30 percent. Farmers in Pakistan carry out several practices to control weeds, including hoeing, herbicide application and crop rotation. Farmers integrate different weed management practices; hence, in the present study, the multivariate probit model is used in an analysis of cotton farmers' joint decision-making. The propensity score matching results indicate that farmers adopting integrating weed management practices have higher demand for labor, higher yields, higher household income and higher net returns from the cotton crop.

Soil carbon sequestration and associated economic costs for farming systems of the Indo-Gangetic Plain: A meta-analysis

Soil organic carbon sequestration rates over 20 years based on the Intergovernmental Panel for Climate Change (IPCC) methodology were combined with local economic data to determine the potential for soil C sequestration in wheat-based production systems on the Indo-Gangetic Plain (IGP). The C sequestration potential of rice–wheat systems of India on conversion to no-tillage is estimated to be 44.1 Mt C over 20 years. Implementing no-tillage practices in maize–wheat and cotton–wheat production systems would yield an additional 6.6 Mt C. This offset is equivalent to 9.6% of India's annual greenhouse gas emissions (519 Mt C) from all sectors (excluding land use change and forestry), or less than one percent per annum. The economic analysis was summarized as carbon supply curves expressing the total additional C accumulated over 20 year for a price per tonne of carbon sequestered ranging from zero to USD 200. At a carbon price of USD 25 Mg C −1, 3 Mt C (7% of the soil C sequestration potential) could be sequestered over 20 years through the implementation of no-till cropping practices in rice–wheat systems of the Indian States of the IGP, increasing to 7.3 Mt C (17% of the soil C sequestration potential) at USD 50 Mg C −1. Maximum levels of sequestration could be attained with carbon prices approaching USD 200 Mg C −1 for the States of Bihar and Punjab. At this carbon price, a total of 34.7 Mt C (79% of the estimated C sequestration potential) could be sequestered over 20 years across the rice–wheat region of India, with Uttar Pradesh contributing 13.9 Mt C.

Effect of tillage and nutrient management on wheat productivity and quality in Haryana, India

This article reports on field experiments with 4 different rotations that are commonly used throughout Haryana in NW India (rice–wheat, cotton–wheat, pearl millet–wheat, cluster bean–wheat), where we assess wheat yield and chapatti quality measures with different crop establishment methods and input of micronutrients. In a series of experiments conducted on farmers’ fields in 2007–2008 and 2008–2009 winter seasons, the addition of micronutrients and sulphur to wheat crops was used alongside the use of a common farmer practice, the use of farmyard manure (FM) and best practice inputs of N-fertilizer (150 kg N ha −1), P-fertilizer (26 kg P ha −1) and K-fertilizer (33 kg K ha −1). The application of FM with the recommended NPK treatment produced 9–13% more grain yield in the rice–wheat rotation when compared with the recommended NPK only treatment. Given that the farm sites used here had low levels of soil P, this may suggest that the recommended rate of 26 kg P ha −1 for the rice–wheat rotation is too low. The addition of FM did not improve any grain quality outcomes at any of the sites. There were no yield responses with S application with any of the rotations but the S input resulted in more wheat protein from all sites (average 8%). The addition of S also gave similar increases in grain hardness and the chapatti score. The inclusion of micronutrients (boron, copper, iron, zinc and manganese) with the recommended NPK treatment did not increase the grain yield at any of the sites when compared with the recommended NPK treatment, and sometimes, but not consistently, gave small responses with protein, grain hardness and chapatti score. In concurrent experiments wheat growth and chapatti quality were compared in zero till and conventionally sown systems, and with and without S fertilizer amendment. Here too there were no grain yield responses to S, and the protein, grain hardness and chapatti score were increased with S addition. Grain yields with zero till and conventional wheat were similar in the rice–wheat system and zero till sowing resulted in small increases in yield at all of the non-rice sites. The grain from the zero till treatments had higher protein (1–3%), grain hardness (3–10%) and chapatti score from all 4 rotations. Zero till has substantial adoption in the rice–wheat districts of Haryana but little farmer awareness and adoption in the areas where the other rotations are used. The data given here show that with zero tillage and an integrated practice of nutrient management farmers in Haryana can maintain grain yields of wheat whilst improving quality outcomes.

Irrigation and nitrogen scheduling as a requirement for optimising wheat yield and quality in Haryana, India

Wheat in Haryana (NW India) is grown as a winter crop in an annual sequence with rice, cotton, pearl millet or cluster bean as the main monsoon crops. Higher wheat yields in Haryana are associated with the use of modern varieties, increase in fertiliser use, improved irrigation practice and conservation tillage, and the recommendation to farmers for N fertiliser rates and timing and irrigation practice have an emphasis on optimising yield and input efficiencies. In India the importance to consumers of product quality does exist and, although the market place presently does not actively reward farmers for better quality wheat, the need for creating suitable and targeted marketing opportunities is now recognised. This paper examines aspects of input efficiencies and focuses on combinations of N-fertiliser and irrigation input in wheat crops grown with these four rotations (rice–wheat, cotton–wheat, pearl millet–wheat and cluster bean–wheat). Management practices that optimise grain production as well targeting grain that achieves best chapatti (Indian flat bread) quality are evaluated within a split-plot experiment where 4 irrigation schedule treatments were split with nitrogen management treatments involving a 2-way or 3-way split of N fertiliser. With the rice–wheat system, there were no differences between different split timings of N with grain yield, however with the 3 other wheat systems the 3 way split of N-fertiliser application, with N applied equally at N-fertiliser applied at seeding, early tillering and first node stage, always gave the highest yield. With all 4 rotations the highest protein level was achieved (range 11.8–12.5%) with this 3-way N application split. Grain yield increased in a step-wise manner as additional irrigation was implemented with all rotations and the highest protein outcomes were achieved with the least irrigations. The apparent recovery of N fertiliser applied was similar and highest with the 3-way split, and the 2-way split that did not include a basal N fertiliser application. Different rates of N fertiliser were included in separate experiments using the 3-way split of N application, and with the rice–wheat rotation the GreenSeeker instrument was used to establish the rate for the third application of N. The application of extra N-fertiliser with the non rice–wheat rotations produced no additional grain yield with an increase in the N-fertiliser input beyond 150 kg N ha −1, although protein and N-content increased incrementally. Grain hardness and chapatti score trended higher with increases in N-fertiliser input but the increases were relatively small. The use of the GreenSeeker instrument with the rice–wheat rotation resulted in N saving of 21–25 kg N ha −1 with similar grain yield, protein and grain hardness to that provided by using the recommended 150 kg N ha −1. Where the GreenSeeker was used the apparent recovery was 70–75% compared with 60% with the wheat receiving the recommended 150 kg N ha −1, suggesting farmers are likely to be over-fertilising their wheat crop. The best yields obtained in these experiments were about 5.5–6.0 t ha −1 and these yields are consistent with a decade-long attainable yield identified for wheat in rice–wheat rotation for Haryana. If farmers can achieve market recognition for chapatti quality, and with the use of appropriate varieties, then farmers can assume that the best practice outlined here for optimising grain yield with integrated nutrient and soil management will be the same practice that optimises chapatti quality.

Experiments on Specific Energy and Pulping Quality of Extrusion Mechanical Pulping

In order to select rational screw parameters for improving the pulping quality, efficiency and reducing specific energy, the paper studied the effects of the rotational speed of screw, lead number of reverse thread and slot width of reverse flight of the twin screw pulping extruder (TSPE) on specific energy, flux and pulping quality (reject rate, fiber length and fine component content) in the processes of extrusion mechanical pulping. The experimental results show that synthetically considering and pulping quality the efficiency, the screw rotational speed of 300 r/min–400 r/min is more appropriate. For poplar chips, the lead number should be greater than or equal to six. And for cotton stalks and wheat straws, the lead number should be no less than seven. For the combination screws of multiple extrusion zones, the slot width of the ultimate extrusion zone plays a decisive role on the fiber length. In addition, the slot width can also adjust the barrel pressure and the axial force of the screws. The work of the paper is significant for optimum design of the TSPE.

Improving irrigation water operation in the lower reaches of the Amu Darya River – current status and suggestions

AbstractIrrigated agriculture is widespread in the Central Asian drylands and important for food security of the region. However irrigation practices based on rules made for cotton production on large units do not provide adequate guidance for the now widespread small farms that produce cotton wheat and rice. Excessive unsustainable water use is the consequence. Land and water resource management practices were analysed in 2006 for the irrigated area (approx. 1885 ha) of a water users' association (WUA) as a case study. The Shomakhulum WUA is situated in the Khorezm region Uzbekistan in the Aral Sea Basin. The designed water allowance of 0.40 l s−1 ha−1 was 46% higher than the 0.21 l s−1 ha−1 required in 2006. A ponding experiment conducted at two locations under typically shallow groundwater conditions showed that actual seepage losses in the major distributing canal (Pakhtakiyar) in the WUA were about 2% at one site and negative at the other. This does not support the present blanket recommendation of an additional 29% of water to compensate for anticipated seepage losses. Considering the effects of shallow groundwater the seasonal leaching requirements were estimated at 200 mm versus the 400 mm based on the blanket local recommendations for a 14 ha cotton field. However the actually applied water amounted to 670 mm which exceeds the calculated requirements by 235% and the local recommendation by 68%. The findings showed (i) excessive irrigation water supply and in turn high wastage owing to an underestimation of the potential shallow groundwater contribution (ii) overestimation of conveyance losses and (iii) excessive leaching due to outdated knowledge on leaching requirements when compared to standards. We suggest that the outdated water allowance the inaccurate estimation of the conveyance efficiency and excessive water applications during leaching cause a waste of precious fresh water and a rise in the shallow groundwater levels which consequently increases secondary soil salinity. The revision of irrigation and leaching norms combined with an improved knowledge on seepage dynamics under shallow groundwater levels is needed before any further recommendations can be made to the farmers in order to reach the objective of sustainable agriculture in the area. Copyright © 2011 John Wiley & Sons Ltd.

Laying hen production and feeding practices in Togo: A survey

A survey was carried out, involving layer chicken farmers to identify and inventory the different feed components and to determine their rates of incorporation in poultry feed rations, as well as to inventory different layer lines or commercial crosses raised in Togo and finally to determine their production performances. During the survey, samples of feed ingredients and complete layer diets were collected for crude protein (CP) and gross energy (GE) levels determination. The survey indicated that 15 different feed components were used in the formulation of layer feed rations. Among these components, corn was the most important component (52.60±2.58%) followed by wheat bran (16.11±2.72%), roasted soya (11.40±1.91%), fish meal (8.29±1.64%) and cotton seed (7.57±1.58%). Rates of incorporation of these components in the feed ration varied according to the producer and the age of chickens, as there are no established standard requirements for layer feed in Togo currently. The survey revealed that average layer numbers per farm increased from 329 to 520 chickens between 2001 and 2005. Several layers strains or commercial crosses are present in Togo, however, only Isa Brown (IB), Harco and Hisex White (HW) were considered important. Productive performances were comparable between these three strains. It was concluded that promotion of the local egg industry in Togo should focus on the establishment of hatchery, proficient feed mill units, providing information about management practices and training those involved in the sector on appropriate technologies.

Effect of seeding rate on yield and yield components of durum wheat cultivars in cotton-wheat cropping system

This research was carried out in experimental field of Southeastern Anatolia Agricultural Research Institute in randomized split bloc design with three replications for three years (2004 - 2005, 2005 - 2006 and 2006 - 2007 growing seasons). The objective of this study was to determine the effects of seeding rates on grain yield and yield components of two durum wheat cultivars (Aydin-93 and Firat-93) under permanent bed planting in cotton–wheat cropping system. Six seeding rates (50, 150, 250, 350, 450 and 550 seed per m-2) were tested. Seeding rate affected grain yield and yield components except for protein content, but its effects is being altered from year to year. The results revealed that 253 seed per m-2 (111 kg ha-1) proved as predicted optimum seed rate; producing highest grain yield (5162 kg ha-1) as regards averages of all years. Among varieties, significant differences were found for yield and yield parameters. Key words: Chlorophyll content, durum wheat, grain yield, grain quality, seeding rate, permanent bed planting.

Soil water storage and drainage under cotton-based cropping systems in a furrow-irrigated Vertisol

Comparative studies of drainage and leaching under tillage systems in irrigated tropical and sub-tropical Vertisols are sparse. The objective of this study was to quantify drainage under cotton-based cropping systems sown on permanent beds in an irrigated Vertisol. Drainage and soil water storage were measured with the chloride mass balance method and neutron moisture meter, respectively, during the 2002�03, 2004�05, 2006�07 and 2008�09 cotton seasons in an on-going experiment in a Vertisol in NW NSW. The experimental treatments were: cotton monoculture sown either after conventional tillage or on permanent beds, and a cotton�wheat rotation on permanent beds where the wheat stubble was retained as in situ mulch into which the following cotton crop was sown. Subject to in-crop rainfall, irrigation frequency varied between 7 and 14 days for cotton and 2�3 months for wheat. In 2005, a split-plot design was superimposed on the existing experiment such that the main-plot treatments were irrigation frequency (�frequent�, 7�14-day irrigation interval; �infrequent�, 14�21-day irrigation interval), and sub-plot treatments were the historical tillage system/crop rotation combinations. In comparison with cotton monoculture sown either after conventional tillage or on permanent beds, soil water storage, particularly during the early part of growing season when rainfall provided the major proportion of crop water requirements, and drainage were greatest when a cotton�wheat rotation was sown on permanent beds. Seasonal drainage out of the 1.2 m depth, averaged among all seasons, was of the order of 25 mm, 33 mm and 70 mm with cotton monoculture sown either after conventional tillage or on permanent beds, and a cotton�wheat rotation on permanent beds, respectively. Soil water storage and drainage were also greater when irrigation frequency was greater. Seasonal drainage out of the 1.2 m depth, averaged between the 2006�07 and 2008�09 seasons, was 54 mm with �frequent irrigation�, and 28 mm with �infrequent� irrigation. Infiltration was less in management systems which resulted in wetter soil; viz. frequent irrigation or a cotton�wheat rotation on permanent beds with in situ stubble retention. Drainage water losses in a furrow-irrigated Vertisol may be reduced and soil water storage increased (i.e. water conservation improved) by sowing a cotton�wheat rotation with in situ stubble retention under less frequent irrigation

Tillage Effects on Soil Properties and Spatial Variability in Two Mississippi Delta Watersheds

Abstract This study evaluated changes in soil properties several years after implementation of conservation measures. Two approximately 50-ha fields within two Mississippi Delta oxbow lake watersheds (Deep Hollow and Beasley) were laid out in 60-m grids. Soil from a tilled cotton field in Deep Hollow watershed was sampled at each node in 1996 and again in 2000 after 4 years of reduced tillage cotton (Gossypium hirsutum) and winter wheat (Triticum aestivum L.) cover crops; soil also was collected from conventional tillage cotton in Beasley Lake watershed in 1996 and again in 2006 from the same grid nodes after 4 years of reduced tillage cotton and 5 years of reduced tillage soybeans. Organic matter levels in the soil surface were higher in both watersheds after conservation tillage was implemented, likely caused by increased plant residue accumulation and limited soil mixing. Higher soil P levels in both watersheds under conservation management were attributed to less distribution in soil because of reduced tillage. Lower NO3-N in Deep Hollow in 2000 suggested N immobilization in the soil surface. Nitrogen was not analyzed for Beasley soil samples. Soil pH values were also higher in the later samplings for both watersheds, but because lime was applied in the interim, it is difficult to ascribe an effect from tillage. Potassium, calcium, and magnesium were higher in 2000 after the 4-year reduced tillage practice in the Deep Hollow watershed. However, potassium, calcium, and magnesium were lower in 2006 than in 1996 at the Beasley Lake watershed because no fertilizer was applied to the field since 2001. Regardless of tillage system, relatively high P levels in soils from both watersheds are indicative of high native soil P levels in the Mississippi Delta soils. Similar to other studies, water-soluble P was positively correlated with Mehlich III P. Spatial relationships of P examined using kriging showed that P data were spatially dependent, and their spatial dependence was impacted by tillage practices.

Potential contribution by cotton roots to soil carbon stocks in irrigated Vertosols

The well-documented decline in soil organic carbon (SOC) stocks in Australian cotton (Gossypium hirsutum L.) growing Vertosols has been primarily analysed in terms of inputs from above-ground crop residues, with addition to soil C by root materials being little studied. Potential contribution by cotton roots to soil carbon stocks was evaluated between 2002 and 2008 in 2 ongoing long-term experiments near Narrabri, north-western New South Wales. Experiment 1 consisted of cotton monoculture sown either after conventional tillage or on permanent beds, and a cotton–wheat (Triticum aestivum L.) rotation on permanent beds; Experiment 2 consisted of 4 cotton-based rotation systems sown on permanent beds: cotton monoculture, cotton–vetch (Vicia villosa Roth.), cotton–wheat, and cotton–wheat–vetch. Roundup-Ready™ (genetically modified) cotton varieties were sown until 2005, and Bollgard™ II-Roundup Ready™-Flex™ varieties thereafter. Root growth in the surface 0.10 m was measured with the core-break method using 0.10-m-diameter cores. A subsample of these cores was used to evaluate relative root length and root C concentrations. Root growth in the 0.10–1.0 m depth was measured at 0.10-m depth intervals with a ‘Bartz’ BTC-2 minirhizotron video microscope and I-CAP image capture system (‘minirhizotron’). The video camera was inserted into clear, plastic acrylic minirhizotron tubes (50-mm-diameter) installed within each plot, 30° from the vertical. Root images were captured 4–5 times each season in 2 orientations, left and right side of each tube, adjacent to a furrow, at each time of measurement and the images analysed to estimate selected root growth indices. The indices evaluated were the length and number of live roots at each time of measurement, number of roots which changed length, number and length of roots which died (i.e. disappeared between times of measurement), new roots initiated between times of measurement, and net change in root numbers and length. These measurements were used to derive root C turnover between times of measurements, root C added to soil through intra-seasonal root death, C in roots remaining at end of season, and the sum of the last 2 indices: root C potentially available for addition to soil C stocks. Total seasonal cotton root C potentially available for addition to soil C stocks ranged between ~50 and 400 g/m2 (0.5 and 4 t/ha), with intra-seasonal root death contributing 25–70%. These values are ~10–60% of that contributed by above-ground crop residues. As soil organic carbon in irrigated Vertosols can range between 40 and 60 t/ha, it is unlikely that cotton roots will contribute significantly to soil carbon stocks in irrigated cotton farming systems. Seasonal root C was reduced by cotton monoculture, stress caused by high insect numbers, and sowing Bollgard II varieties; and increased by sowing non-Bollgard II varieties and wheat rotation crops. Permanent beds increased root C but leguminous rotation crops did not. Climatic factors such as cumulative day-degrees and seasonal rainfall were positively related to seasonal root C. Root C turnover was, in general, highest during later vegetative/early reproductive growth. Large variations in root C turnover and seasonal C indices occurred due to a combination of environmental, management and climatic factors.

Methane and nitrous oxide fluxes in annual and perennial land‐use systems of the irrigated areas in the Aral Sea Basin

AbstractLand use and agricultural practices can result in important contributions to the global source strength of atmospheric nitrous oxide (N2O) and methane (CH4). However, knowledge of gas flux from irrigated agriculture is very limited. From April 2005 to October 2006, a study was conducted in the Aral Sea Basin, Uzbekistan, to quantify and compare emissions of N2O and CH4 in various annual and perennial land‐use systems: irrigated cotton, winter wheat and rice crops, a poplar plantation and a natural Tugai (floodplain) forest. In the annual systems, average N2O emissions ranged from 10 to 150 μg N2O‐N m−2 h−1 with highest N2O emissions in the cotton fields, covering a similar range of previous studies from irrigated cropping systems. Emission factors (uncorrected for background emission), used to determine the fertilizer‐induced N2O emission as a percentage of N fertilizer applied, ranged from 0.2% to 2.6%. Seasonal variations in N2O emissions were principally controlled by fertilization and irrigation management. Pulses of N2O emissions occurred after concomitant N‐fertilizer application and irrigation. The unfertilized poplar plantation showed high N2O emissions over the entire study period (30 μg N2O‐N m−2 h−1), whereas only negligible fluxes of N2O (<2 μg N2O‐N m−2 h−1) occurred in the Tugai. Significant CH4 fluxes only were determined from the flooded rice field: Fluxes were low with mean flux rates of 32 mg CH4 m−2 day−1 and a low seasonal total of 35.2 kg CH4 ha−1. The global warming potential (GWP) of the N2O and CH4 fluxes was highest under rice and cotton, with seasonal changes between 500 and 3000 kg CO2 eq. ha−1. The biennial cotton–wheat–rice crop rotation commonly practiced in the region would average a GWP of 2500 kg CO2 eq. ha−1 yr−1. The analyses point out opportunities for reducing the GWP of these irrigated agricultural systems by (i) optimization of fertilization and irrigation practices and (ii) conversion of annual cropping systems into perennial forest plantations, especially on less profitable, marginal lands.

Effects of sowing date, tillage and residue management on productivity of cotton ( Gossypium hirsutum L.)–wheat ( Triticum aestivum L.) system in northwest India

In southwestern region of Punjab in north India, sowing dates of cotton crop in cotton ( Gossypium hirsutum L.)–wheat ( Triticum aestivum L.) system are staggered from last week of April to mid of May depending upon the surface water supply from canal as ground water is not fit for irrigation. Further, farmers practice intensive cultivation for seedbed preparation and burning of wheat straw before sowing of cotton crop. With the present farmers’ practices, yields have become static and system has become non-profitable. Field experiments were conducted on Entisols for two rotations of cotton–wheat system during the years of 2004–2005 and 2005–2006 in split plot design to study the direct and interactive effects of date of sowing and tillage-plus-wheat residue management practices on growth and yield of cotton and wheat and to increase the profitability by reducing the tillage operations, which costs about 50% of the sowing cost. The pooled analysis showed that in cotton crop, there was a significant interaction between year × dates of sowing. Among different tillage-plus-wheat residue management practices yields were 23–39% higher in tillage treatments than minimum-tillage. In wheat, grain yield in tillage treatments were at par. Water productivity amongst the tillage treatments in cotton was 19–27% less in minimum tillage than others tillage treatments. Similar trend was found in wheat crop. Remunerability of the cotton–wheat system was more with a combination of reduced tillage in cotton and minimum tillage in wheat than conventional tillage.