Rainfed Cotton Research Articles

Effects of Diversification of Rainfed Cropping Systems to Enhance Sustained Yields for Semi-Arid Tropical Agroecosystems: Effects of 11–Years of Farmers’ Practice

Semi-arid tropical (SAT) soils cover approximately 11 million hectares (Mha) globally. Soils in SAT regions are prone to degradation if poorly managed, and approximately 38% of the developing countries’ poor who depend on these soils for their livelihood are at risk of malnutrition. Agronomic practices that can improve soil quality, and can sustain or improve crop productivity are critical for SAT agroecosystems. The objective of this study was to investigate the 11-year effects of farmer-imposed agronomic practices (cropping system and fertilization) on soil organic carbon (SOC), nitrogen (N), phosphorus (P), sulphur (S), and micronutrients [zinc (Zn) and boron (B)], and crop productivity in the Kothapally watershed, Andhra Pradesh, India. Rainfed diversified cropping systems with legumes in rotation or intercropping systems were compared with rainfed monoculture cotton systems. Soil samples were collected from each field of the participating twenty-three farmers in June 2010 and were compared with soil data collected in June 1999 from the same farmer’s fields. All soil samples were analyzed (with 10% replication) in the laboratory for physical and chemical characteristics using analysis of variance, where we tested the effects of crop (independent variable) on the dependent variables, e.g. SOC stocks, at p £ 0.05. Differences in the means were compared with a Tukey test. Relationships between SOC stocks and yield were evaluated with Pearson correlation analysis, and the sample size and correlation coefficients were reported when p £ 0.05. Increased SOC stocks were observed in rainfed diversified cropping systems with legumes in rotation or intercropping systems compared to rainfed monoculture cotton cropping system (p = 0.0283), and SOC stocks (in 2010) were correlated with 2010 crop yields (r = 0.384, n = 23, p £ 0.05). Overall, the 11-year study showed sustained crop productivity in rainfed diversified cropping systems compared to rainfed cotton cropping systems.

Long Term Effect of Tillage and Integrated Nutrient Management on Soil Quality and Productivity of Rainfed Cotton in Vertisols under Semi-Arid Conditions of Maharashtra

A field experiment was conducted to study the effect of integrated nutrient management in conventional and reduced tillage system on soil quality and productivity of rainfed cotton in Vertisols at Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola, Maharashtra. The experiment was carried out during 2005–06 to 2009–10 in Factorial Randomized Block Design with twelve treatment combinations and three replications. The treatments consisted of tillage (conventional and minimum), nutrient management viz., 100% RDF, 50% RDF with graded doses of farmyard manure (5, 10 and 15 t/ha) and in situ green manuring with dhaincha (Sesbania aculeata). The pooled results revealed that numerically higher seed cotton yield and sustainable yield index (SYI) was recorded in minimum tillage as compared to conventional tillage. The application of 50% RDF + FYM @ 15 t/ha recorded significantly higher seed cotton yield, SYI and soil quality index (SQI) alongwith significant improvement in physical, chemical and biological properties of Vertisols. However, application of FYM @ 10 t/ha along with 50% RDF also sustained the cotton productivity and was on par with application of FYM @ 15 t/ha + 50% RDF in respect of cotton productivity and soil fertility. Hence, it is recommended that the integrated application of FYM @ 10 t/ha along with 50% RDF was beneficial in improving soil quality and sustaining the rainfed cotton productivity in Vertisols under semi-arid conditions of Maharashtra.

Natural occurrence of entomopathogenic nematode species (Rhabditida: Steinernematidae and Heterorhabditidae) in cotton fields of Tamil Nadu, India

A total of 200 soil samples collected from the cotton fields of 10 different districts of the state of Tamil Nadu in India were evaluated for the presence of entomopathogenic nematodes (EPN) belonging to Steinernematidae and Heterorhabditidae during 2008–2009. This survey detected the occurrence of EPN in arable lands through the use of a standard insect baiting bioassay technique. EPN were recovered from all 10 cotton growing districts with 27 positive sites (13.5%) ranging from irrigated to rain-fed cotton fields of varied soil types (sandy to clayey), soil pH (4.9–8.4), electrical conductivity (0.11–1.25 dS/m) and organic matter content (0.21–3.8%). Both morphological and molecular tools were used to identify the isolates. Among 27 positive samples, 20 samples yielded steinernematids (74%) and seven samples yielded heterorhabditids (26%). The Heterorhabditis isolates were identified as Heterorhabditis bacteriophora. The Steinernema included Steinernema carpocapsae, Steinernema siamkayai and Steinernema monticolum. Steinernema carpocapsae was the predominant species. The cropping patterns comprising cotton–vegetables had higher EPN prevalence (26%) than cotton–pulses (22%), cotton–banana (3.3%) and cotton–millets (2.8%). Steinernema carpocapsae was recovered from cotton–pulses, cotton–millets and cotton–vegetables cropping patterns, whereas H. bacteriophora was isolated from cotton–pulses, cotton–vegetables and cotton–banana cropping patterns. This study demonstrated that EPN are prevalent in the cotton fields of Tamil Nadu, India and could potentially be incorporated into biological control or integrated pest management programmes.

Effect of different deficit-irrigation capabilities on cotton yield in the Tennessee Valley

Fluctuations in cotton (Gossypium hirsutum, L.) yield in the Tennessee Valley of Alabama are common and usually related to drought or irregular rainfall. A sprinkler irrigation study was established from 1999 to 2004 to evaluate the minimum design flow rate to produce optimum cotton yields and economic gain. A replicated randomized block design consisting of four irrigation treatments ranging from one inch every 12.5 days (equivalent to 1.5 gpm acre-1 design flow rate or system capability) to one inch every 3.1 days (6.0 gpm acre-1) and a control, rainfed treatment. Daily plant water requirement was determined using soil moisture sensors and a spreadsheet-based scheduling program (MOISCOT) developed by Alabama Cooperative Extension engineers. Significant yield differences between irrigated and rainfed cotton were noted during the study period, with rainfall variability and treatment effects accounting for most of the yield response. The minimum design flow rate (1.5 gpm acre-1) increased mean seed cotton yield by more than 500 lb acre-1 over rainfed yields. The most economically efficient design flow rate (4.5 gpm acre-1) increased mean seed cotton yield by more than 996 lb acre-1. A positive relationship was observed between cotton yield and total seasonal irrigation depth during dry years. Across all six years of the study, irrigated treatments produced significantly higher yields than rainfed cotton. The highest six-year cotton lint yield and net economic returns were obtained with the 4.5 gpm acre-1 irrigation treatment. This result provides a rule of thumb for estimating the extent of irrigated area based on available water supply rate.

Evaluating the Green Revolution after a decade: a Swaziland case study

This paper analyses the impact of the Komati Pilot Project (KPP) upon members and their neighbours. The KPP was a Government of Swaziland (GoS)-financed irrigation scheme that enabled 43 subsistence and semi-subsistence farmers to change from rain-fed maize and cotton to irrigated sugar cane. It provides an opportunity to evaluate the impact of Green Revolution technology upon an African rural community where adopters and non-adopters live close together and where little income differentiation existed prior to the development because the common experience was poverty. A baseline survey of the KPP was carried out in 1997 in advance of the Komati Downstream Development Project. Of concern are the extent and direction of any trickle-down effects from the KPP participants for their neighbours and the consequences of any such impacts 10 years after the project started producing sugar cane. The expectation of the GoS was that sugar cane would benefit KPP participants and neighbours creating a multiplier effect through increased demand for services and increased demand for agricultural labour. Ten years later, these expectations are unrealized.

ENSO-based climate variability affects water use efficiency of rainfed cotton grown in the southeastern USA

The El Niño Southern Oscillation (ENSO)-based climate variability can have a significant impact on crop production due to its effect on yield variation on space and time. The main objective of this study was to determine the impact of ENSO-based climate variability on water use efficiency (WUE) of rainfed cotton (Gossypium hirsutum L.) grown in the southeastern USA. Specific objectives were to determine the spatial and temporal variability of WUE of rainfed cotton as related to ENSO phases. The CSM-CROPGRO-Cotton model, previously calibrated and evaluated with observed data, was used to simulate seed yield and evapotranspiration of rainfed cotton for selected counties in Alabama, Florida, and Georgia for the period from 1950 to 2006. For each location, model simulations from nine planting dates were categorized into the ENSO phases using the Japan Meteorological Agency (JMA) index. Then, simulation outputs were used to calculate WUE as the ratio of cotton seed yield to crop evapotranspiration. For each location and planting date, normal values for WUE were obtained and deviations from normal for each ENSO phase were determined. Exploratory and nonparametric analyses were used to analyze the results. Our results suggest that WUE of rainfed cotton is differentially affected by ENSO. During El Niño years WUE deviations from normal tended to be negative for early planting dates but positive and larger for late planting dates, no tendency was found for the entire planting window during Neutral years. During La Niña years WUE deviations from normal tend to be positive and larger for early to mid planting dates, becoming smaller and negative for late planting dates. The stronger spatial dependence of WUE during La Niña years than during El Niño and Neutral years may imply that more attention should be given to planning strategies during La Niña years if we were to plan rainfed cotton in the region. Our results suggest that management practices of rainfed cotton tailored to ENSO-based climate variability are promising as a strategy for reducing the vulnerability of the crop to climate variability in the southeastern USA.

Radiation interception and conversion to biomass in two potassium-deficient cotton crops in South Benin

SUMMARYA potassium fertilizer field trial of rain-fed cotton crop was carried out on ferrasols at two sites in Benin. The measurements focused on leaf formation patterns and their ability to convert intercepted photosynthetically active radiation (PAR) into biomass. The results highlighted the role of K in plant architecture and leaf area development. On K deficient plots, the reduction in leaf area was mostly the result of a decreased number of leaves and, to a lesser extent, leaves of a smaller individual size. During vegetative growth, leaf senescence did not differ between treatments. Biomass partitioning to different plant compartments was found to be affected by potassium deficiency, in favour of leaves. No significant effect of K treatment was observed on the conversion of intercepted radiation into biomass.

Coccinellids and chrysopids as native predators of sucking pests in relation to rainfed cotton production system.

Status and dynamics of sucking pests (jassids ltnd aphids) and their native predators (coccinellids and chrysopids) were studied for five consecutive ycars (2001-05) in rainfed cotton production system. The effect of cultivars. cropping pattern, fertility levels and pest management options on the activity of predators was also inferred from the observations taken from differennt agronomic and plant protection field experiments. The range of jassid incidcnce, aphid infestation, activity of coccincllids and chrysopids was 2.4 to 7.5 nymphs per three leavcs, 15.0 to 38.9 percent, 0.1 to 0.4 and 0.52 to 1.87 per plant, respectively. Dynamics of the predators indicated perpetuating populaton of chrysopid over coccinellids with their association positive (r=0.058) but non-significant. Higher incidcnces of ,iassids and aphids and their predators were observed on the hybrids than the varieties. Long-term soil fertility changes did not have any direct influence on the predators. Significantly higher chrysopids and coccinellids (l.83 and 0.99 per plant) observed on cotton sole crop reduced the aphid infestation (19.2%) compared to the soybean-intercropped cotton (24.2%). While the occurrencc of coccinellids on cotton under protected and unprotected situations was discontinuous, chrysopids continued to occur betwccn August and November months. Recolonisation of both predators was observed under insecticidal spray situations. The paper discusses the role of coccinellids and chrysopids in the context of sucking pest management and emphasizes the need for designing cotton ecosystems favourable for higher predation by these native predators.

Viabilidade econômica de sistemas de preparo do solo e métodos de controle de Tiririca em algodoeiro

As plantas infestadas são responsáveis por perdas significativas na produção do algodão a nível mundial, cujo controle é difícil e oneroso. Com o objetivo de se estimar custos de produção e analisar economicamente a eficiência da plasticultura e de métodos de controle de ervas daninhas na cultura do algodoeiro herbáceo irrigado e em sequeiro, utilizaram-se dados obtidos de ensaios conduzidos nos municípios de Barbalha e Missão Velha, no Cariri Cearense, determinando-se o custo de produção, a receita líquida, o índice de lucratividade e os indicadores de viabilidade econômica: Valor Presente Líquido (VPL), Taxa Interna de Retorno (TIR) e Relação Benefício-Custo (B/C). Verificou-se que tanto no cultivo irrigado como no cultivo de sequeiro, o método de controle de ervas daninhas mais eficiente e bem menos oneroso, foi o mecânico com preparo do solo convencional, e mais lucrativo no cultivo de sequeiro, apresentando maior VPL e TIR que os demais. O maior custo de produção por hectare foi obtido no cultivo irrigado, utilizando-se o método e controle integrado em sistema de preparo do solo com aiveca. O uso da plasticultura como método de controle de ervas daninhas, é economicamente viável apenas para o cultivo do algodoeiro de sequeiro.

Row configuration as a tool for managing rain-fed cotton systems: review and simulation analysis

Rain-fed cotton production can be a significant proportion (average 17%) of the Australian Cotton Industry. One of the management techniques that rain-fed cotton growers have is to modify row configuration. Configurations that have entire rows missing from the sowing configuration are often referred to as ‘skip row’. Skip configurations are used to: increase the amount of soil water available for the crop, which can influence the potential lint yield; reduce the level of variability or risk associated with production; enhance fibre quality; and reduce input costs. Choosing the correct row configuration for a particular environment involves many, often complex, considerations. This paper presents an examination of how rain-fed cotton production in Australia is influenced by row configuration with different management and environmental factors. Data collated from field experiments and the cotton crop simulation model OZCOT, were used to explore the impact of agronomic decisions on potential lint yield and fibre quality and consequent economic benefit. Some key findings were: (i) soil water available at sowing did not increase the advantage of skip row relative to solid configurations; (ii) reduced row spacing (75 cm) did not alter lint yield significantly in skip row crops; (iii) skip row, rain-fed crops show reasonable plasticity in terms of optimum plant spacing within the row (simular to irrigated cotton); (iv) sowing time of rain-fed crops would appear to differ between solid and skip row arrangements; (v) skip row configurations markedly reduce the risk of price discounts due to short fibre or low micronaire and this should be carefully considered in the choice of row configuration; and (vi) skip configurations can also provide some savings in variable costs. In situations where rain-fed cotton sown in solid row configurations is subject to water stress that may affect lint yield or fibre quality, skip row configurations would be a preferential alternative to reduce risk of financial loss.

Effects of farmyard manure and fertilizers on yield, fibre quality and nutrient balance of rainfed cotton ( Gossypium hirsutum)

Two-year field experiments were conducted to evaluate the effect of fertilizer with or without farmyard manure (FYM) application on cotton productivity and fibre quality. A partial nutrient balance was calculated by the difference method (nutrient applied––crop removal). Seed cotton yield was improved with addition of FYM (5 Mg ha −1). Application of both N and P resulted in significant improvements in seed cotton yield than the control and without N plots (PK). Uniformity ratio and ginning outturn (GOT) was greater in the FYM amended plots than the plots without FYM. Nitrogen and P balance was positive in the fertilizer-N and P applied plots whereas K balance was negative in spite of the addition of fertilizer-K. Potassium balance was positive only when FYM was applied. These studies suggest that it is advantageous to apply FYM as it improves fibre yield by way of improved GOT and maintains a positive nutrient balance.

Evaluation of some pre- and post-emergence weed control measures on rain-fed cotton (Gossypium hirsutum L) in Nigerian savannah

The concept of season-long weed control has remained elusive in most cropping systems of the Nigerian savannah. Integration of pre-emergence herbicides with post-emergence weed control measures is likely to be the most viable option in this respect. Rainfed trials were conducted at Samaru, Nigeria in 1999, 2000 and 2001 seasons to evaluate the performance of some pre-emergence followed by post-emergence weed control treatments on cotton. Mechanical ridge moulding, hoe-weeding and fluazifop-butyl plus dimethametryne at 1.0 + 0.5 kg a.i./ha applied at 6 WAS reduced weed weight in two of the three trials. Fuazifop-butyl plus dimethametryne at 1.0 + 0.5 kg a.i./ha increased seed cotton yield in 1999 and 2000. Pre-emergence application of metolachlor plus fluometuron at 1.0 + 1.0 kg a.i./ha and mixtures of diuron with alachlor and metolachlor, each at 0.8 + 1.5 kg a.i./ha, reduced weed weight in two of the three trials; while weed cover score was depressed by all the treatments, except alachlor plus diuron at 1.5 + 0.8 kg a.i./ha and metolachlor plus terbutryne at 1.14 + 0.86 kg a.i./ha in 2000. Cotton stand count was depressed by alachlor plus diuron in 1999 and 2000. Metolachlor plus diuron at 1.5 + 0.8 kg a.i./ha, metolachlor plus fluometuron at 1.0 + 1.0 kg a.i./ha and metolachlor plus terbutryne at 1.14 + 0.86 kg a.i./ha increased plant height in two trials, while there was no consistent positive effect of any pre-emergence herbicide on bolls number and seed cotton yield. However, seed cotton yield was consistently higher (but not statistically higher) with metolachlor plus diuron, metolachlor plus fluometuron at 1.0 + 1.0 kg and metolachlor plus terbutryne at 1.14 + 0.86 kg a.i./ha than the weedy check.

Evaluation of some pre- and post-emergence weed control measures on rain-fed cotton ( Gossypium hirsutum L) in Nigerian savannah

The concept of season-long weed control has remained elusive in most cropping systems of the Nigerian savannah. Integration of pre-emergence herbicides with post-emergence weed control measures is likely to be the most viable option in this respect. Rainfed trials were conducted at Samaru, Nigeria in 1999, 2000 and 2001 seasons to evaluate the performance of some pre-emergence followed by post-emergence weed control treatments on cotton. Mechanical ridge moulding, hoe-weeding and fluazifop-butyl plus dimethametryne at 1.0 + 0.5 kg a.i./ha applied at 6 WAS reduced weed weight in two of the three trials. Fuazifop-butyl plus dimethametryne at 1.0 + 0.5 kg a.i./ha increased seed cotton yield in 1999 and 2000. Pre-emergence application of metolachlor plus fluometuron at 1.0 + 1.0 kg a.i./ha and mixtures of diuron with alachlor and metolachlor, each at 0.8 + 1.5 kg a.i./ha, reduced weed weight in two of the three trials; while weed cover score was depressed by all the treatments, except alachlor plus diuron at 1.5 + 0.8 kg a.i./ha and metolachlor plus terbutryne at 1.14 + 0.86 kg a.i./ha in 2000. Cotton stand count was depressed by alachlor plus diuron in 1999 and 2000. Metolachlor plus diuron at 1.5 + 0.8 kg a.i./ha, metolachlor plus fluometuron at 1.0 + 1.0 kg a.i./ha and metolachlor plus terbutryne at 1.14 + 0.86 kg a.i./ha increased plant height in two trials, while there was no consistent positive effect of any pre-emergence herbicide on bolls number and seed cotton yield. However, seed cotton yield was consistently higher (but not statistically higher) with metolachlor plus diuron, metolachlor plus fluometuron at 1.0 + 1.0 kg and metolachlor plus terbutryne at 1.14 + 0.86 kg a.i./ha than the weedy check.

Row configuration in rainfed cotton systems: modification of the OZCOT simulation model

Over the last 10 years, there has been a rapid expansion of rainfed cotton production in Australia. The majority of this area has used “skip row” configurations in which certain rows in the crop are not sown with the aim of providing a slowly available supply of soil moisture during periods of low rainfall. In the past, the OZCOT cotton crop simulation model has been used with long-term climate records to assess the impact of different management strategies for irrigated cotton production and to study the prospects for rainfed cotton production in the major cotton growing regions. In this paper, we present modifications made to OZCOT to better accommodate skip row. First, a simple procedure previously used to approximate light interception of row crops was assessed for its ability to enhance the capability of OZCOT to simulate skip row configurations and second, a modification to allow for the possibility that water in the skip is not as freely available as the water in the plant row was also explored. Including modifications to allow for differences in soil water extraction significantly improved predictions of crop yield for cotton in skip row configurations across a number of locations in the Eastern Australian cotton producing regions, but modifications to account for light interception in row configurations reduced the ability of the model to simulate skip row cotton yields. The modified model gave reasonable predictions of yield for solid planted and skip row crops. The performance was within the range of results published for solid planted crops over a range of nitrogen and irrigation treatments and planting dates. The model’s simulation of skip row yields when compared to solid planted crops grown under the same conditions, reflected the relationships seen in the measured data and those published in the industry literature.

Influence of tillage and residue management on growth and yield of cotton grown on a vertisol over 5 years in a semi-arid region of India

Inherent poor soil fertility is one of the factors responsible for the low productivity of rainfed cotton ( Gossypium hirsutum) grown on the vertisols of the Indian sub-continent. A conservation tillage system such as reduced tillage (RT) is one approach to improve soil conditions. Field studies were conducted over 5 years to evaluate RT systems and determine the effects of retaining cotton crop residues on growth and yield of cotton. Results indicated that the RT systems (RT1: two inter-row cultivations and RT2 with no inter-row cultivation) gave significantly greater seed cotton than the conventional tillage (CT) in the first 3 years. In the later 2 years, the differences were not significant. However, yield decline was noticed in RT2 where there was no soil disturbance due to the increased build up of dicot weeds. The effect of crop residue on seed cotton yield was significant in 1998–1999 and 2000–2001. Leaf amended (R1) and leaf+stalk amended (R3) yields were equal to the control (R0). Stalk alone amended (R2) plots had the least seed cotton yield. The RT plots, generally had greater plant dry matter and yield attributes (number of bolls per plant and seed cotton yield per plant) than CT plots during the first 3 years, which contributed to significant yield differences between RT and CT plots. Residue amended plots had significantly greater SOC than the control. Eliminating complete soil disturbance, as in RT2, may not be a viable option, because of increased weed density, especially dicot weeds. The RT1 comprising pre-plant herbicide application and one pass of harrow, and two inter-row cultivation for early season and late season weed control, respectively, is a viable option to cotton growers of the semi-arid tropics of India.

Standardize the dose and timing of defoliant application to facilitate synchronized maturity for mechanical harvesting of rainfed cotton (Gossypium hirsutum)

A field experiment was conducted at Regional Research Station, Aruppukottai, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu during the winter (rabi) season of 2016 and 2017 at Aruppukotai, Tamil Nadu, to study the influence of defoliants on SVPR 2 (Gossypium hirsutum L.) rainfed cotton. The experiment was laid out in randomized block design with 3 replication. The treatments consisted of defoliants spraying at different concentrations and time of application, viz. ethrel @ 1,500 ppm at 135 days after sowing DAS (D1), ethrel @ 2,000 ppm at 135 days after sowing (DAS) (D2), ethrel @ 2,500 ppm at 135 DAS (D3), ethrel @ 1,500 ppm at 150 DAS (D4), ethrel @ 2,000 ppm at 150 DAS (D5), ethrel @ 2,500 ppm at 150 DAS (D6), paraquat @ 1,500 ppm at 135 DAS (D7), paraquat @ 1,500 ppm at 150 DAS (D8) and control (D9). Observations, viz. growth parameters, yield-attributing characters and senescence parameters were recorded at 10 days after spraying and economics were worked out. The highest percentage of the senescence attributes, viz. percentage of of yellow leaves, yellow plants, dried leaves and leaf fall, was observed paraquat @ 1,500 ppm applied at 150 DAS. This was comparable with spraying of paraquat @ 1,500 ppm at 135 DAS and ethrel @ 2,500 ppm at 150 DAS during both years. Ethrel @ 2500 ppm at 150 DAS recorded the highest boll weight and more number of bolls/plant, resulting in significantly highest seed-cotton yield. The higher net income and the benefit: cost ratio were also recorded with the application of ethrel @ 2,500 ppm at 150 DA

Integrated weed management in rainfed cotton (Gossypium hirsutum L.)

A field experiment was conducted during the rainy season (kharif) 2000 to 2002 at Agriculture College farm, Nagpur, to find out suitable integrated method of weed control for rainfed cotton. Pre- and post-emergence appli- cation of herbicides along with 2 hand-weedings and 2 hoeings at 20 and 40 days after sowing (DAS) gave ef- fective control of weeds. The highest weed-control efficiency was recorded by pre-emergence application of pendimethalin followed by post-emergence application of glyphosate with 2 hand-weedings and 2 hoeings at 20 and 40 days. Maximum seed-cotton yield (8.54 qlha) was recorded with 3 hand-weedings and 3 hoeings fol- lowed by pre- and post-emergence application of pendimethalin and glyphosate with 2 hand-weedings and 2 hoeings (8.44 @ha). Maximum benefit : cost ratio (1.34) was recorded with 3 hand-weedings and 3 hoeings treatment. Among integrated weed-management treatments, the post-emergence application of glyphosate with 2 hand-weedings and 2 hoeings recorded more benefit : cost ratio compared to other integrated weed-manage- ment treatments.

Stress management in rainfed Bt. cotton (Gossypium hirsutum) through foliar sprays

In India, Bt cotton is grown on 122 Lakh ha area with production of 361 lakh bales and productivity is of 501 kg lint/ha. In Maharashtra it is grown on 41 lakh ha area with productivity of 81 lakh bales and productivity is 334 kg lint/ha. Cotton is grown on large scale under rainfed condition in Marathwada region of Maharashtra State and is a preferred cash crop in Kharif season by marginal as well as large farmers. The productivity of rainfed cotton par- ticularly in Marathwada region is uncertain due to occurrence of frequent dry spells particularly during July to Sep- tember. Hence to overcome the moisture stress under such dry spells condition and to obtain the sustainability in productivity, the measures like foliar application of potassium nitrate, water spray and other micronutrients are es- sential for reducing the rate of evapotranspiration. The experiment was conducted during 2017 to 2019 on experi- mental farm of All India Coordinated Research Project on Dryland Agriculture, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani. Study resulted that application of foliar spray of KNO (30 and 60 days after sowing) was 3 significantly superior in respect of increase in cotton yield as well as Net Returns as compared to the other treat- ments. Similarly, application of foliar spray during dry spell was also found superior than application of foliar spray after release of dry spells. The chlorophyll content, percent RWC and NDVI were also found higher under applica- tion of foliar spray which reflected in enhancing Bt. cotton productivity.

Effect of humic acid on rainfed upland cotton (Gossypium hirsutum)

Input cost is increasing day-by-day and it of water at squaring and flowering stages necessitates to develop low-cost technolo- (T,), foliar spray of 0.25% humic acid at gies for higher returns, especially in rainfed squaring aAd flowering stages (T,), foliar situation. Chandrasekaran (1989) reported spray of 0.5% humic acid at squaring and that soil application of humic acid as potas- flowering stages (T,), foliar spray of 1% sium humate might influence the crop humic acid at squaring and flowering stages growth indirectly through formation of com- (T,,), seed soaking in 0.5% humic acid and plexes with ammonium rendering the nitro- foliar spray of 0.5% humic acid at squaring gen slowly available and also through the - formation of complexes with iron and zinc Table 1. Effect of humic acid on growth and yield of rendering them absorbable by the plant rainfed upland conon roots. Seed soaking in 1.5% humic acid and foliar spraying of humic acid improve the Treatment Plant Sympodial Bolls1 Seed-cotton crop growth and yield in summer- height plant plant yield (cm) (ha) irrigated cotton (Gossypium sp.) (AICCIP, Coimbatore, 1994). There is limited infor- mation regarding the use of humic acid for rainfed cotton. Hence the present study was undertaken to find out the effect of humic acid treatment on seed-cotton yield of up- land cotton (G. hirsutum L.) under rainfed situation. A field experiment was conducted during the winter season (rabi) of 1991-92 at Kovilpatti, with 12 treatments in randomized block design replicated thrice. The treatments compared were the control (T,), application of farmyard manure @ 12.5 tonneslha (T,), seed soaking in water for 12 hr (T,), seed soaking in 0.5% humic acid for 12 hr (T,), seed soaking in 1% humic acid for 12 hr (T,), seed soaking in 1.5% humic acid for 12 hr (T,), foliar spray Details of treatment are described in text

Sustainable weed management programme for rainfed cotton based cropping system

Field experiments were conducted for two seasons (September '97 to April '98 and October 98 to May '99) at Fredrick Institute of Plant Protection and Toxicology (FIPPAT), Padappai, to develop a sustainable weed management programme in rainfed cotton. Results revealed that, intercropping of soybean and sesame led to weed suppression in rainfed cotton to the extent of 39.6 and 28.4 per cent respectively. The seed cotton yield obtained from cotton + soybean intercropping system under unweeded conditions was similar (1196 kg ha) to the yield of sole cotton supplenfented with single hand weeding alone (1220 kg ha¹). Similarly, single hand weeding operation in the cotton + soybean cropping system resulted in a substantially higher seed cotton yield (1528 kg ha-1), than the yield of sole cotton crop supplemented with two hand weedings (1432 kg ha¹). So, the adoption of Soybean, as a intercrop in rainfed cotton is an effective method for checking the weeds population as well as enhancing the yield potential in rainfed cotton and also labour saving, by minimising to one hand weeding. Similar effects were also found in cotton + sesame intercropping system. Furthermore, in labour scarce situation, the application of pre-emergence herbicide Fluchloralin @ 1.0 kg a.i ha in cotton-soybean intercropping system could be an alternative method.