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India is the largest cotton-growing country (8.9 million hectares) in the world and most of the area is raindependent. Large amount of pesticides are used for the control of sucking pests and lepidopterans. Increasing demand for clean organic fibre has led to an interest in organic cotton. However, information on the effects of organic cultivation on fibre quality is limited. Seed cotton yield and fibre quality (length, strength, micronaire and uniformity) were determined for an organic and modern method of cultivation during 3 years (the end of year 11, soil samples were collected and analysed for soil organic carbon content, water-stable aggregates (%), and mean weight diameter. Averaged over 3 years, an additional 94 kg seed cotton ha )1 was produced in the organic over the modern method of cultivation and the difference was significant. The year · treatment interaction was significant. Seed cotton yield in the organic plots was significantly greater than the modern method of cultivation plots in 2003-2004 because of a well-distributed normal rainfall and low pest incidence. The main stem nodes 13-22 accounted for the largest numbers of bolls present on the plant. Plants of the organic plots had significantly (37-71 %) more bolls on nodes 13-27 than those for the plants of the modern method of cultivation. Lateral distribution of bolls on a sympodial (fruiting) branch, was noticed up to fruiting point 11. However, treatment differences were not significant. With regard to fibre quality (length, strength, fineness and uniformity), differences between years were significant. Inferior quality fibre was produced in 2004-2005 because of delayed planting and early cessation of rain. On average, cotton grown under organic conditions compared with the modern method of cultivation had significantly better fibre length (25.1 vs. 24.0 mm) and strength (18.8 vs. 17.9 g tex )1 ). Soil samples of the organic plots had significantly greater C content, water-stable aggregates and mean weight diameter than the modern method of cultivation plots. Differences were restricted to the top layers (0-0.1 and 0.1-0.2 m). Yield benefits of growing cotton in an organic system over the modern method of cultivation are expected to be greater in years receiving normal rainfall and having low pest incidence.

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Nutrient uptake and balance of the cotton (Gossypium hirsutum L.) + pigeonpea (Cajanus cajan(L.) Millsp.), a traditional strip intercropping system practiced on the rainfed Vertisols of central India is not known to us. On-farm participatory trials were conducted on 10 farmer fields, five each on medium deep (MDS) and deep soils (DS) of Nagpur, central India to determine the effect of technological interventions on N, P and K uptake of cotton and pigeonpea. The nutrient balance was also quantified as a difference of nutrient inputs and removal. Nutrients accumulated by the crops (grain, stalk and leaves) and weeds removed off the field by hand weeding were considered as nutrient removal, while fertilizer was considered as nutrient input. The interventions included application of recommended dose of fertilizer (RDF), RDF + conservation tillage with in situ green manure (CT 1 ) and CT 1 + application of ZnSO 4 (CT 2 ) and compared with farmers' practice (FP). Nutrient uptake, in general, was higher on DS than on MDS. Among the interventions, N, P and K uptake of cotton and pigeonpea followed the order: CT 2 > CT 1 > RDF > FP. Mean N and P balance was positive in all the treatments. The balance may become negative if nutrient losses are accounted. A negative K balance was observed in all the treatments and the magnitude was the greatest for the FP plots (À39.4 kg ha À1 y À1 ). In spite of fertilizer-K application in the intervention plots, K balance was negative (À14.4 to À19.5 kg ha À1 y À1 ). By way of leaf and fruit drop, cotton and pigeonpea litter recycled 12.2 kg N, 1.7 kg P and 6.7 kg K ha À1 y À1 .

The main objective of the study was to assess the soil nutrient status of two cotton (Gossypium hirsutum L.) cultivation systems (organic and modern method of cultivation) established in 1994. In general, the data indicate a depletion of the nutrient status with depth (0-0.1, 0.1-0.2, 0.2-0.3, 0.3-0.6, and 0.6-0.9 m). There was a significant build up of organic carbon (C) and nutrients, except iron (Fe) and magnesium (Mg), in the organic cultivation system (OCS) compared to the modern method of cultivation (MMC). Most of the accumulation was noticed in the top 0-0.3 m. The concentration of the mobile nutrient NO À 3 was significantly greater in the surface as well as in the deeper layers of the OCS plots than the MMC plots. Extractable P ORDER REPRINTS was 3.8-fold greater in the OCS than MMC plot in the top 0.1 m soil layer. At 0.3-0.6 m soil depth, it was 3-fold greater. Other immobile nutrients such as zinc (Zn), Fe, manganese (Mn), and copper (Cu) were also significantly greater in the 0.3-0.6 m depth in the OCS plots compared to the MMC plots possibly due to movement of enriched topsoil through the cracks following cultivations.

Conservation agriculture (CA) including reduced or no-tillage and crop residue retention, is known to be a self–sustainable system as well as an alternative to residue burning. The present study evaluated the effect of reduced tillage coupled with residue retention under different cropping systems on soil properties and crop yields in a Vertisol of a semiarid region of central India. Two tillage systems – conventional tillage (CT) with residue removed, and reduced tillage (RT) with residue retained – and six major cropping systems of this region were examined after 3 years of experimentation. Results demonstrated that soil moisture content, mean weight diameter, percent water stable aggregates (>0.25mm) for the 0–15cm soil layer were significantly (P<0.05) affected by tillage practices. Soil penetration resistance was significantly higher for RT than CT. Irrespective of soil depth, there was higher soil organic carbon (SOC) for RT than CT. The SOC fractions followed in the order: non-labile>moderately labile>less labile. At the 0–15cm depth, the contributions of moderately labile, less labile and non-labile C fractions to total organic C were 39.3%, 10.3% and 50.4% respectively in RT and corresponding values for CT were 38.9%, 11.7% and 49.4%. Significant differences in different C fractions were observed between RT and CT. Soil microbial biomass C concentration was significantly higher in RT than CT at 0–15cm depth. The maize–chickpea cropping system had significantly (P<0.05) higher soybean grain equivalent yield of 4.65 t ha–1 followed by soybean+pigeon pea (2:1) intercropping (3.50 t ha–1) and soybean–wheat cropping systems (2.97 t ha–1). Thus, CA practices could be sustainable management practices for improving soil health and crop yields of rainfed Vertisols in these semiarid regions.

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