Juri Buragohain

Crop diversification, crop and energy productivity under raised and sunken beds: results from a seven-year study in a high rainfall organic production system

Low productivity, crop diversification, employment and income are the major constraints of existing production systems of the high-rainfall north-eastern hill region (NEHR) of India. Field experiments were conducted for seven consecutive years to evaluate crop performance, production and energy balance of cropping sequences under raised and sunken bed (RSB) systems in mid-hills (950 m above mean sea level) of subtropical Meghalaya, India. Five vegetable-based cropping sequences on raised beds and six rice-based sequences on sunken beds were tested and compared with rice monocropping (control) under an organic production system. On raised beds, tomato–okra–French bean gave highest rice equivalent yield (REY; 44.7 t ha− 1) followed by carrot–okra–French bean (42.5 t ha− 1). Rice (cv. Shahsarang 1)-pea (cv. Prakash) gave highest REY (17.3 t ha− 1) on sunken beds. Among raised bed sequences, tomato–okra–French bean recorded greatest production efficiency (162 kg ha− 1 day− 1) and carrot–okra–French bean recorded highest land use efficiency (77%). Employment was enhanced by 187% with potato–okra–French bean and 181% with tomato–okra–French bean on raised beds, whereas rice–pea sequence on sunken beds enhanced employment by 62% over monocropping of rice. The energy productivity (energy output/input) was also higher with these cropping sequences. The adoption of RSB land configuration facilitated 244% cropping intensity (gross cultivated area/net cultivated area × 100) compared with 100% in rice monocropping. There was a significant improvement in soil chemical and biological parameters due to continuous organic production under RSB land configuration, indicating potential for organic farming in the subtropical hill ecosystem of India.

CONTINUOUS APPLICATION OF ORGANIC AMENDMENTS ENHANCES SOIL HEALTH, PRODUCE QUALITY AND SYSTEM PRODUCTIVITY OF VEGETABLE-BASED CROPPING SYSTEMS IN SUBTROPICAL EASTERN HIMALAYAS

SUMMARY The hill ecosystem of Northeastern Himalayas is suitable for organic farming due to negligible use of fertilizer (<12 kg ha −1 ) and agrochemicals, abundance of organic manure, especially plant biomass, and favourable climatic conditions for diverse crops. For successful organic farming, efficient cropping systems and organic amendments are to be identified to sustain soil health on one hand and productivity and enhanced income on the other. The efficacy of three organic amendments, namely, farmyard manure (FYM), vermicompost (VC) and integrated nutrient source (INS; 50% recommended dose of nitrogen (N) through FYM + 50% N through VC) on performance of three-vegetable-based cropping systems, namely, maize + soybean (2:2 intercropping)–tomato, maize + soybean–potato and maize + soybean– French bean was evaluated for five consecutive years (2005–06 to 2009–10) under subtropical climate at Umiam, Meghalaya, India (950 m above sea level). All the organic amendments were applied on N equivalent basis and phosphorus (P) requirement was compensated through rock phosphate. The results revealed that the yield of vegetables, except root vegetables, was maximum with FYM as soil amendment. Total system productivity in terms of maize equivalent yield (MEY) was significantly higher under FYM followed by INS. Pooled analysis revealed that MEY was enhanced by 200 and 191% with continuous application of FYM and INS, respectively, over control (no manure). Maize + soybean–tomato system recorded the highest MEY (28.78 Mg ha −1 ; Mg – megagram) followed by maize + soybean–French bean (24.37 Mg ha−1). INS as organic amendment resulted in maximum improvement in soil organic carbon (SOC), available P and potassium (K), soil microbial biomass carbon and water holding capacity and was similar to those under FYM. The SOC concentration under INS (23.6 g kg−1), FYM (23.3 g kg−1 )a nd VC (22.3 g kg −1 ) after five years of organic farming were 31.0, 29.4 and 23.8% higher than the initial and 26.2, 24.6 and 19.3% higher than those under control, respectively. The quality traits of tomato such as total soluble solids (5%), ascorbic acid (28.6 mg 100 g −1 ) and lycopene content (19.35 mg 100 g −1 ) were higher under FYM application than other amendments. The study indicated that FYM and INS are equally good as organic amendment and their continuous application not only improves soil health but also crop productivity. FYM application was also found to be cost effective as it resulted in a higher benefit: cost ratio (4.4:1) compared to other amendments irrespective of cropping sequences during transition to organic farming.

Impact of postburn jhum agriculture on soil carbon pools in the north-eastern Himalayan region of India

Land-use change, particularly soil organic carbon (SOC) loss induced by shifting cultivation (jhum) is a common land degradation issue in the hilly tracts of the humid tropics. The SOC concentration comprises different pools (labile and recalcitrant fractions), and each fraction responds to temporal dynamics of adopted management practices at varying magnitudes, such as deforestation followed by cultivation. However, information on the variation of different SOC pools due to cultural practices of vegetation burning and postburn agricultural practices (crop production) associated with shifting cultivation remains inadequate. In the present investigation, we examined the effect of burning and postburning cultivation on SOC pools across different forest fallow periods at Kolasib district, Mizoram state of the north-eastern Himalayan Region of India. Results revealed increase in the soil C stocks and total organic carbon (TOC) due to the increase in the length of fallow periods ranging from 3 to 23 years. The TOC decreased significantly compared with antecedent concentrations before vegetation burning. This was mostly attributed to the reduction in contribution of active pools (very labile and labile) to TOC from 69% to 60%. However, contribution of passive pools (less labile and nonlabile) to TOC concentration increased from 31% to 40%. Postburn cultivation also resulted in reduction of TOC as well as considerable variation in the proportion of different SOC pools to TOC concentration. Among the different pools of SOC, the very labile C pool was most sensitive to land-use change induced by shifting cultivation (phytomass burning and postburn cultivation). The labile SOC pools can act as a sensitive indicator for devising suitable location specific management practices for restoration of soil health through SOC dynamics in degraded jhum lands in hilly ecosystems.