Indian agriculture is highly dependent on monsoon rains and its vagaries still play havoc with it. The agriculture year starts on June 1 and ends with May 31 of the next calendar year. In between it has two cropping seasons: One, Khariffcrops grown under summer monsoon and harvested in autumn or early winter; and, two, Rabicrops grown in post-monsoon season (October-November) and harvested in the early spring. The rabi crops are grown under the stored soil moisture that has been provided by summer monsoon rains. In other words, heavy precipitation under summer monsoon has an impact on crop production in the rabi season.

Against this backdrop, the authors B Preethi and J V Revadekar , of the first paper, "Impact of Summer Monsoon Precipitation on Winter Crop Yields Across India", have made an attempt to analyze the impact of the frequencies of moderate to heavy precipitation events under summer monsoon on the crop yields in rabi season. The study revealed that the crop yield during rabi season is strongly correlated with the variation in frequencies of various fixed threshold values of rainfall during summer monsoonexcess rain resulting in high yields, while drought in summer monsoon period resulting in reduced yields. However, spatial coverage varied from threshold to thresholdwith increased threshold value of rainfall, regions with positive correlation coefficients had decreased. More than the total precipitation during summer monsoon, it is the number of rainy days that had positively impacted the crop yieldsyield precipitation response curves have shown increased yield with increased frequency of rainfall. As the authors opined, the scope of the study, however, needs to be widened by taking all the weather and non-weather parameters that are known to impact crop yields for a reliable prediction of rabi yields.

In the next paper, "Soil Fertility and Plant Diversity in Sabal Forest Reserve, Borneo", Hashim N R studied the impact of anthropogenic disturbances on the soil fertility status along with composition of plant species in two different forest types in Borneo. The study revealed severe habitat degradation due to prior land use in the forest reserve. In terms of plant abundance and richness, the `logged-over' forest zones were dominated by small trees, whereas the understorey was composed of dense ferns and sedges. The author is, therefore, of the opinion that to encourage species richness and abundance in the tree plantations, authorities associated with forest management must take note of the high susceptibility soils to anthropogenic disturbances.

As nitrogenous fertilizers are subjected to several transformation losses in the rice ecosystem, `Nitrogen Use Efficiency (NUE)' continues to attract the attention of soil scientists. Against this backdrop, the authors, M Z Hussain, Shakeel A Khan, and T M Thiyagarajan, of the next paper, "Increasing Nitrogen Use Efficiency in Rice (Oryza sativa L.) with Chlorophyll Meter and Leaf Color Chart", have conducted field experiments during 1998-99 to arrive at an efficient N management system based on the leaf N status of rice plant using two cultivarsADT 36 and ASD 19. The findings revealed that application of N based on chlorophyll measurement using SPAD meter at 14 days interval or at the critical growth stages of active tillering, panicle initiation, and 10 days after panicle initiation would save 40-50% of N as compared to blanket recommendations. However, taking into consideration the cost of chlorophyll meters (SPAD meter), the authors suggest usage of Leaf Color Chart (LCC) by small farmers, though not as efficient as SPAD meter. The study also reveals that application of polymer coated N fertilizer saves 40% of N fertilizer vis-à-vis the blanket recommendation.

The authors, Amarjeet, S S Punia and Ashok Yadav, of the paper "Residual Phytotoxicity of Chlorsulfuron Applied in Wheat (Triticum aestivum L.) on Succeeding Crop of Maize (Zea mays L.)", have evaluated the phytotoxic effect of chlorsulfuron applied to control weeds in wheat crop under different irrigation schedules, on the subsequently grown maize crop. Based on their findings, the authors opine that chlorsulfuron @ 20-30 g ha^_1 satisfactorily controlled weeds in wheat crop, but it is not advisable to grow maize following wheat in the fields where chlorsulfuron is applied.

In the next paper, "Rainwater Harvesting and Management Technology for New Livelihood of Submontane N-W Tract Zone Farmers of India", the authors, M S Hadda and Sanjay Arora, described various economically viable and easily adaptable rainwater harvesting techniquescost of preparation, size and capacity of water harvesting tanks, water loss, lining material usage, water productivity and the diversified uses of stored waterthat are well-suited for farmers of N-W zone of India, where precipitation rate varies from 850-1,100 mm and yet faces scarcity of water during winter season. It also discusses about the future strategies for adoption in the zone.

The last paper, "Sediment Observation in River Basins: A Case Study", by B K Purandara and A V Shivapur, presents the findings of the study carried out on sedimentation process in the river Pamba, which reveals that the sediments in the river are mainly transported as graded suspension, more by the bottom turbulence.

-- GRK Murty
Consulting Editor