No abstract

In the south of the Tibet Autonomous Region of China there is a network of valleys where intensive agriculture is practiced. Although considered highly productive by Tibetans, farm incomes in the region are low, leading to a range of government initiatives to boost grain and fodder production. However, there is limited information available on current farming practices, yields, and likely yield constraints. The present paper uses available data and farmer interviews to describe the agro-climate and current systems of crop and livestock production, and considers possible strategies to boost production. Although winters in Tibet are cold and dry, summer and autumn provide ideal conditions for crop growth. Cropping systems are characterised by heavy tillage, frequent irrigation, high seeding rates and fertiliser applications, some use of herbicides, and little stubble retention or mechanisation. Spring barley and winter wheat are the predominant crops, followed by rapeseed, winter barley, and minor fodder and vegetable crops. Average yields for the main grain crops are around 4.0 t/ha for spring barley and 4.5 t/ha for winter wheat, significantly lower than should be possible in the environment. Farmers typically keep five or six cattle tethered near the household. Cattle are fed diets based on crop residues but are generally malnourished and rarely produce beyond the needs of the family. It is suggested that research and extension in the areas of crop nutrition, weed control, irrigation, seeding technology, and crop varieties should enable significant increases in grain yield. Increases in cattle production will require increases in the supply of good quality fodder. Cereal/fodder intercrops or double crops sown using no-till seed drills might enable the production of useful amounts of fodder in many areas without jeopardising food grain supply, and allow more crop residues to be retained in fields for improved soil health.

This study evaluates the response of maize growing cycle length to meteorological variables at regional scale particularly, in the short-term period, considering global climate change. The experiment was carried out in Veneto Region (Northeast Italy) where maize phenological data collected by the regional network from 2005 to 2007 were combined with temperature data to analyse the relationship between BBCH stages and thermal sum. The effects of climatic changes in the near and medium term on maize phenology and on water requirements were also evaluated over a grid of climatic data obtained from different climatic models. The piecewise analysis gave the best fitting between BBCH and Growing Degree Days observed data characterized by two lines with different slopes with BBCH 70 (beginning of fruit development) as changing stage. The angular coefficient of the first line was 2.6 times than the second one (0.028) suggesting that the early stages of the growing cycle are more sensitive to air temperature. The simulation of maize phenology evolution highlights a modest variation at the 2020-time horizon, while an expected reduction of maize growing cycle of about 10 days has been estimated for 2030-time horizon. Long-term phenological observation are desirable to confirm our findings and to improve the strength of dataset.