Soil properties related to land-use systems in oases of Sangong river watershed, Xinjiang

Understanding the effect of human activities on the soil environment is fundamental to understanding global change and sustainable development. In the process of transformation of tropical rain forests and semiarid grasslands to farmlands, land degradation usually occurs. But the transformation of arid desert landscape to oasis is found to have quite different consequences. Taking an alluvial plain oasis in the north piedmont of the Tianshan Mountains as a case study, we investigate oasis soil properties related to different land-use systems during the transformation of arid desert to oases. Selected land-use systems con- sisted of an annual crop field less than 3 years old, annual crop field 3-6 years old, annual crop field more than 6 years old, perennial crop field less than 4 years old, perennial crop field of 4-6 years old, perennial crop field more than 6 years old, abandoned farmland more than 3 years old, woodland field more than 6 years old, ecological forestation field, natural shrubbery field, desert grass land, and saline or alkaline field. Different land-use systems affect significantly the distribution of sand, silt and clay. Sand content in oasis soil tends to decrease with cultivation years but silt and clay contents tend to be increased in the oasis soils. Soil fertility is higher in the land-use systems under strong human disturbance than under weak human disturbance. Oasis soil nutrients also tend to increase with cultivation years. Soils have a significantly lower salinity in the land-use systems under strong human disturbance than under weak human disturbance. Soil organic matter and nutrients of the annual and perennial crop systems in the oasis tend to increase with cultivation time with the oasis soil acting as a carbon sink. These results show that soils are not degraded and the soil quality is gradually improved under rational land use and scientific management patterns, including uniform exploitation of land resources, effective irrigation systems, sound drainage systems, balanced fertilizer application, crushed straw return to soil and transformation of annual crop fields to perennial ones.

Food resource and temporal partitioning amongst a guild of predatory agroecosystem-inhabiting ant species

Prey diversity and temporal foraging patterns of six abundant,predatory ant species were investigated seasonally in an agroecosystem with two main vegetable crops.Pheidole sp.demonstrated the highest predation success and therefore appears to be the dominant species while Tapinoma melanocephalum showed the lowest success under the natural field conditions.Investigation of prey diversity and temporal activity patterns with the null model tests of niche overlap revealed a significant overlap indicating that the activity periods and prey diversity may not be solely influenced by interactions among the co-existing ant species.However,niche partitioning in the daily peak activity periods was demonstrated during all the three seasons(summer,rainy and winter)particularly between Pheidole sp.and T.melanocephalum.Pheidole sp.exhibited a high intensity,broadly extended mono-modal foraging pattern.Camponotus compressus and C.paria showed bi-modality in their foraging activity during the rainy season and mono-modal patterns during summer and winter seasons.Pachycondyla tesserinoda,Tetramorium sp.and T.melanocephalum exhibited peak foraging activities in the morning hours during the summer and rainy seasons.The activity profiles of C.compressus and T.melanocephalum were skewed towards late afternoon hours during the winter season indicating avoidance of foraging activity during the favourable periods when the more aggressive Pheidole sp.is active.In the sponge gourd agroecosystem,the ants captured predominantly hymenopteran,orthopteran and coleopteran insects.While Pheidole sp.hunted mainly the large orthopteran prey,other ant species captured worker ants in the sponge gourd agroecosystem.In the cauliflower agroecosystem,while other species captured prey chiefly belonging to six orders,i.e.,Lepidoptera,Hymenoptera,Coleoptera,Hemiptera,Isoptera and Diptera,Pheidole sp.and P.tesserinoda were the only species to also hunt many orthopteran prey.The agroecosystem-inhabiting ant species prey on a large number and wide variety of insect herbivores as evident from the differences in the peak foraging times and the proportion of each type of prey hunted.Overall,our results indicate that the structure of agroecosystem-inhabiting ant assemblage may be influenced by a variety of factors including competition,temporal heterogeneities,prey availability and its characteristics such as size and mobility.

Performance of no-till corn precision planter equipped with row cleaners

In the continuous annual wheat-corn cropping area of North China Plain,no-till planting that promotes soil conservation and crop yield while reducing operation cost has been gradually accepted by local farmers.However,previous wheat residue is the main limiting factor affecting the performance of existing planters in placing seeds at uniform spacing and optimum depth in residue covered fields.In order to solve this problem,a kind of ground-wheel-driven row cleaner was designed,developed and mounted on row units of a four-row pneumatic precision planter.The planter has two adjacent row units equipped with the newly designed row cleaners and the other two adjacent row units equipped with the commonly used inactive row cleaners.This was used for planting at three forward speeds(4 km/h,6 km/h and 8 km/h)into half residue(HR)and whole residue(WR)plots.The amount of residue removal,seeding depth,emergence rate and indices of uniformity in seed spacing(missing-seeding index,quality of feeding index and precision index)were measured.The newly designed row cleaner performed better with regard to residue removal,with the average percentage of residue cleared as 63.0%compared to 40.3%for the inactive row cleaner.For the HR and WR plots,percentage of residue cleared of the newly designed row cleaner reached 57.1%and 68.9%respectively,suggesting that the newly designed row cleaner can work more effectively at high residue level.By contrast,with the percentage of residue cleared of the inactive row cleaner as 43.1%and 37.5%in HR and WR plots,suggesting that the inactive row cleaner just can work effectively under low residue condition.Values of missing-seeding index,QFI,precision index,coefficient of variation of depth and percent emergence for the newly designed row cleaner under whole residue level are comparable to those for the inactive row cleaner under half residue level.The result indicates that the effect of using the newly designed row cleaner is equal to that of reducing surface residue,and can help to maintain the uniformity of seed spacing and seeding depth.The newly designed row cleaner generally performed better at forward speed of 6 km/h,based on the distribution of seeds along rows and seeding depth uniformity.