Application of Climatic Productivity in the Analysis of Vegetable Yield

[Objective] Climatic productivity was applied to forecast and analyse the vegetable yield. [Method] Climatic productivity model presented by Zhou and the long-range climate forecasting method were adopted to analyse characteristics of the change of climatic productivity potential at Beibei District in combination with the ac- tual vegetable yield. [Result] The change of climatic productivity at Beibei District was fluctuant in an stable overall trend. The difference of spatial distribution of cli- matic productivity was apparent, with high climatic productivity potential in the north- east; in the actual production, vegetable yield was declining and it was the same with the climate use efficiency; according to the prediction, the vegetable yield would increase slightly in the future 10 years. [Conclusion] This study provides bases for the reasonable plan and layout of vegetable plantation under the climatic condition at Beibei District, as well as the selection of vegetable cultivars.

Effect of N and K Fertilizers on Yield and Quality of Greenhouse Vegetable Crops

The application of large amounts of fertilizers, a conventional practice in northern China for the production of vegetable crops, generally leads to substantial accumulation of soil nutrients within a relatively short period of time. A fixed field experiment was designed to study the effects of nitrogen （N） and potassium （K） fertilizers applied to optimize the yield and quality of typical vegetable crops. Application of N and K fertilizers significantly increased the yields of kidney bean. The largest yields were obtained in the first and second years after application of 1 500 kg N and 300 kg K20 ha^-1. In the third year, however, there was a general decline in yields. Maximum yields occurred when intermediate rates of N and K （750 kg N and 300 kg K20 ha 1） were applied. However, no significant differences were observed in the concentrations of vitamin C （VC） in kidney bean among different years and various rates of fertilizer treatments. Yields of tomato grown in rotation after kidney bean showed significant responses to the application of N and K in the first year. In the second year, the yields of tomato were much lower. This suggested that the application of N fertilizer did not have any effect upon tomato yield, whereas application of K fertilizer did increase the yield. Application of K fertilizer was often associated with increased sugar concentrations.

Biochar can Increase Chinese Cabbage(Brassica oleracea L.)Yield,Decrease Nitrogen and Phosphorus Leaching Losses in Intensive Vegetable Soil

There are few evidences on the effect of biochar on vegetable yield,nitrogen(N)and phosphorus(P)leaching losses under intensive vegetable production soil.The current field plot scale study evaluated responses of Chinese cabbage(Brassica oleracea L.)yield,N and P leaching losses using five N treatments of common N application rate according to local farmers’practice(N100%),reducing 20%or 40%N fertilizer(N80%and N60%),and reducing 40%N fertilizer but incorporating 10 or 20 t/ha biochar(N60%+BC10 and N60%+BC20).Results showed that N80%and N60%decreased both the cabbage economic and leaf yields by 6.8%-36.3%and 27.4%-37.7%,respectively.Incorporation of biochar with reduced N fertilizer rates improved the cabbage yield,in particular the N60%+BC20 matched the yield that observed in N100%treatment.Enhanced N and P uptake capacities of cabbage shoot probably contributed the higher vegetable production under both biochar amendment schemes.Biochar application mitigated the NH_(4)^(+)-N and total P leaching losses by 20%-30%and 29%-32%,respectively,compared with their counterpart treatment N60%.Nevertheless,biochar exerted no influence on the NO_(3)^(-)-N leaching.In addition,soil organic matter content was recorded with 7.4%-28.7%higher following 10-20 t/ha biochar application.In conclusion,biochar application can increase economic yield of cabbage via increasing N and P use efficiency,decrease N and P leaching losses,and improve soil quality in an intensive vegetable production system.

Responses of vegetation yield to precipitation and reference evapotranspiration in a desert steppe in Inner Mongolia,China

Drought,which restricts the sustainable development of agriculture,ecological health,and social economy,is affected by a variety of factors.It is widely accepted that a single variable cannot fully reflect the characteristics of drought events.Studying precipitation,reference evapotranspiration(ET_(0)),and vegetation yield can derive information to help conserve water resources in grassland ecosystems in arid and semi-arid regions.In this study,the interactions of precipitation,ET_(0),and vegetation yield in Darhan Muminggan Joint Banner(DMJB),a desert steppe in Inner Mongolia Autonomous Region,China were explored using two-dimensional(2D)and three-dimensional(3D)joint distribution models.Three types of Copula functions were applied to quantitatively analyze the joint distribution probability of different combinations of precipitation,ET_(0),and vegetation yield.For the precipitation–ET_(0)dry–wet type,the 2D joint distribution probability with precipitation≤245.69 mm/a or ET_(0)≥959.20 mm/a in DMJB was approximately 0.60,while the joint distribution probability with precipitation≤245.69 mm/a and ET_(0)≥959.20 mm/a was approximately 0.20.Correspondingly,the joint return period that at least one of the two events(precipitation was dry or ET_(0)was wet)occurred was 2 a,and the co-occurrence return period that both events(precipitation was dry and ET_(0)was wet)occurred was 5 a.Under this condition,the interval between dry and wet events would be short,the water supply and demand were unbalanced,and the water demand of vegetation would not be met.In addition,when precipitation remained stable and ET_(0)increased,the 3D joint distribution probability that vegetation yield would decrease due to water shortage in the precipitation–ET_(0)dry–wet years could reach up to 0.60–0.70.In future work,irrigation activities and water allocation criteria need to be implemented to increase vegetation yield and the safety of water resources in the desert steppe of Inner Mongolia.

Effects of N Forms and Rates on Vegetable Growth and Nitrate Accumulation

Experiments were carried out on a vegetable field with Peking cabbage(Brassica pekinensis (Lour.) Rupr.), cabbage (Brassica, chinensis var. oleifcra Makino and nemoto),green cabbage (Brassica chinensis L.), spinach (Spinacia oleracea L.) and rape(Brassica campestrisL.) to study the effects of N forms and N rates on their growth and nitrate accumulation. Theresults indicated that application of ammonium chloride, ammonium nitrate, sodium nitrate and ureasignificantly increased the yields and nitrate concentrations of Peking cabbage and spinach.Although no significant difference was found in the yields after application of the 4 N forms,nitrate N increased nitrate accumulation in vegetables much more than ammonium N. The vegetableyields were not increased continuously with N rate increase, and oversupply of N reduced the plantgrowth, leading to a yield decline. This trend was also true for nitrate concentrations in somevegetables and at some sampling times. However, as a whole, the nitrate concentrations in vegetableswere positively correlated with N rates. Thus, addition of N fertilizer to soil was the major causefor increases in nitrate concentrations in vegetables. Nitrate concentrations were much higher inroots, stems and petioles than in blades at any N rate.