Short Description of technology – General

China’s total organic fertilizer resources amount to over 70 million tonnes, with actual utilization being less than 40%. Among these, the nutrient return rate for livestock manure is around 50%, and the use of crop straw is about 35%. In greenhouse vegetable cultivation, the excessive use of chemical fertilizers with low nitrogen and phosphorus utilization has resulted in severe environmental issues and secondary salinization. Also, the on-going use of manures with low carbon-to-nitrogen ratios, to supply nitrogen (N), has contributed to low soil organic matter contents. There is also a general requirement for improved irrigation management.

The Institute of Agricultural Resources and Environment of the Hebei Academy of Agriculture and Forestry Sciences is addressing these production problems through long-term field trials (2009 to present, 2017 to present) with cucumber-tomato rotation. This research is examining an integrated technology system involving (1) the partial substitution of chemical fertilizers by organic fertilizers and straw, and (2) precise fertilizer and water management. The integrated technology system being developed will be suitable for different fertility conditions regarding soil organic matter and soil nitrogen and phosphorus supply.

Innovative Features

This integrated technology system, based on natural solutions, more effectively uses organic fertilizer resources and reduces the use of chemical fertilizers. It improves soil quality in greenhouses, enhances the efficiency of water and fertilizer use, and reduces nitrogen and phosphorus emissions. This enables appreciably more effective use of organic fertilizers and straw resources from animal husbandry and contributes to the sustainable use and green development of greenhouse vegetable production. The core of this technology is based on long-term multi-location experimental studies conducted to determine the nutrient requirements of vegetable crops in Hebei Province’s greenhouse vegetable production.

A simple and rapid method for recommending vegetable fertilizer rates has been developed that provides a high degree of control of nitrogen (N), phosphorus (P), and potassium (K) applications; with N applications being phased to crop growth. For most effective N management, the optimal organic-inorganic combination is that 40 to 50% of the N is supplied by organic fertilizers and straw. At the same time, the P and K application rate is based on the uptake of P and K and the fertility of the soil.

A smartphone-based “Fertilizer Calculator” APP has been developed. This technology has become the primary method for fertilizer and irrigation management for greenhouse vegetable production in Hebei Province, North China.

Type of Contribution

The determination of application coefficients that relate fertilizer application to crop nutrient uptake at different soil fertility levels is the core of this method. The application coefficients are related to soil fertility levels, which are classified as being high, medium or low. The values of these coefficients were determined based on the behavior of each nutrient in soil and through analysis of vegetable nutrient cycling characteristics. The application coefficient for N is based on a N balance calculation and is the ratio of N input to N output, where N input mainly includes applied fertilizer N + N supplied by irrigation and rain water + nitrogen brought by seeds, and N output mainly includes crop N uptake + nitrate leaching + ammonia volatilization + N₂O emissions. The N balance calculations were conducted for all the crops in the multi-location, long-term trials referred to previously. From those calculations, application coefficients for N that relate N fertilizer requirement to crop N uptake were derived for high, medium and low soil fertility levels. For P and K, the application coefficients are the ratios of input to output, which is fertilizer applied nutrient to crop nutrient uptake, for the different soil fertility levels. These were also derived from multi-location, long-term trials referred to previously.

For high-fertility soils (i.e. with relatively high levels of available nutrients), the application coefficients for N, P, and K are 1.05, 0.8, and 0.8, respectively. For low-fertility soils (i.e. with relatively low levels of available nutrients) where the objectives are to both increase yield and improve soil fertility, the application coefficients are higher, being 1.55,1.2, and 1.2, respectively. For medium-fertility soils, vegetable fields: the application coefficients for N, P and K are 1.35, 1.0 and 1.0, respectively.

The research on this technology conducted in long-term field trials showed that the optimal ratio of organic fertilizer to inorganic fertilizers for supplying N was 50:50, where the organic fertilizers were a mixture of manure and straw. Compared to conventional chemical fertilization, a 2 / 4 chemical fertilizer N + 1 / 4 pig manure N + 1 / 4 straw N treatment, appreciably reduced gaseous N losses by N₂O emission and by ammonia volatilization, and increased yield and biomass production.

This entire management system has been developed into an Android smartphone APP “Fertilizer Calculator” for vegetable production, which allows farmers to simply input information about crop rotation, yield, and soil fertility in order to receive recommended fertilizer rates and irrigation management plans. Numerous high-level scientific papers have been published on how this technology enhances soil organic matter, active soil organic carbon, and soil biological activity when using organic fertilizers combined with straw to replace 50% N of chemical fertilizers.

Benefits for farmers, the industry, and the environment

As a key agricultural technology throughout Hebei Province, this technology offers significant economic and ecological benefits. The application of this technology has resulted in an average increase of 6.5% in vegetable yields compared to conventional farming practices. The average reductions in chemical fertilizer use were 29% for N, 7% for P, and 3% for K.