Abstract: 【Objective】This research was conducted to explore the effect of different year-round management models of combined application of nitrogen (N), phosphorus (P) and potassium (K) nutrients on grain yields and nutrient efficiency of wheat-maize rotation system in lime concretion black soil and identify an optimal model for the use efficiency of the combined N, P, and K fertilizers in integrated wheat and maize planting system in the lime concretion black soil in the southeast area of Henan province.【Method】A field experiment of combined application of N, P, and K fertilizers was persistently performed in a typical lime concretion black soil area located in Shangshui country, Zhoukou city of Henan province during two continuous wheat-maize growing seasons (2012.09-2013.08 and 2013.09-2014.08). In this experiment, a wheat-maize rotation system was designed, in which the amounts of total P and K fertilizers were not changed while two different amounts of N fertilizers and different application methods of P and K fertilizers were applied. And the effects of this rotation on absorbance and utilization of N, P, and K fertilizers by wheat and maize crops were studies. In this study, two different amounts of N fertilizers were applied at two levels of 360.00 kg·hm^-2 and 540.00 kg·hm^-2 in every year. The amounts of total P and K fertilizers were not changed, whereas these two fertilizers were applied with four different ways: all P and K fertilizers were applied in wheat and maize growing seasons, respectively; all P fertilizers were applied in wheat growing seasons, and K fertilizers were applied in both wheat and maize seasons and the ratio of K fertilizer applied in these two seasons was 42:58; all K fertilizers were applied at maize growing season and P fertilizers were applied in both wheat and maize seasons with 64:36 ratio for these two crops; P and K fertilizers were simultaneously applied into soil in both wheat and maize seasons and the ratios of P and K fertilizers applied in these two seasons were 64:36 and 42:58, respectively. The aim of this study is to find an optimal combined mode of application of N, P and K fertilizers in wheat/maize rotation system in the lime concretion black soil.【Result】Results of the experiment indicated that under large amount of the applied N fertilizer condition, simultaneous application of P and K fertilizers in both wheat and maize crops could promote the coordinated development of three key components of wheat and maize yields, and significantly improved the spike number of wheat and the lengths as well as row grains of maize spikes. Of all treatments in these two continuous crop growing seasons, P8 treatment (a larger amount of P fertilizer applied to wheat and a larger amount of K fertilizer applied to maize) harvested the highest grain yields in both a single or two seasons, and year-round yields were respectively 21 274.2 kg·hm^-2 and 20 219.1 kg·hm^-2 in two growing seasons (2012.09-2013.08 and 2013.09-2014.08). The nutrient contents in aboveground tissues of wheat and maize crops showed N>K>P in lime concretion black soil. Compared with low amounts of the applied N fertilizer condition, large amounts of the applied N fertilizers were helpful to improvement of the contents of total N, P and K nutrients in the aboveground tissues of these two crops, whereas reduced nitrogen partial factor productivity (NPFP), nitrogen uptake efficiency (NUPE) and nitrogen use efficiency (NUE). Simultaneous application of P and K fertilizers to both wheat and maize crops in one growing year improved the absorbance of N fertilizers, prevented the loss of major nutrients, improved the absorption and utilization of P and K fertilizers of both wheat and maize crops, and significantly increased partial productivity (PFP) and uptake efficiency (UPE) of P and K fertilizers. However, application of total P or K fertilizers in single wheat or maize resulted in the reduced use efficiency of major nutrients and the decreased yields of the subsequently planted crops for unbalanced nutrient supply and the reduced absorbance of N, P and K fertilizers, because P fertilizer is easily immobilized into soil and K fertilizer is easily washed away from soil, respectively. The yield of subsequently planted crops would decrease in this way, because the crops could not absorb and utilize N, P and K in the soil environment of unbalanced nutrient supply. Under small amount of the applied N fertilizer condition, absorbance and utilization of N, P and K nutrients in P4 treatment (a larger amount of P fertilizer applied to wheat and a larger amount of K fertilizer applied to maize) were the highest among all treatments. Under large amount of the applied N fertilizer condition, however, NPFP of N fertilizer in single season or year-round in P8 treatment was the highest among all treatments.【Conclusion】 Based on the efficiency of nutrient utilization and yields of wheat and maize crops, a larger amount of P and K fertilizers separately applied in wheat and maize crops could help synchronously to improve the utilization efficiency of three main nutrients and yields of wheat and maize crops. This can be an optimal model of main nutrient application for wheat and maize yields and use efficiency of fertilizers in wheat/maize rotation system in lime concretion black soil area of southeast Henan province or other similar ecological regions.

Key words: wheat-maize rotation system, combined application of nitrogen, phosphorus and potassium, nutrient use efficiency, yield