This paper aims to disclose the variation in water distribution and sprinkler uniformity after the canopy interception of soybean and corn. Firstly, the change laws of the water distribution and sprinkler uniformity were tested on an open field with a center pivot sprinkling machine (CPSM) operating at different speeds. Next, the intercepted water volume, the water distribution and sprinkler uniformity of the CPSM were measured at two water-needing growth stages of each crop. The results show that: On the open field, the irrigation depth of the CPSM has an approximately exponential relationship with the operating speed. The mean circumferential sprinkler uniformities were greater than the mean radial sprinkler uniformities at the same operating speeds. When the CPSM operated at 100% speed, the sprinkler uniformity at the flowering stage of soybean was 2.37% higher than that on the open field, and 2.88% higher than that at the branching stage of soybean. When the CPSM operated at 100% speed, the sprinkler uniformities at the jointing and heading stages of corn were both significantly lower than those on the open field. The sprinkler uniformity after canopy interception provides an evaluation criterion for the effect of fertilizer or pesticide application.

Continuous cropping is a common agricultural practice in Northeast China. Focusing on soybeans cropped continuously for two consecutive years, this article fully explores the effects of the amount of water, fertilizing rate, and fertilizing method on the growth and yield of soybean. Specifically, an orthogonal experimental plan was designed involving these three factors. Each factor was divided into three levels: the amount of water was set as 52.62 mm (W1), 73.41 mm (W2), and 138.6 mm (W3); the fertilizing rate was set as 6.75 kg/hm2 (N1), 9.75 kg/hm2 (N2), and 13.5 kg/hm2 (N3); and the fertilizing method was set as center pivot sprinkler (CPS) fertigation (F1), microspray (MS) fertigation (F2), and MS fertilizing + CPS spraying and leaching (F3). During the experiments, the growth traits at each growth stage were monitored, and the soybean yield was measured. The following results were obtained through the analysis of the experimental data: the amount of water significantly affects the growth traits of soybean in the early stage of growth; the fertilizing rate greatly affects the stem diameter; and the fertilizing method is a major influencer of soybean yield. The highest yield (2811.88 kg/hm2) was observed in zone 4 (W2N1F2). This means irrigation and fertilization are very important to the normal growth of continuously cropped soybean; the yield loss induced by continuous cropping can be mitigated effectively through timely and adequate irrigation and topdressing, plus fertilization by the suitable method. To prevent yield loss, farmers in Northeast China are suggested to replace continuous cropping with crop rotation. If continuous cropping is unavoidable, foliage fertilizer should be sprayed timely for topdressing at the flowering and seed-filling stages.

This paper mainly explores the impacts of different fertigation indices of center pivot sprinkling machine (CPSM) on the yield of maize in Northeast China. A total of three fertigation modes were designed: the fertigation based on the CPSM (F1), fertigation based on the micro-sprinkling system (MSS) (F2), and the fertigation mode in which the MSS sprays fertilizers while the CPSM sprays water for drip washing (F3). The three fertigation modes were combined with three water levels (W1-W3) and three fertilizer levels (N1-N3) were. First, the fertilizer uniformities of the three fertigation modes were tested. Then, orthogonal field tests were conducted to observe the growth traits and yield indices of maize in each phase of growth period, under different combinations of fertigation mode, water volume and fertilizer volume. Based on the test results, the authors identified the most significant factors and levels affecting the traits and yield in each phase. The results show that the three fertigation modes can be ranked as F2>F3> F1 in fertilizer uniformity; the highest maize yield (12,807.22kg/hm 2) and lowest maize yield (10,324.8kg/hm 2) were observed in Plot 5 (W2N2F3) and Plot 1 (W1N1F1), respectively. In general, it is recommended to adopt the combination W2N2F3 to boost the yield of maize.

Light and small sprinklers were used to irrigate winter wheat fields. The distribution and migration of water and nitrogen in soil during winter wheat growth period were analyzed. Moreover, the growth traits of winter wheat were monitored. It is demonstrated that water–fertilizer coupling effect had a significant impact on the migration of water and nitrogen in soil and the growth traits of winter wheat under conditions of light and small sprinklers. Under the same condition of irrigation quota, although the content of moisture in soil was slightly reduced with the increase of the amount of fertilizer, the impact of the amount of fertilizer on the content of moisture in soil is much more insignificant than that of irrigation quota. The content of nitrate nitrogen (NO3--N) in soil was increased with an increasing amount of fertilizer, especially when the value of irrigation quota was low. On the other hand, under the same condition of amount of fertilizer, the content of nitrate nitrogen (NO3--N) in soil was decreased with an increasing value of irrigation quota, especially when the value of irrigation quota was high. Hence, an ultra-high value of irrigation quota will aggravate the leach of nitrate nitrogen in soil. The water–fertilizer coupling effect and yield of winter wheat could be optimized by improving irrigation scheme, optimizing irrigation quota, and optimizing the amount of fertilizer.